Here I’m going to be listing some drought-tolerant plants for forest gardens. Bear in mind though, that your soil and site will be a determining factor in whether some of these actually survive and thrive or not. Our oldest forest garden has a clay loam soil – fertile and moisture retentive and slow to dry out. But in a very wet winter, Mediterranean-climate plants hate it. Things like Saltbush (Atriplex) or Acacias tend to die from wet roots there unless they are planted on a slope and in full sun. But they will thrive on a better drained soil two miles away.

Acca sellowiana (Pineapple guava) flower petals are delicious

Some of the plants listed here are not very hardy and can only be grown outside in mild regions. Even so they may not fruit – yet. An example is olive in southern England, though last year and this they have borne/will bear ripe fruit in some locations.

There are few plants listed here that will thrive in deep shade, but most will tolerate partial shade as long as they get a little sun.

If we are to adapt to rapidly changing weather conditions due to climate change, we have to push the boundaries of what we can grow. Sometimes when you do that plants won’t survive initially and may require repeated introductions until they finally make it. Weather is still variable and can damage plants when too wet or too cold. It can be frustrating, but if we wait until we are sure that a plant is going to thrive in our climate, then it is probably too late – the climate will move on.

Pinus pinea (pine nut)

Drought-tolerant trees

Trees with edible crops

Quercus ilex (Holm oak) acorns are low-tannin

Support trees and other tree crops

Acacia retinodes in flower in February

Drought-tolerant shrubs

Shrubs with edible crops

Elaeagnus umbellata ‘Amber’ (autumn olive)

Support shrubs and other shrub crops

My next post will look at drought-tolerant perennials. I will get on to looking at the flammability and fire risk/tolerance of trees after that…

Hope you soon get much-needed rain (if you need it) or sun (those in Scandinavia who have had the wettest summer.)

The sorts of trees we need are

(1) Drought/heat tolerant themselves

(2) Have sparse canopies to allow sufficient light to reach understorey crops

(3) Generally conical in shape rather than rounded depending on sparseness, to minimise shading

(4) Ideally with root systems that are not too shallow and competitive.

The latest research on drought tolerance in trees uses hard data on the leaf turgor loss point which is the point at which leaves wilt in a drought. This measurement varies a lot between families, species and even cultivars, but there is a lack of data for many species, so the lists below are not going to be exhaustive.

One generality which seems to hold is that all leguminous trees are drought tolerant, and most have sparse canopies too. Using these in the overstorey will also help input nitrogen into your growing system too. Some, though have competitive root systems which can be a negative.

Trees for the overstorey

Acacia spp. - Wattles / Mimosas

Well known evergreen nitrogen fixers from warm regions of the world. Sometimes regarded as weedy where introduced eg. The Mediterranean region. Can have quite long and competitive root systems, sometimes suckering. A .dealbata,, A. pravissima and A. rhetinodes are three of the hardiest species to try – hardy to -7 to -10 C. Small trees which are great bee plants with their yellow flowers (also in demand for floristry).

Albizia julibrissin (N) – Silk tree

Small trees in the UK, with mimosa-like leaves and yellow flowers, often used ornamentally. In warmer climates can have competitive root systems. Nitrogen-fixing, hardy to about -15 C.

Alnus cordata (N) – Italian alder

Medium to large nitrogen-fixing tree from southern Europe, very fast growing, small root systems. Hardy to between -20 and -25 C. This is the main upper canopy tree in the ART’s 32-year-old forest garden in Dartington UK.

Amelanchier arborea (F) – Common serviceberry

A small to medium sized tree 5-12m high. Can sucker. White flowers in spring are followed by small purplish fruit. The fruits are edible but not as good as from related species.

Amelanchier lamarckii (F) – Juneberry, Snowy Mespilus

A large shrub to 5m high. White flowers in spring are followed bu edible purple fruits.

Caragana arborescens (N, S) – Siberian pea

A shrub or small tree, 2-6m high. Nitrogen fixing and the yellow flowers are loved by bees; traditionally used in windbreaks. Has a dense competitive root system in continental climates. Edible seeds somewhat like lentils. Slow growing outside of a Continental climate.

Cercis siliquastrum (FL) – Judas tree

A small to medium sized tree 8-12m high with a rounded canopy. Deep rooting but not not very competitive. A legume but does not fix nitrogen. Often planted ornamentally for its show of flowers on bare branches in spring. The flowers are edible and tasty.

Colutea arborescens (N) - Bladder senna

A rounded shrub to 3m high, a nitrogen fixer and bee plant. Has a dense but small root system.

Corylus colurna (S) – Turkish hazel

Medium to large upright tree, can reach 20-25m high in time. Deep rooting, not too competitive. Has edible seeds – smaller than European hazelnuts – and is a parent of the trazel varieties.

Elaeagnus angustifolia (F, N) – Russian olive

A large shrub or small tree to 10m high, thorny, Nitrogen-fixer. Deep rooting and mnoderately competitive. Flowers loved by bees, followed by edible fruit (but not nearly s nice as from E. umbellata). Useful windbreak species.

Ginkgo biloba (S) – Maidenhair tree

Well known conical shaped large trees growing to 2m high or more. Roots deep but not spreading far. Amazing yellow leaf colour in autumn. Known for its medicinal leaves, and its non-edible stinky fruit (on female trees) containing an edible seed (though there are doubts about how edible….)

Gleditsia triacanthos – Honey locust

A large tree to 20m high or more, a legume but probably not nitrogen-fixing. Deep rooting and wide spreading root system. Slow growing outside of Continental climates. Bears long seed pods that contain an edible sweet pulp around the seeds.

Maackia amurensis (N) – Amur maackia

A medium sized tree up to 15m high, a Nitrogen-fixing legume. Shallow root system.

Maclura pomifera – Osage Orange

A large shrub or small tree to 10m high or more. Wide spreading roots. Bears non-edible fruit.

Phellodendron amurense – Amur cork tree

A medium sized broad spreading tree to about 15m high, with thick corky bark.Has a shallow, eide-spreading root system. The bark is used in Chinese medicine.

Prunus mahaleb (F) – St Lucie Cherry, Mahaleb

A large shrub or small tree growing 2-6m high, occasionally more. Wide spreading root system. White flowers are followed by thin-fleshed fruits containing a single seed. Cultivated for the seeds, ground onto the spice ‘mahaleb’. Alsoo sometimes used a as cherry rootstock.

Robinia pseudoacacia (FL, N) – Black Locust, False Acacia

A large upright tree, a thorny Nitrogen-fixing legume. Wide spreading root system. Bees love the edible flowers; foliage used for feeding sheep and goats. Can sucker especially if cut. Has hard and durable timber.

Styphnolobium japonicum (Sophora japonica) – Japanese Pagoda tree

Botanists recently changed the name of this tree to reflect that whilst it is a legume, it does not fix nitrogen. A medium sized tree to 15m high or more, white flowers in spring loved by bees. The flowers and leaves are sometimes used to make teas.

A few surprises to me came out of this little piece of research, I certainly had not thought before about interplanting Ginkgos, for example, in a food forest. This spring I planted some more Acacia dealbata in our younger food forests for increased light shade but in the future I’ll certainly consider others in the list above. When you’re thinking about which species to use, consider the space available, the amount of light the species in the understorey need, as well as whether you need nitrogen-fixation or other crops from the overstorey trees. Let’s get planting!

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Most plants start to be stressed at temperatures above 30 C, with extreme stress experienced over 40 C. As you’d expect, there is variation between species and individuals, but generally plants from higher latitudes get stressed at lower temperatures than plants from lower latitudes.

30-40 C: moderate heat stress

Effects of heat stress on plants (Image credit: https://doi.org/10.3390/stresses2010009)

Growth and crop yields slow: photosynthesis declines while respiration continues, an imbalance that can reduce a plant’s energy reserves over time.

Prolonged heat can also increase water loss through leaves and soil, leading to wilting and, in severe cases, leaf death.

Some short lived plants bolt and flower, hoping to set seed before they die (eg. lettuce). But most plants reduce or stop flowering during heatwaves, and existing blooms may drop off.

Leaves can curl, fold, and decrease their area, becoming thinned to avoid water loss by evapotranspiration.

Root systems and new aerial growth start to die back.

40+ C: extreme heat stress

For most plants (which use the C3 photosynthetic pathway) these temperatures are nearing the limits they can survive.

For these, heat scorch, death of new growth and death of whole plants ramp up as temperatures rise above 40 C. Younger plants are usually more vulnerable to damage and death.

Wheat and barley, for example are likely to suffer severe damage at 40 C and die at about 45 C. Fruit on apple trees will experience sunburn at 38 C and even with protectant clay-based sprays will suffer severe damage at 43 C.

A small group of plants use the C4 pathway and can tolerate higher temperatures without becoming so heat stressed. These include maize, pearl millet, sorghum, sugarcane, grain amaranths, most tropical pasture grasses, and miscanthus. Perhaps we should be growing amaranth instead of wheat?

Amarathus cruentus, one of 3 species used as grain amaranths

How can we help our plants survive heatwaves?

• Use agroforestry systems. The shade from higher trees and shrubs will reduce heat stress effects on lower plants. In addition, the hydraulic lift effect by trees means that the soil will dry out more slowly in the root zones of trees. Forest garden / food forest systems, once established, tend to be resilient in heatwaves, with temperatures under the canopy several degrees cooler (as it is in woodlands).

• Increase soil organic matter and therefore the water-holding capacity of the soil. Tree-based systems will do this anyway, but you can also use woodchip mulches, any organic matter etc.

• Don’t prune back apparently newly dead growth in summer, but wait until the following spring, as there may still be live buds on some growth.

• If you have to irrigate, do so less often but making sure the water percolates deep. Use a tensiometer to check moisture levels deep down.

• Grow more plants from lower latitudes

• Give plants from higher latitudes (including native plants) some shade in summer by interplanting taller trees and shrubs with thin canopies to the south and west of susceptible plants. Highest daytime temperatures tend to be through the afternoon, so that protection from morning sun is less critical.

• Grow plants in appropriate locations! Obvious really, but if it’s a woodland plant then grow it in a shady spot. Ferns are a good example, being very susceptible to heat damage. Other plants often grown in sun that really do need shade in a heatwave include Fuchsias and Magnolias.

• For shade trees and large shrubs, choose species with smaller compound leaves as these get less heat stressed than trees with larger single leaves, and also tend to have fairly thin canopies which let some light through. Legumes are particularly good in this respect. Think Acacia, Albizia, Caragana, Colutea, Gleditsia, Gymnocladus, Laburnum, Maackia, Robinia, Sophora.

  

  Gleditsia triacanthos

Just like humans, most plants are going to need some shade just to survive in future summer heatwaves. Tree-based growing systems are not just desirable but are going to be critical for our future.

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The genus Malva consists of some 30 species of annual and perennial herbs and subshrubs from temperate and tropical regions. Easily grown, and often found in ornamental flower borders and naturalistic plantings, Malvas are some of the finest perennial salad plants for temperate climates, and we use several species in the A.R.T. forest gardens in Devon, UK.

General description

Mallows are found in the wild in open sunny habitats, on waste ground, along roadsides and hedge banks, in woodland clearings and in pasture or grassy meadows.

The alternate leaves of Malva species are very varied, often on the same plant there will almost round leaves near the base, with leaves becoming more and more finely crenulated higher up the plant. This can make identification from the leaves only difficult. The hardier perennial species often retain a rosette of basal leaves well into the winter, or in mild winters all through the winter.

Flowers are usually white, pink or purple, with 5 petals, often quite showy, lasting for a week or more.

Seeds are borne in tight heads.

Malva are anchored by long vertical tap roots.

Malva species have been called by the curious names Cheese (or Cheeses), Cheeseflower, or Cheese-weed, with numerous plays off the same idea, including Cheese-cake, Dutch Cheese, Doll-cheeses, Fairy-cheeses, Pick-cheese, or Cheese-log. This is due to the wheel-shaped carpels that remain after the flower petals fall, which is supposed to resemble miniature cheese wheels, small enough for use by the fairies…..

Malva sylvestris seeds in “cheeses”

Some species of Malva are considered nuisance weeds, for example in Australia with M.sylvestris.

Uses

The major use for Malva species is as salad plants. Probably all species can be used in the same way, though the known ones are listed later. The leaves make an excellent base ingredient in salads – they are not highly flavoured, but have a pleasant mucilaginous texture. The texture of the lower rounder leaves is best; as the plants grow and flower the finely cut leaves higher up become more course. It is best to grow an area of several plants to make harvesting efficient, something like ten plants would yield 2 daily portions of salad base.

Leaves can also be used cooked – my favourite way to use them is in the Georgian cakes or rolled balls made from the walnut paste nigvzis sakmazi and the walnut spread phkali.

Note: the leaves are normally perfectly safe to eat, however if plants are cultivated with the use of excess nitrogen, particularly with soluble nitrogen fertilisers, plants can accumulate excess nitrates in their leaves (as can lettuces and other plants) which are not wholesome.

The flowers are equally edible, with a mild flavour and slightly mucilaginous texture. The whole flower can be picked or just the petals – the green base can get a little course. I often sprinkle the petals over the top of a salad.

The leaves can be cooked in soups, stews etc. although the texture can go somewhat slimy; they have a thickening effect. Mallow soup is highly prized in the Middle East, and mallows are widely used there as cooked greens (they get a great mention in Sami Tamimi’s recent book Boustany: A Celebration of Vegetables from My Palestine.)

M. sylvestris leaves & flowers

The young immature seeds can be eaten – they have a pleasant nutty flavour – however they are small (2 mm) and fiddly. An edible oil can be extracted from the seeds.

Many mallows have long been used medicinally as the leaves are demulcent and anti-inflammatory.

Similarly, the stems of many mallows can be processed to extract a strong, coarse fibre to make cordage (string, rope).

Bees are very fond of the flowers.

Cultivation

Malva spp. are undemanding in cultivation, they grow in any reasonably drained and moderately fertile soil.The do require full sun or dappled shade. The perennials tend to be short lived, often 3-4 years, though plants often self sow if there is bare soil for the seeds to fall on to.

Grow from seed, either sow seed direct in the ground or use deep containers to grow in – because mallow have long tap roots.

Taller species grown in very fertile soil may flop over after heavy rains and/or winds.

There are some named varieties which have been selected for their showy flowers.

Mallows sometimes suffer from a leaf rust during hot dry summers when plants are under stress. The other common problem is capsid bugs damaging leaves, leaving small holes and distortions, but in a diverse garden this should not be a serious problem.

Do not fertilise – excess nitrogen fertiliser can cause excessive nitrate levels in the leaves.

Propagation is usually by seed, and is easy. Just sow seed in spring in seed trays and keep warm; seedlings can be potted up and are large enough to plant out in summer if required. Annuals can be sown in situ in spring.

Softwood cuttings can also be taken in spring.

The species

The species listed here are the ones with known and recorded uses. There are several other species, including 4 Mediterranean annuals (M.aegpytia, M.cretica, M.hispanica, M.stipulacea), which may have similar edible and medicinal uses.

Malva alcea – Hollyhock mallow

Bushy perennial herb to 80 cm high and wide. Lower leaves rounded with wavy edges, higher leaves finely cut. Flowers, 25-40 mm across, are borne singly in leaf axils at ends of branches from July-October, pink. Native to southern Europe, naturalised in the USA. Hardy to zone 4.

‘Fastigiata’ – to 1 m high, narrowly upright, flowers deep pink.

Malva alcea in flower

Uses

Excellent salad plant.

The seeds are reported to yield 15% oil.

Leaves used medicinally for mouth infections.

A fibre can be obtained from the stems for cordage.

Dyes can be obtained from the plant and seed heads.

Malva excisa

Perennial to 120 cm high. Flowers from July-October. Native to Europe, Hardy to zone 4.

Uses

Salad plant.

The seeds are reported to yield 15% oil.

Leaves used medicinally for mouth infections.

A fibre can be obtained from the stems for cordage.

Dyes can be obtained from the plant and seed heads.

Malva meluca

Annual from southern S.America, growing to 120 cm high.

Uses

Salad plant.

The seeds are reported to yield up to 20% oil which has been used in soap making.

A fibre can be obtained from the stems for cordage.

Dyes can be obtained from the plant and seed heads.

The plant has been used for fodder.

Malva mohileviensis

Annual growing to 120 cm high.

Uses

Salad plant.

A fibre can be obtained from the stems for cordage.

The seeds are reported to yield up to 20% oil which has been used in soap making.

Dyes can be obtained from the plant and seed heads.

Malva moschata – musk mallow

Malva moschata showing variation in leaf form

‘Alba’ – to 60 cm high, flowers white, leaves deeply cut.

‘Rosea’ – flowers rose tinted purple.

Uses

Excellent salad plant.

A fibre can be obtained from the stems for cordage, textiles and paper making.

Dyes can be obtained from the plant and seed heads.

Medicinally, all parts of the plant are antiphlogistic, astringent, demulcent, diuretic, emollient, expectorant, laxative, salve. The leaves and flowers are the main parts used, their demulcent properties making them valuable as an anti-inflammatory for bruises, inflammations, insect bites etc, or taken internally in the treatment of respiratory system diseases or inflammation of the digestive or urinary systems.

Recent screening identified the seeds of Malva moschata as having an antibacterial activity against five bacteria including E.coli and Staphylococcus aureus.

Caterpillar & butterfly forage.

Malva neglecta – common mallow, dwarf mallow, round leaved mallow

Annual to 50 cm high. Leaves roundish on long stalks. Flowers in clusters from leaf axils, pink or white, July to September. Native to Europe, NW Africa, SW Asia, naturalised in the USA. Hardy to zone 5.

Uses

Good salad plant. It is also extensively cultivated on the banks of the Nile in Egypt as a potherb.

A decoction of the roots has been used as an egg-white substitute for making meringue.

Medicinally the plant is used identically to M. moschata.

Malva nicaeensis – Bull mallow

Erect annual or short-lived perennial to 50 cm high. Leaves roundish, lobed. Flowers single or in clusters from the leaf axils, July to September. Native to the Mediterranean (Arabia to Iran and S.Russia), naturalised in Europe and the USA. Hardy to zone 7.

Uses

Salad plant.

Dyes can be obtained from the plant and seed heads.

Malva parviflora – Cheeseweed, Least mallow

Annual growing 50 cm high. Native to SW Europe, naturalised in Britain.

Uses

Salad plant.

The leaves are used to make a soup resembling pea soup.

The seeds are reported to yield up to 18% oil.

Dyes can be obtained from the plant and seed heads.

Medicinally, The whole plant is emollient and pectoral. The seeds are demulcent and are used in the treatment of coughs and ulcers.

Malva pusilla – Small mallow

Annual growing 30 cm high. Flowers July-September. Native to Europe, naturalised in Britain. Wind tolerant.

Uses

Excellent salad plant, though quite low yielding.

Dyes can be obtained from the plant and seed heads.

Medicinally, the leaves are demulcent and have occasionally been used internally in the treatment of inflammations of the digestive and urinary systems; and externally as a poultice for bruises, inflammations, piles etc. The seed is demulcent and is used in the treatment of coughs, bronchitis, ulceration of the bladder and haemorrhoids; it is applied externally in the treatment of skin diseases.

Malva sylvestris – Wood mallow, tall mallow, cheeses

Erect annual, biennial or perennial to 1 m high. Leaves broadly heart shaped, lobed. Flowers borne in clusters from the upper leaf axils, pinkish-mauve, June-October. Tolerates slightly more shade than other mallows. Native to Europe, N Africa, SW Asia, naturalised in USA. Hardy to zone 5.

Malva sylvestris var. mauritiana (High Mallow) is native to Iberia, Italy & North Africa. It has in the past been regarded as its own species (M.mauritiana). The variant has larger flowers & larger leaves.

‘Alba’ – to 75 cm high, white flowers.

‘Brave Heart’ – upright to 90 cm, large leaves, large flowers – pale purple with dark eye.

‘Cottenham Blue’ – to 75 cm, flowers pale blue, early flowering.

‘Primley Blue’ – prostrate to 20 cm high, flowers soft violet.

Uses

Excellent salad plant. M.sylvestris var.mauritania is reputed to have the tastiest leaves, though it is less hardy

Wood mallow leaves make one of the best soups of all wild greens.

Dyes can be obtained from the plant and seed heads.

Medicinal uses identical to M.moschata.

A tincture of the flowers forms a very delicate test for alkalis.

A fibre can be obtained from the stems for cordage, textiles and paper making.

Caterpillar & butterfly forage.

Malva verticillata – Chinese mallow, Whorled mallow

Erect annual or biennial to 1.8 m high. Leaves roundish, lobed. Flowers in dense clusters in leaf axils, white or purple, July-September. Native to Europe & Asia, naturalised in Britain and the USA. Hardy to zone 6.

‘Crispa’ (salad mallow, curled mallow, Castillian mallow) – upright habit, to 2 m high, leaves wavy edged, flowers pale lavender colour, small.

Uses

Excellent salad plant (this one even makes it into semi-mainstream salad books.) It is grown on a limited commercial scale in China.

Dyes can be obtained from the plant and seed heads.

Medicinally, the seed is demulcent, diuretic, emollient, galactogogue and laxative. The leaves and stems are said to be digestive and were given to women in the advanced stages of pregnancy.

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In Europe, warming is about double than the global average, so in the immediate future likely to be about 0.7°C per decade. Already in Europe we have had a shift of growing zones of about 60 miles (100km) per decade northwards for the last 4o years at least, a total shift of 240 miles (400km) or more [2]. The figures are a bit higher in Eastern Europe than Western.

The past 40 years has seen climate shifts equivalent to

Glasgow => Manchester

Manchester => London

London => Paris

Devon (where we are based) => Nantes, France

The rates of these shifts are expected to increase, perhaps double from now on: ie by 2040 a further shift of 180 miles (300km). This is a useful (rough) figure as we can now look that far south and see what crops are being grown there now as likely candidates for us.

The risk of late spring frost damage, however, has increased so introducing very early flowering crops comes with that risk – their planting location is critical.

Planning tree crops for the future

As I wrote here last year, one key strategy is diversity. In terms of trees this means

• Pushing the boundaries of what will grow for you. The weather will change differently in different regions of course, but generally, including warmer-region species in your plantings will be advantageous long-term.

A farm in the East of England is starting to grow lemons and olives

• In North West Europe (eg. the UK where we are) there is a long term risk that the AMOC circulation might fail, and all the warming we’ve had to date will be wiped out, to replaced with a modest cooling (or perhaps no cooling, depending on how much warming we’ve had by then). In regions like this it makes sense to retain some traditional tree crops that are used to colder conditions.

Apple orchard

• Many fruit trees are grafted onto rootstocks to control size and allow planting in different soils. Start looking at rootstocks from warmer regions which will be better adapted for your conditions in the future. The rootstock can have an effect on leafing time in spring amongst other things, and will have its own requirements for winter chill. There is an issue of supply, with very few commercial rootstock growers.

• The fruit varieties grafted onto rootstocks also have their own chill requirements. The number of chilling hours (ie hours in winter under 7°C) have been reducing almost everywhere for the last 60 years, which also means that older traditional varieties are gradually becoming less well adapted to where they are historically grown. This means we should be looking for lower-chill varieties for the future, which in practice means looking to varieties of those fruits that do well in warmer regions. Some fruit trees are quite easy to regraft in situ with a new variety. Note that lower-chill varieties are likely to leaf out and/or flower earlier so may be more frost prone in the near future.

• In forestry, trees are nearly always seed grown. Foresters and forest tree nurseries need to be looking for more southerly provenances of tree seed for some or most of their trees (although earlier leafing can increase frost issues). There is a bigger problem, which is the rotation time to harvest. Fast rotations of 30-35 years are possible with crops like sweet cherry and hybrid walnut, and these have the least risk in terms of climate changes. Longer rotations are much riskier. Coppice or pollard systems which work on shorter rotations are going to be more certain in the near future

  

  Hybrid walnuts in Devon, UK.

• Accepting that we might need to replant or regraft trees more often, perhaps on a timescale of 10-20 years (actually 15-20 years is common now in dense commercial orchards.) Because of the compressed timespan, trees on more vigorous rootstocks (like those used in traditional apple orchards) are becoming more of a risk, because they can take 10 years to even start fruiting.

It’s important to realise that by maximising diversity, we are not maximising overall yields. Instead, we are safeguarding moderate yields. By pushing the boundaries of what we can grow, some tree crops will inevitably fail some years.

Increasing diversity also addresses the pest and disease issues which will grow as new pests and diseases spread from warmer to cooler regions.

Coping with weather extremes

Whilst increasing temperatures have a significant effect on tree crops, it is the increase in extremes, rather that gradually changing climate, that is most damaging to plants. In many places including here that is likely to be winter storms, excessive winter rain, summer drought and heat.

For tree crops strategies should include:

• Using rootstocks which are tolerant of dry or wet conditions

• Increasing soil organic matter will buffer against both very wet and very dry conditions. Add mulches of plant materials, woodchip etc.

Woodchip mulch beneath apple trees

• On clay soils, improve drainage by installing physical drains.

• Plant more or beef-up existing windbreaks. Rely less on a single line of windbreak trees/shrubs, and less on a single species in a windbreak. Include some evergreen plants if possible.

• On heavier soils, look at trees that tolerate waterlogging

Swamp cypress trees

• On light soils look at trees that are drought tolerant

Download a list of wind tolerant trees, trees that tolerate waterlogging and trees that tolerate drought (these are extensive but I make no claim about completeness!)

Trees And Shrubs

42.8KB ∙ XLSX file

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Conclusions

There are no easy answers to climate change adaption! The clue is in that last word, we have to be very adaptable now and in the future, be open to trying new crops and accepting that some old favourites may not be worth growing any more where you are.

Going forward, dialogue between researchers and growers is really important, and one example of this is the Third International Food Forest and Forest Garden Symposium which is an online event we are organising in November this year. This will be an exciting gathering of food forest practitioners, researchers, educators, chefs and others interested in sustainable food and growing. The website and booking has just gone live HERE so do have a look!

Lastly, if you’d like some music to work to as you plant or weed your new trees, you can listen to my new album HERE

[1] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2025GL118804

[2] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019EF001178

The weather records being broken right now here are for rainfall. Winter rainfall has always been significant in the UK, especially in the West, but in recent decades it has been gradually ramping up. The result is more floods and very wet ground which is damaged really easily by livestock, human foot traffic or vehicles. Many farmers ending up losing patience in spring and working their fields when they are still too wet to do so without causing serious compaction damage (incidentally reducing the ability of soils to store carbon).

The rain isn’t a problem for alexanders (Smyrnium olusatrum) which has been growing strongly all winter. The leaves are strongly-flavoured like lovage/celery and make their way into our stews, soups and casseroles.

“Power corrupts” seems truer than ever these days and we all need to start taking measures to adapt to the changes coming, whether or not officialdom endorses our efforts.

As you’d guess, I’m of the opinion that tree-based cropping systems are the future. There should be no field anywhere in the world without at least some trees or perennial crops in it.

Forest gardens are probably the most sustainable growing systems on the planet. But this is where the strengths and weaknesses of scientific methods come into play. If we wait for enough absolute scientific proof that agroforestry and forest gardens can feed people, protect soils, encourage biodiversity, store a load of carbon, improve people’s mental health etc. then we are going to be too late. There is already enough proof that agroforestry methods work and if there are more delays in implementing then things will get that much worse before mitigation efforts kick in.

Wild garlic (Allium ursinum) has just started to come up this week. We’ve been eating Neapolitan garlic (Allium neapolitanum) leaves all winter but will relish harvesting these in a few days time.

It also struck me that in many ways forest gardening is a repudiation of the right-wing fascism that is rising in the US, UK and other countries. It is no surprise that there is a history of fascist movements appropriating ideas that native plants are always the best.

Forest gardens are living examples of diversity and internationalism. Plants have to jostle together and get along (I’m not pretending there is never any competition, but reducing that to a minimum is one of the arts of forest garden design). They come from all parts of the world (I’m talking about a UK perspective here, where we have such a poor “native” edible flora that if you wanted to make a native-only forest garden then you’d starve). We use plants from six continents in our gardens. Diversity is really important and indeed is the very basis of resilience to pests, diseases and anything the weather throws at us.

Turkish rocket (Bunias orientalis) also seems immune to the rain and stays evergreen here.

So there is no time to lose. Planting in a long-term growing system is one of the most positive things you can do to counteract the doom and gloom. With trees you are not just planting for yourself but for future generations too. What better strategy for keeping sane in an insane world?

Fungi thrive in our wet mild conditions. These bracket fungi are colonising a dying broom plant (Cytisus scoparius) that has been used as a successional nurse plant in one of our forest gardens.

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Well, 2025 has been an interesting year, to say the least.

I started the year with a substack blog emphasising the importance of adaption to climate change, and I’ve noticed through the year that more and more people are saying the same thing. In late summer I did a talk to farmers at the UK Agroforestry Show – this was in the middle of one of the worst droughts for years – and decided to pull no punches: I said that it’s only a matter of a few years until we have similar summer droughts in successive years here, that growing annual crops without irrigation will become increasingly unreliable, and that adaption and perennial crops is the name of the game. There were no dissenting voices.

Sweet cicily

Back in the spring we had the shock when the landlord of our 31-year-old forest garden (Dartington Hall Trust) attempt to give us notice to quit the site. Overall I am big sceptic of social media but to see the size, speed and vigour of the protest against this move fuelled by easy sharing was an eye opener. DHT backed down, and in fact it turned out that what they were trying to do was not legal in any case. Our lease runs for another 3 years, and after that rolls on yearly unless notice to quit is given again. DHT got their fingers burnt once and hopefully they won’t want that to happen again….. In any case I am no longer stressed about the situation: what will be will be.

Korean celery

The drought conditions in Devon were not quite as severe as further East, and there were few signs of drought stress until early autumn when a few of the perennials in our younger forest gardens looked a bit ragged. In fact it was an exceptional fruit year when almost everything from gooseberries and apples to pears, plums, persimmons and walnuts had bumper crops. The rain came in torrents by November, with the River Dart bursting its banks and cutting off access to one of our sites for a bit.

Neaplolitan garlic and wild strawberries

We haven’t had much cold weather at all up until now, so lots of things are still in leaf and harvestable. Sweet cicily, Korean celery, Neapolitan garlic, mandarin balm, goji leaves all looking good today. The bush quinces are flowering. Some of the hazel catkins are near to shedding pollen – I do wonder about that, hazels were one of the few crops not to do fantastically well this year: perhaps the pollen is being shed over a much longer period and coinciding less with the female flower receptivity?

Mandarin balm

One other big change just happening is that we’re selling our plant nursery to Fran Welch, who has worked for us for several years and will continue the legacy of growing a huge range of interesting edible plants. After running the nursery for 25 years it feels appropriate to hand on to a new generation to take things forward. The nursery will be called the Edible Canopy (www.ediblecanopy.com) and will be operational from January. We wish Fran the best of luck.

Goji

Selling the nursery won’t affect the other aspects of the ART: we still have 4 forest gardens to look after, tours and courses to run, books to write and sell, seeds to supply. So there will be plenty to do. But the time liberated for me by not having a nursery to run will enable me to do more consultancy and also spend more time on my music (Altai Dawn).

Hazel

Also in 2026 there will be the 3^rd symposium to organise and run in November. This should be a great forum to share ideas about food forests and forest gardens, including aspects of education, design, research, perennial foods etc. The vibe of the previous symposiums was great, really feeling like a coming together of enthusiasts and important too for many of us in the field work mainly on our own and easily forget there are lots of others doing similar things across the world.

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Favourite book of the year: 21^st Century Yokel by Tom Cox – a lot of which is describing South Devon here. Check out Tom’s Ghost blog too.

Favourite track of the year week: Calculer by Sousou and Maher Cissoko.

Favourite substack: Mark Diacono’s Abundance

Artichokes having a bad hair day

Medlars ripening on the tree. We haven’t had any frosts in the last month so it’s just the warmth that has ripened them.

Raspberries and strawberries flowering. They won’t come to anything of course but the plants are confused enough to give it a try.

Also flowering is Japanese quince (Chaenomeles). Its certainly warm enough for bees to be around (16 C today) although the rain has put them off.

Korean celery (Dystaenia) is looking lush. Behind it here you can spot sweet cicily also looking good. In front the edible leaves of Scorzonera.

Mandarin balm (Melissa ‘Mandarina’) is not showing any signs of going dormant. This variation of lemon balm with mandarin-flavoured leaves is lower and more spreading and makes a better ground cover.

Monk’s rhubarb (Rumex patienta) putting up new leaves. Although they look suspiciously dock-like, the leaves of this species are a really good sorrel.

Here in Devon we’re not really subtropical yet, but our winters are getting so mild that a minimum in winter of -2 or -3 C means that the character of some plants is changing: some herbaceous plants are becoming evergreen, a case in point being wild strawberries (eg. Fragaria moschata and Fragaria vesca) which were reliably herbaceous 30 years ago. Others, like some of the above, are getting a whole new flush of growth in late autumn. Some deciduous trees are holding on to their foliage really late - until December or January. Each year brings some new surprises, and no-one has researched which plants are likely to change behaviour: at least we know that we don’t know what is going to happen in the next 10 or 20 years. Welcome to climate change!

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Tree vegetables is a term you don’t often hear in our culture - indeed eating leaves or shoots off trees is still regarded as a bit odd, or the realm of the intrepid forager. But in other parts of the world it is entirely normal to use trees for food in this way.

As part of ART I've long grown and eaten tree veg but it wasn't until I read the excellent paper by Eric Toensmeier et al on the nutritional content of perennial vegetables (*) that I realised just how nutritious they are, coming in some of the top places in the nutritional league amongst hundreds of alternatives including annual veg.

Why tree leaves and shoots are quite so high in nutrients hasn't been researched, but it seems highly likely that it is because woody plants form the best associations with mycorrhizal fungi. These fungi are critically important (indeed we would not be here without them) and have many ecosystem roles. They form symbiotic associations with many plants (especially trees), attaching to and inserting themselves inside tree roots. These fungi are much better at accessing nutrients in soil than plant roots as their mycelial networks are finer (a tenth the diameter of the finest plant roots) and more extensive. The fungi pass various nutrients to the tree and are rewarded with sugars going the other way. As a result of this extra source of nutrients, tree leaves and shoots seem more likely to have higher nutrient levels.

Management of trees as a leaf or shoot crop usually entails a regular trimming or cutting regime (often coppicing or pollarding) to make the harvesting practical and to maximise the crop of young growth.

Here are the best tree veg to grow in our temperate climate:

1. White mulberry

All mulberry leaves are edible but white mulberry and its hybrids have the best texture. Very young leaves can be used raw but mostly use as a cooked leaf. You can harvest leaves right through the growing season: late into leaf, so this is usually June onwards until the first frosts. Last year we were picking all the way through to early December as the autumn was so mild.

White mulberry leaves have more protein (10% in fresh leaves) than almost any other leaf on the planet (that’s about 4 times the amount in annual spinach). They have high levels of calcium, iron, magnesium, zinc and Vitamin C.

You can eat the leaves (if you can reach them) of a larger tree grown for its fruits, but we prefer to grow trees for fruit separately, and pollard our mulberry trees at about 1.2m /4 ft height every winter, which keeps the plant as a bushy shrub 2m in diameter.

2. Toon

Gradually becoming better known, toon (Toona sinensis) is a Chinese tree whose leaves are widely used where native. They have a unique strong flavour of vegetable stock – onions, garlic and spices. The young leaves can be used throughout the growing season raw in salads or cooked. The older leaves can be used cooked (removing the central rib as it can get tough) although they are not quite as flavourful. We also dry the young leaves and rub into a leaf powder to use like bouillon powder in winter: they lose some flavour when dried but are still good.

Toon leaves are high in Vitamin A, Vitamin E and several other minerals.

Manage the trees by coppicing or pollarding – we use a one year cycle of cutting as they are very vigorous. Or you could do an all-over annual trim to keep bushy.

3. Vine

It was a revelation to me to find out just how nutritious grape vine leaves are. They are very high in many nutrients and exceptionally high in fibre.

Most of us have probably eaten vine leaves as you’ll find all around the Mediterranean, using the older leaves (which have usually been preserved in brine) as a wrapping for a parcel of food. However, younger vine leaves are a good vegetable themselves, cooked in stir fries and the like, with a slightly sour lemony flavour.

If you’ve ever grown a grape vine you will know that once established, they produce masses of foliage (and this is what vineyards spend their summers pruning off so sun gets to the grapes). If you are actually growing grapes for the their leaves they are one of the easiest plants to grow: they tolerate quite a lot of shade, and the young leaves can be harvested all through the growing season. The plants are kept as bushes by regular harvesting.

It's important to grow pure European varieties (Vitis vinifera) for leaf production, as the leaves of most hybrids (of European and American or Asiatic species) have thick furry leaves of poor eating quality. Our taste tests identified Chardonnay as one of the best for its leaves.

4. Goji

Goji berry (Lycium barbarum) is a spreading pioneering bush which can tip layer and grow into larger colonies if allowed. Best known for its edible (though bitter) fruits, the leaves are a widely used vegetable in China.

The leaves don’t have a big flavour but are very high in vitamins A and E, and are used cooked. We add them to soups, stews etc.

Because goji bushes are very vigorous, there are plenty of “spare” shoots and leaves. We mainly harvest in spring and again in autumn, finding that the leaves in summer can be a bit tatty or mildewed. We’ll often strip whole branches of their leaves if they seem excess to requirements.

Goji bushes require pruning in any case to keep as an upright shrub 1-2m high, so no extra pruning for leaf production is need.

5. Saltbush

Mediterranean saltbush (Atriplex halimus) is a grey-leaved evergreen shrub a couple of metres high. The leaves can be harvested all-year-round and a pleasant slightly salty taste, and are high in many nutrients.

The main issue with growing saltbush is the hardiness. It’s only hardy to around -10C and only then if it’s in a sandy soil. We’ve lost it several times over the years but keep on planting it as it’s such a nice leaf available when others are not.

6. Lime

All young lime (Tilia spp.) leaves are edible, and small-leaved lime (T.cordata) is our favourite for the leaf texture. They are very high in Zinc amongst high levels of various minerals.

Lime trees all get large with age, not a useful trait if you want to be harvesting lots of leaves, so are usually coppiced or pollarded to keep bushy. The plants then become bushy rounded shrubs, size about the same diameter as the cutting cycle – most of ours are on a 3-4 year cutting cycle and can get 3-4m wide and high.

All these leaves can also be dried through the season for use in winter. Dried leaves can be added whole to soups, stews etc. or crumpled into a leaf powder. Sometimes the leaf ribs can be rather tough when dried so crumbling allows these to be easily filtered out.

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Because these plants are kept small by management, they can fit into any size growing areas, even small gardens. So what are you waiting for?!

*Eric Toensmeier, Rafter Ferguson, Mamta Mehra (2020). Perennial vegetables: A neglected resource for biodiversity, carbon sequestration, and nutrition. PlosOne.

https://doi.org/10.1371/journal.pone.0234611

This forest garden really does act like an ecosystem now, and is completely untroubled by the dry weather. In the fields 150m away, the ground is cracked but not so here, for although we started with the same soil as in those fields, the system has changed it since and it now full of organic matter, incredibly diverse fauna, and rich symbiotic mycorrhizal fungi. If you grow these systems then you are not stuck with the soil you start with, the system transforms it into something very special.

On another site, our oldest nut orchard (28 years) is really quite grand now. The sweet chestnut trees hold a stately canopy over the coolness below – it feels like a chestnut forest.

The chestnuts have just finished flowering and are already growing tiny burs for the autumn. They get pollinated by wind, bees, flies and other insects – anything goes really – and the dry conditions should ensure a bumper crop this year.

The shade from the walnuts is more dappled, they are the same age as the chestnuts but are quite a bit smaller as they are slower growing. Probably my favourite heavy-cropping nut, they sometimes suffer from bark stripping by the pesky grey squirrels, but this year so far the grey menaces are few and far between, maybe it’s been too dry for them. Last winter, 4 miles north of here, pine martens (the very best biological control for the squirrels) were legally released and are apparently already coming this direction. I can’t wait.

In a sunnier spot on this site the persimmons have been flowering well too. It’s a fruit we’re not used to growing in England but is becoming more and more productive with climate change.

When it gets too hot we retreat to the shade and maybe process some fruit (the first apples, cherry plums and plums are all in, earlier than ever) or maybe crack some nuts. Or for me there’s the allure of the computer for the inevitable admin or sometimes more interesting tasks such as this. This afternoon is hot and humid and I’m sharing my office desk with Dart – how I wish I could chill out like that!

We have a second site on the Dartington Estate - apart from the forest garden we have a trials site which is dominated by nut trees. We’ve had this site 28 years and as well as the common nut trees (walnuts, hazels, sweet chestnuts) we have heartnuts, butternuts, black walnuts, hickories, pecans, chinkapins, pine nuts and monkey puzzle/chile pine trees. As you’d expect, autumn is busy on this site and in spring there isn’t too much work to do after the brambling season has finished.

I was walking around this site last week and came across this:

Yes, it’s a dead money puzzle (Araucaria) tree which has toppled a year or so after the leaves turned brown.

One of the facts about experimenting is that sometimes you fail, and the Araucarias have made that clear. I planted 7 trees here some 24 years ago. Because monkey puzzle is dioecious (with male and female flowers on different trees) it is essential to plant a group to be able to get nuts. Even with 7 trees there was a 1/64 chance that they would be all male or all female and be useless from the nut production point of view, but that seemed a small enough risk to take.

They grew well (that’s my way of covering the intervening years) and the first started flowering after 19 years. Fantastic, it turned out there were males and females present. But just as they started to crop - the nuts are borne in football-sized cones, each holding several hundred pointed nuts - the trees started to die. One by one they turned brown and perished. I have not found the cause but it is obviously some soil-borne disease, maybe a Phytophthora fungus as the damage started after a series of extra wet winters; the trees are on a sloping site in a clay loam soil normally pretty well drained. But climate change is making our winters here wetter and this probably contributed to the damage.

The crops we did get were used fresh (cooked rather like chestnuts) and also dried to make Araucaria flour which is rather delicious.

There are two trees left standing (a male and a female) but one is already turning brown so they will be doomed and it is unlikely we’ll get another crop from them. I don’t regret planting them, it’s just one of those things. When they are gone it will give two stone pine trees (Pinus pinea) more space to thrive.

Meanwhile on another site we have a forest garden greenhouse. This was constructed using many of the ideas pioneered by Jerome Osentowski in Colorado, particularly the heat storage system. This uses fans and a series of underground air pipes to store heat in the soil from spring to autumn, then release the heat in winter to keep the whole place frost free. It works pretty well and although it has been down below zero (C) sometimes, it hosts a subtropical forest garden which lifts our spirits when the cloud and rain stop us from seeing the sun for days or weeks on end.

Some of the tree-sized plants we grow in there include avocados, bananas, custard apples, papaya relatives, jelly palm, strawberry guava, pomegranate ad lots of Citrus - satsuma, clementine, mandarin, lemon, thai lime.

Last autumn we spotted a banana flower on our Blue Java banana. Excitement was tempered by the fact that the flower would have to go through winter and near-zero temperatures to be able to continue flowering and fruting this year. Luckily, it did, and not only that but a second flower has formed on the same banana clump:

So in 4-5 months we should have bananas to eat - experiment permitting. And for the first year there are custard apples on the tree …… just waiting for the avocados now.

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Dartington Hall Trust (DHT) have given a years’ notice to end the lease for a groundbreaking 2 acre food forest project which has been under way on the Dartington Estate for 31 years, despite it costing them nothing; whereas it has brought in over 50,000 visitors to the estate, hosted important scientific research on carbon storage, and become what is often described as the best example of a food forest (or forest garden) in the temperate world.

Groundbreaking work by agroforestry pioneer

Martin Crawford, founder and director of the Agroforestry Research Trust, the charity which has leased the land for 31 years, says:

“We’ve put in decades of work to achieve this exemplar of a food forest system. This seems like a complete betrayal of trust by the DHT, who are only looking at money – they have given us no reasons but think they can get more money by flattening and building there or using it for something else instead of the rent we pay.”

A food forest or forest garden is a complex agroforestry system using trees, shrubs and perennial plants to mimic an ecosystem but with lots of crop plants. Think fruit and nut trees underplanted by fruiting shrubs and vegetables. They are very sustainable systems to grow food and store carbon at the same time. The food forest at Dartington has inspired the creation of thousands of such systems throughout the world, and more recently has inspired the Royal Horticultural Society to diversify their plantings at Wisley, and the National Trust to start its first forest garden at Shugborough.

Martin continues:

“Our charity and the DHT have had a long association with the understanding that ours is a long term land-based project which after 31 years still has a long way to go. For example, long term measurements of carbon storage in such systems are vitally important in climate change research.

DHT have had many other benefits too. We’ve brought some 50,000 people to the Estate, many of whom have gone on to use the accommodation or catering facilities. Over the years the DHT have used our name to get kudos for doing ecologically sound projects on the Estate.

“Ecological vandalism”

“Throwing us off is not the same as giving a tenant in a building notice – they can easily move. This food forest is irreplaceable. It is literally priceless. What the DHT are doing is ecological vandalism.

I had thought there was still a thread of ethical behaviour at DHT but was clearly mistaken. DHT are not breaking any laws giving us notice but it is still unethical, amoral behaviour breaking 31 years of trust between our organisations. Some of their communications have been casual, disrespectful and with a feudal tone too, rubbing salt into the wounds. Their calculations may well turn out wrong if an economic boycott takes place.

It’s even more galling, because we obviously need a secure long term tenancy, and we spent 4 years negotiating this with DHT and had a verbal agreement to go ahead with the last CEO Alan Bolden. Then with regime change the DHT reneged on that agreement and refused to give us a long term deal.

A lot of people have visited this food forest and know how valuable it is. Please protest this decision by writing to the DHT (see below) and tell them what this space means to you and what it’s loss to the wider world means; and why they should give us long-term security.

To the Dartington Trust I say: please reconsider your actions. As well as retracting this decision, we need a long term secure lease or ideally to buy our site. This kind of behaviour will lose you a lot local support. Do you really think you can survive without it?”

Dartington Trust Contacts to write to:

Robert Fedder (Interim CEO): robert.fedder@dartington.org

Nick Harris (COO): nick.harris@dartington.org

The Dartington Trustees: trust@dartington.org (these are listed on the Charity Commission website)

We’ve created a Save the Dartington Forest Garden page about this is at www.agroforestry.co.uk/save-dartington-forest-garden where updates will be posted and your messages of support too if you want. Send messages of support to be posted there to SavetheFG@agroforestry.co.uk

Call for Economic Boycott of Dartington Hall Trust

Some local ART supporters are doubtful that DHT will pay any attention to these kinds of protests, and argue that since DHT only understands the value of money, economic actions need to take place to persuade them to change their minds – in effect an economic boycott. They want people to ask themselves: Do you really want to give your money to such an unethical organisation? If not then target DHT and not the many wonderful business tenants on the Estate:

· Don’t go and stay there.

· Don’t buy their food at the White Hart. (But the Green Table/Montrel bagels are run by tenants)

· Don’t use or rent their facilities.

· Don’t use the DHT Cider Press shops

· Watch films at Totnes cinema rather than the Barn at Dartington Hall

· If you’re a funder, think twice about funding DHT

· If you’re a tenant on the Estate – maybe look elsewhere when your lease is up. Otherwise watch your back.

· If you’re a prospective tenant – look elsewhere!

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Forest Gardens / Food Forests are overall more inherently resistant to extremes of weather due to their diversity in structure and species [No, I don’t have scientific proof of this, but it’s pretty darn obvious] than most growing systems based on a monocultural mindset.

But can we design in more adaptive features for the future?

Instability heading our way

Readers of this blog will need little reminding of the climate change challenges we are already facing but in terms of plants and growing systems there are issues to address now and into the future:

• More summer droughts

• Need drought resistant plants especially on well drained soils

• May need more irrigation and water storage

• Designers and growers need data on drought tolerant plants and rootstocks

• Make soils more resilient by increasing organic matter levels using organic mulches, chop-and-drop etc.

Almonds are more drought tolerant on almond rootstocks

• More spells of intense heavy rain (especially in winter in Western Europe)

• Need good drainage as few plants of use to us can grow in very wet soils. Designers and growers need data of plants tolerant of temporary waterlogging

• Improving drainage can also increase drought stress though.

• Make soils more resilient by increasing organic matter levels.

Walnuts are tolerant of temporary waterlogging

More higher-intensity storms

• Windbreaks need designing better, thicker, denser

• More data about the windfirmness of windbreak species would be useful

Warmer growing seasons

• An opportunity to grow new crops (just this week The Guardian had a piece by the RHS on how almonds and figs are thriving in England)

• An opportunity to change varieties of existing crops that need a longer growing season.

Persimmons are doing well in England

Falling winter hours of cold / chill

• May need to change varieties to lower-chill

• May need to change species entirely if they don’t get chill they need

• More data on chilling requirements on different varieties would be useful

Ideological and practical requirements to grow more of our own food due to societal breakdown

• Replacement of staples a particular challenge in Food forests. Do we all just eat lots of nuts?

Heartnuts - an excellent part of a nut-based diet

A strategy to maximise diversity will also mean accepting that not all crops do well every year

• By maximising diversity we are not necessarily maximising yield.

• This may have implications on how FFs fit into the current unsustainable economic system.

We might to accept that with respect to our growing systems we will have to go through many of the same stages as with grief (not sure if Kubler-Ross intended her work to be applied to plants!):

• denial that climate change is damaging our systems

• anger that this is happening because of human inability to live in harmony with nature

• bargaining (“if only I’d taken more care of that tree….”)

• depression when you see favourite plants fail

• and acceptance that some plants will inevitably fail, but that we can design our systems to survive and thrive overall (hopefully).

Within a few decades there are even larger issues to confront:

• In Western Europe, failure of AMOC (Atlantic meridional overturning circulation later this century may lead to a steady cooling of 3-7 C in Europe which could lead to cold hardiness and season length issues. In Britain a 3 or 4 C drop that would be like the climate of northern Scotland transferring to Southern England. So far any reduction in AMOC has been outweighed by global heating; this may continue or not ….

• The risk of fast changes in climate due to earth system tipping points being passed will increase steadily over the next decades. If this happens then there could be rapid increase in temperatures which will cause agricultural chaos.

How do we address these conflicting uncertainties? It seems to me that we cannot address these last two points as there are so many unknowns. But if we can address the earlier ones that should put us in a good place whatever happens.

The bayberries (or wax myrtles) are deciduous and evergreen shrubs, and belong to the group of actinorhizal plants, that is temperate region plants which form associations with Frankia species of fungi in root nodules, which fix atmospheric nitrogen for the plant.

Leaves are alternate and often with resin glands, shaped like and resembling in aroma Mediterranean bay leaves (ie from Laurus nobilis); flowers are inconspicuous, without sepals and petals, in small dense catkins. All species are dioecious to a large extent (though not 100%), ie male and female flowers usually form on different plants. The fruit is a small round drupe, often with a waxy coating.

Although different species have some similar and some different uses, it should be borne in mind that these species are fairly similar and contain many of the same substances, hence all are likely (for example) to have medicinal uses etc.

Myrica californica

Cultivation

Most species prefer an open position in sun or partial shade (all grow well in the understorey of forests including conifer forests), and an acid or neutral well-drained soil. M.cerifera and M.californica prefer moist soils, and M.gale is well adapted to boggy sites. The evergreen species tolerate considerable shade. All tolerate strong winds and are suitable for using in windbreaks.

Plants of some species are fairly easy to grow from seed. The seeds have a coating of wax which must be removed before sowing - either gently rub the seeds between sheets of sandpaper, or soak them in hot water to melt the wax. Layering can also be used to propagate all species.

Root cuttings are the best way to propagate M.gale. Seed germination is unreliable for this specie, but can be encouraged by floating seeds on water at 5°C for several weeks, then sowing them in the light.

Young plants in the nursery may naturally become inoculated with Frankia species, and if they do then nodules will be seen on the roots. Plants can also be inoculated on planting by mixing a little soil from an established stand of the species or a relative in the planting hole.

All species are very tolerant of pruning and trimming.

Common uses for all species

• The wax which coats the small fruits of all species has been used mainly to make candles which are quite brittle, aromatic and don’t smoke when put out. Other uses for the wax include soaps, ointments, leather-polishes, etching, and medicinal mixtures. One litre of M.cerifera fruit yields 50 g of wax; the wax melts at 47-49°C (116-120°F), so is easily melted off fruits in hot water, and skimmed off the surface. It is harder and more brittle than beeswax.

• Bee plants. The flowers of all species are attractive to bees.

• Hedging. All species tolerate wind and maritime exposure, and can be used for an informal hedge.

• All are green manure plants, increasing the amounts of Nitrogen in the soil and making available significant amounts to other nearby plants. M.cerifera has been recorded as accumulating 120 Kg/Ha of nitrogen per year, making it one of the best temperate nitrogen-fixing shrubs. Dense stands of M.gale are estimated to fix at least 30 Kg/Ha/year. M.pensylvanica has been recorded as accumulating 16-32 Kg/Ha/year just from leaf litter; root turnover probably doubles this.

• Leaves of all species can be used as a spice / condiment.  They have a bay-like aroma.

Warning note: There is a report that some of the constituents of the wax may be carcinogenic, hence using the whole fruits in cooking (as a condiment) may not be advisable, although in small quantities there is probably little risk; the wax might also melt and mostly run off the cooked food, eg. roasted meat. Also, there are reports of M.gale having an abortifacient action; pregnant women should avoid taking any plant parts of any of these species internally.

M.californica

Californian bayberry, Californian wax myrtle. Found from California to Washington in the western USA.

Upright evergreen shrub, usually growing 2.5 m (8 ft) high, occasionally to 4-10 m (13-33 ft) high. Leaves are 5-10 cm (2-4”) long, dark green and glossy above, smooth or pubescent beneath; not as strongly scented as the other species. Catkins about 25 mm (1”) long in May-June; usually monoecious (both sexes on the same plant). Fruits are 4-6 mm (0.2”) across, deep purple with a white waxy coat. Hardy to zone 7 (-15°C) and hardy in most of Britain. Tolerates very acid and wet soils.

• Grey-brown and marron-purple dyes are obtained from the fruits, fresh or dried.

• The wood is heavy, very hard, strong, brittle, close grained.

• The bark and leaves have historically been used on occasion for gastrointestinal ailments. The most active chemical is apparently the glycoside myricinic acid.

Fruits of M. californica

M.cerifera 

Bayberry, Wax myrtle. SE North America, possibly naturalised in S.England.

Evergreen slender upright shrub or small tree, growing to 9-12 m (30-40 ft) high. Leaves are 3-7.5 cm (103”) long, deep green above, lighter below, both sides with tiny golden-yellow resin glands. Flowers in March-April; fruits are 2-3 mm across, greyish-white, waxy, in clusters of 2-6, and can hang on the plant for several years. Hardy to zone 6 (-20°C). ‘Myda’ is a large-fruited female form of low growth.

M.cerifera leaves

• Leaves and fruits are added to foods, eg soups, as a condiment (an agreeable bay substitute) (see note above). Leaves are also steeped to make a tea.

• Leaves show some antimalarial activity. They also repel fleas and moths.

• The bark, leaves and roots have all been used medicinally (the root bark was the ‘official’ drug, containing the triterpenes taraxerol, taraxerone and myricadiol). Being bitter and astringent, it stimulates the circulation, increases perspiration, and is antibacterial. It is still used for colds, flu, coughs and sore throats, irritable bowel syndrome, colitis, vaginal discharges, ulcers and sores.

• The root bark is used as a commercial flavour ingredient in some soft drinks in the UK.

• A blue dye is obtained from the fruits.

M.gale

Sweet gale, Bog myrtle. Northern temperate regions.

A common medium sized deciduous upright shrub, growing to 2.5 m (8 ft) high, but sometimes (from grazing pressure or poor sites) only to 50 cm (20”) or less. It spreads by rhizomes to produce thickets. Leaves 3-5 cm (1-2”) long, deep green and smooth above, somewhat pubescent beneath.

Although mostly dioecious, sometimes male and female flowers are formed on the same plant or even the same branch; flowers are brownish, cone-like catkins, 1.5 cm (0.6”) long in April-June, the females thicker than the males. Fruits are to 3 mm across, yellowish-brown.

Extremely hardy, to zone 1 (-45°C). Usually found on wet acid soils, also on neutral soils. The most striking feature of the plant is the pleasant smell of the volatile oil which is secreted from numerous glands on its leaves and catkins. The scent  resembles that of sage, but is more camphoraceous. It is readily grazed by hares and goats, also by sheep, cattle and deer.

Myrica gale

Sweet gale is a dominant species in several plant associations on open peatland, apparently growing best on ground strongly irrigated with mineral-rich water. It may thrive and achieve dominance on less fertile soils primarily because of its symbiotic association with nitrogen-fixing Frankia species in root nodules attached to the plant. Dense stands of M.gale are capable of fixing substantial amounts of nitrogen - 30 Kg/Ha/year has been estimated. It will also accept infection by many different Frankia strains from different species, including alders (Alnus), Elaeagnus, and sea buckthorn (Hippophae rhamnoides).

Though it grows in areas where water is close to the surface in summer and frequently flooded in winter, there is evidence that plant growth is in fact greatest in wet but well-aerated soil - plant growth is less on very wet soils and the dominance of sweet gale on such soils reflects superior tolerance rather than preference. Haemoglobin occurs in high concentrations in the root nodules of this species, which may be an adaption to growth in wet soils.

Catkins open in April or May and nodule activity begins in late May / early June when soil temperatures reach 8°C and leaves are beginning to unfold. New shoots grow from buds on the previous year’s woody stems and later in the season, from new aerial shoots arising from rhizomes. Leaf ageing and loss begins as shoots reach their final length and continues slowly through the summer while the same shoots are developing new leaves. During September or October, leaf production stops and leaf loss accelerates, leaving branches bare by November. At this stage, fruits are mature, nodule activity has ceased and the soil has been enriched by substantial amounts of leaf litter (which could benefit nearby trees, for example.)

The shrub has been harvested from the wild and utilised in various ways for centuries:

• The most widespread use in the past has been for flavouring beer. Evidence stretches from Roman and Viking sites for its use in brewing as a flavouring and preserving agent. ‘Gale beer’ in Yorkshire was considered very efficacious for slaking thirst. It is also used to flavour mead. The beer-preserving activity of M.gale is at least partly explained by the discovery of antibacterial flavonoids which are particularly active against gram-positive bacteria; these act in a similar way to the bitter compounds humulone and lupulone obtained from hops. The use of sweet gale in commercial beer making fell into disrepute 250 years ago because excessive consumption was believed to cause poisoning; but the present widespread consumption of M.gale flavoured drinks in Scandinavia (see below) is evidence against any severe toxic effects at the doses normally consumed.

• In Scandinavia, leaves are still gathered to flavour alcoholic drinks: in Denmark, Aalborg Pors Snaps is flavoured with an extract made by soaking freshly picked leaves in 35% aqueous alcohol; in Norway, dried and powdered leaves are sold to the public for flavouring spirits and home made beer.

• Other food uses still practised in Newfoundland include a tea made from the leaves; and the fruits are used as a condiment to season roast meat (see note above). the leaves have also been used as a food flavouring.  

• The roots have been used to produce a yellow dye for wool - used in the Scottish Highlands within the last 80 years. The stem tips also yield a yellow dye.

• The cultivar ‘Nanas’ is spreading and makes a good ground cover; it is very shade tolerant.

• Leaves yield a flavonoid and a volatile oil with antifungal activity against several species including Fusarium spp and Penicillium citrinum.

• There is plentiful historical evidence of the use of sweet gale as an insect (moth) and flea repellent in Scandinavian and British folklore, though the volatioil was never produced for this purpose. A strong decoction of the leaves can be used as a parasiticide to kill external body parasites (lice).

• The foliage has been used to repel midges in Scotland. Large scale production of M.gale is being considered after recent research on the Isle of Skye in Scotland demonstrated that the steam distilled volatile oil is an effective insect repellent (a 0.5% gel preparation of the oil repelled biting midges [Culicoides impunctatus] for up to 3 hours). The oil has also been shown to repel ants.

• The volatile oil is produced on catkins and fruits, as well as leaves, but the former are unlikely to  provide significant yield as they never exceed 0.73% of total dry weight. Following these experiments, a range of Myrica-based products is under development in the UK for which the source of oil is leaves harvested by hand in the Scottish highlands. Wild collection, although sustainable and allowing regrowth, is labour-intensive and unlikely to supply enough material if products are successful. Sustainable production depends on adequate regrowth after cutting - both wild and plantation sites are likely to suffer if too many leaves/twigs are harvested too rapidly.

• Sweet gale has the potential to become a valuable crop on land of low agricultural value.

• Recent pharmacological studies have focused on myrigalone B (MyB), a flavonoid extracted from the fruits. MyB is a potent antioxidant which may help to protect liver tissue from toxin-induced injury, and act as a preventative to atherosclerosis. A fresh extract of plant material in water has also demonstrated antiviral activity, which supports the Scandinavian folkloric use of M.gale extract to treat Herpes zoster.

Male catkins of bog myrtle  (source: Sten/Wikimedia)

Female flowers of bog myrtle (source: Hajotthu / Wikimedia)

M.heterophylla

Bayberry. Eastern N.America.

Very similar to M.cerifera; an evergreen shrub normally growing 3 m (10 ft) high, but occasionally a small tree to 12 m (40 ft) high. Leaves 4-7 cm (1½-3”) long, rounded at the apex. Fruits greyish-white, 3 mm across, with a heavy waxy coat. Hardy to zone 6 (-20°C). Has the same uses as M.cerifera.

M.pensylvanica

Northern bayberry. Eastern N.America, poss. naturalised in S.England.

Deciduous or semi-evergreen dense shrub to 2-3 m (6-10 ft) high. Tolerates very acid, saline and light sandy soils. Leaves 4-10 cm (1½-4”) long, pubescent on both sides, with glands beneath. Fruits are to 4 mm across, greyish-white, waxy, and persist long into winter. Very hardy, to zone 2 (-40°C). Closely related to M.cerifera, it may be a hardier northern form of it.

• Leaves and fruits used in cooking as a condiment (see note above).

• Leaves and root bark have been used medicinally.

• A green dye is obtained from the leaves.

• Widely used for erosion control in N.America.

• Bayberry essential oil, extracted from the aromatic leaves, is used to scent many products. It has a high eugenol content.

Myrica pensylvanica

Fruits of Northern bayberry

Myrica rubra

Red bayberry. Southern China and probably other parts of SE Asia.

Red bayberry, also called Chinese tree berry, Yangmei, Chinese strawberry tree, Chinese Bayberry, Japanese Bayberry,  Zhuhong, Zhuroing, Shanyangmei, Shumei (in Taiwan) or yamamomo (in Japan).  It is an important fruit and forest tree in China, with large and increasing areas cultivated (over 230,000 ha in 2003) to supply a large demand for the fruits.  As well as an important economic tree there, it has great ecological and social value too.

Myrica rubra (Syn. M.nagi) is a stone fruit with a  berry-like edible portion comprising fleshy segments.  The rich red colours and appealing flavour make this juicy fruit very popular with Chinese consumers.

Commercial cultivation of red bayberry has so far been mainly restricted to China, where most of the literature about it has been published.  Nevertheless there is great potential for growing it in other mild temperate and subtropical regions.

Red bayberry fruits (Photo courtesy of Zeping Yang

http://www.flickr.com/photos/zeping/)

Red bayberry is a cold tolerant evergreen fruit tree which can tolerate minimum winter temperatures of -9°C and grows and fruits well in temperate and subtropical zones with average annual temperatures of 14°C or more.  The species prefers a warm and humid climate with moderate to high rainfall (1000 mm annually).

It grows as a small to medium sized tree, often 5-10 m high in the wild in China and Japan, with smooth  bark (yellowish-green in young trees to grey-brown in mature trees) and a symmetrical rounded crown.  Branches are brittle and easily broken.

Fruits are usually deep reddish to dark purple (occasionally white, pink or black), flattish round, in cultivated varieties about 25-30 mm wide and little less long (or high), with a waxy coat.  They have a knobbly surface and look similar (though a little larger) to the fruits of the strawberry tree (Arbutus unedo) – hence one of the commercial fruit names, ‘Chinese arbutus’.  At the centre of the fruit is a single seed, about 8 mm in diameter (similar in size to a cherry stone).

In China, there are over 300 cultivars, most derived from chance seedlings, and most of which have been evaluated on agronomic characteristics and quality. 

The fruits of red bayberry are nutritious, succulent and aromatic, the flesh being juicy with a rich colour and an agreeable sub-acid (sweet-tart) taste resembling strawberry and cranberry. 

In China, many fruits are pressed to make juice which can be stored for longer or fermented. 

Due to its long lifespan, great economic value, low production costs and nitrogen-fixing ability, red bayberry is regarded as a “money making tree” and has been an important  economic source for people living in mountainous regions of China.  There, people prefer red bayberry to citrus, and beautiful packages of fresh fruits are used as precious gifts.  It has a strong social value in the life of Chinese people.

Apart from use as a fresh fruit, various products are made including juice (like a sweeter cranberry juice; available commercially outside of China where it is being marketed as bayberry juice and ‘yumberry’ juice), jam, fermented alcoholic beverages, brandy (soaked in the Chinese liquor ‘baijiu’), wine, candies, canned fruit, salted fruit and dried fruit.  It has an edible seed with 40% oil content of the kernel; the seed can be roasted or used for extraction of oils.

A water-soluble red pigment is extracted from the fruits and used as a food colouring.

Other uses of M. rubra include:

• The fruit, seed, bark, leaf and root of red bayberry are important components of traditional Chinese herbal medicine.  The fruit and leaf are used for treating congestion, coughs, digestive problems and diarrhoea; the bark is used for skin diseases, wounds and ulcers.  The seed kernels contain vitamin B₁₇ which can apparently inhibit or kill cancer cells.  In recent years, a number of pharmaceutically active compounds (flavonoids and polyphenols) have been identified from different parts of the plants.

• Soil conservation and regeneration  Red bayberry has extensive adaptability along with a nitrogen-fixing ability.  It is regarded as a “fertiliser generating tree” and widely used on poor soils and for soil conservation and reclamation projects, and to improve the organic matter content of soils.  It also has good fire resistance and is tolerant of heavy metal soil contamination.  It is often interplanted with forestry trees such as pines as a beneficial interplant; also as firebreak strips as the they are resistant to burning.  Up to 460 kg/ha of nitrogen can be fixed.

• Amenity  Red bayberry is a tall shapely tree which is resistant to pests and disease damage and tolerant of air pollution.  It is used as an ornamental tree in parks and along roadsides.  However, trees can make a mess of public streets when they drop fruit!

• Leaves and branches are used in floristry, especially in winter.

• The bark contains abundant tannin (10-27%) which is used as a dyeing material for dyeing cloth yellow and brown.

Liquorice (‘licorice’ in North American English) has a long history of use as a herb and was valued for giving vitality, and longevity, and as a beautifying agent and aphrodisiac. It was seen by many as an 'elixir of life' and its use appears to have been almost universal. It was used in Chinese herbal medicines dating back 5000 years and is also recorded as being used in Mesopotamia, ancient Egypt , the Roman Empire, by the Ancient Hindus and by early Buddhists.

The Liquorice of medicine and commerce is derived from the sweet root of various species of Glycyrrhiza, a genus which contains about fourteen species, natives of warmer temperate countries in both the New and Old Worlds, ten of them having roots more or less sweet, but most of them not sufficiently so to be of use.  They are legumes, nitrogen-fixing plants which like sun and a well drained site.

The use of the Liquorice plant was first learnt by the Greeks from the Scythians. Theophrastus (third century B.C.), in commenting on the taste of different roots , instances the sweet Scythian root which grows in the neighbourhood of the Lake Maeotis (Sea of Azov), and is good for asthma, dry cough and all pectoral diseases.

Dioscorides, who names the plant Glyrrhiza (Greek glukos, sweet, and riza, a root), from his description of the plant possibly had in view G.echinata, as well as G.glabra.

Currently it is grown commercially mainly in Spain and France, also the Middle East and Asia. In the early 16th Century, liquorice began to be cultivated in the monastery garden at Pontefract, England and this later became the centre of the liquorice confectionery industry.

Description

Glycyrrhiza  plants herbaceous perennials with light, spreading, pinnate foliage, presenting an almost feathery appearance from a distance. The leaflets (like those of the False Acacia) hang down during the night on each side of the midrib, though they do not meet beneath it. From the axils of the leaves spring racemes or spikes of small pale-blue, violet, yellowish-white or purplish flowers, followed by small pods somewhat resembling a partly-grown peapod in form.

The root system has two parts, one consisting of a vertical or tap root, often with several branches penetrating to a depth of 90-120 cm (3-4 ft), the other of horizontal rhizomes, or stolons, thrown off from the root below the surface of the ground, which can grow a few metres / several ft. These runners are furnished with buds and throw up stems in their second year. The perennial downward-running roots as well as the long horizontal stolons are equally preserved for use.

In the wild, liquorice is found on sandy soil near streams, usually not being  more than 50 yards from water.

The flavour of liquorice comes mainly from a sweet substance called anethole, which is also found in other plants (notably sweet cicily, Myrrhis odorata). Much of the sweetness in liquorice comes from glycyrrhizin, a compound 30 to 50 times as sweet as sucrose.

G.echinata

A native of Hungary, Italy, south Russia and Asia Minor, this grows about 1m high and has short globular heads of flowers and a small, ovoid pod with long spines. The root is also somewhat bitter and in the past it been confused with G.glabra glandulifera. Photo in flower above.

G.glabra – true/Spanish liqourice

This grows about 1m high, the pinnate leaves have 9-17 leaflets.  Flowers are purple to pale blue. In G.glabra, the pods (2.5cm / 1” long) are smooth, hence the specific name; in others they are hairy or spiny. The pods contain 1-7 small dark kidney shaped seeds about 2mm across. The development of 'runners' or horizontal stolons indicates that the root system has developed to the stage where it can be harvested.

G.glabra glandulifera – Russian liquorice

In the subspecies glandulifera (sometimes included as a separate species G.glandulifera) which grows a similar height to G.glabra, the pods are covered with thick, glandular spines, and the whole plant is pubescent or roughly glandular. The underground portion is not so spreading and produces a carrot-shaped root larger than the Spanish root derived from G.glabra. This species is indigenous to South-east Europe, Syria and Western Asia, and is both wild and cultivated in Russia. Both the Russian and Persian Liquorice of commerce is derived from G. glandulifera, the Russian is sold peeled or unpeeled: its taste although sweet, is accompanied by a more or less perceptible bitterness. It consists chiefly of roots, not runners.

Persian Liquorice root, from Iraq and Iran, is usually unpeeled, and is in rather large, coarse pieces, closely resembling the Russian root.

G.lepidota – American liquorice

This is a species of the north-western United States growing about 1m high. The rhizome resembles that of Spanish Liquorice, but is thinner. It has a long history of edible and medicinal use by the native American peoples.

G. lepidota

G.uralensis – Chinese liquorice

Originates from Turkestan, Mongolia and Siberia, similar in quality to  Russian Liquorice. Widely used in China. Widely used in Chinese medicine as well as traditional medicines of many other Asiatic coutries. Grows to 1.5m (5 ft) high.

Roots are collected spring and autumn, and often sun dried.

Cultivation

Liquorice requires a well drained (though preferably still moist) soil and full sun.

Owing to the depth to which the root penetrates and its ready propagation from detached pieces, the plant is a most persistent weed in cultivated grounds where it is indigenous and almost impossible to get rid of.

It is very healthy and robust, not susceptible to any pests or diseases.  Plants also appear to have an allelopathic effect, suppressing the growth of other plants nearby.

Commercial propagation is by seed or by cuttings from the stolons (runners).

The seed has a hard seed coat and needs to be scarified prior to sowing. Germination and early seedling growth is often slow so propagation from root cuttings is preferred.

Root cuttings 20-40 cm long with buds are used and these can be planted vertically into the soil in the dormant season, about 10cm deep. 

Grown commercially, the plantation is established with root cuttings in the early spring or late summer/early autumn with 30 cm between plants and 60 cm between rows. The land is worked deeply to provide a friable seedbed which will favour root growth. The plants make limited growth for the first two years, growing only to a height of 30 to 50 cm. Because of this slow growth, commercial growers often plant quick-growing vegetable crops between the rows of liquorice during the first two years.

The crop is ready for harvesting in the autumn of the third or (usually) fourth year. The usual practice is to carefully remove the soil between the rows, exposing the roots and runners at the sides, digging to a depth of 60+ cm (!). The whole plants are then removed and the soil placed in the trench. The roots are then washed and cut into lengths 30 to 60 cm long, sorted and graded. For commercial production, the root is sold fresh but for home use the roots can be air dried or dried artificially at a temperature of 30 to 40C. Commercial yields of fresh root machine-harvested range from 1 to 5 tonnes per hectare; formerly liquorice was habd dug to a greater depth and yields could be double this.

Fresh Liquorice when washed is externally bright yellowish brown. It is very flexible, easily cut with a knife, exhibiting a light-yellow, juicy internal substance, which consists of a thick bark surrounding a woody column. Both bark and wood are extremely tough, readily tearing into long, fibrous strings. The root has a peculiar earthy odour and a strong, characteristic, sweet taste.

Russian Liquorice grows to a larger size than the Spanish, and the taste, although sweet, is accompanied by a more or less perceptible but not strong bitterness or acridity. It consists chiefly of roots, not runners, in long often crooked pieces, about 2 inches in thickness, pale yellow externally and internally of a lighter yellow than the Spanish and softer.

Commercially, the liquorice extract is produced by fine-cutting the roots or crushing them to produce a pulp. The crushed or cut material is then boiled with water and the extract evaporated to produce either a liquid or solid form. The latter is rolled into sticks 2-3 cm in diameter and 15 cm long known as Hard Extract of Liquorice. Unfortunately, much of the liquorice sold today as strap or yard long liquorice is not pure liquorice but a processed lolly which contains other ingredients such as molasses, treacle and aniseed.

Uses

The chief constituent of true liquorice root, to which its sweet taste is due (and which has medicinal properties) is Glycyrrhizin (6 to 8 per cent), obtainable in the form of a sweet, white crystalline powder, consisting of the calcium and potassium salts of glycyrrhizic acid. Also present are sugar, starch (29 per cent), gum, protein, fat (0.8 per cent), resin, asparagin (2 to 4 per cent), a trace of tannin in the outer bark of the root, yellow colouring matter, and 0.03% of volatile oil.

The roots of G. Glabra glandulifera and G.echinata also contain in addition, glycyrmarin, a bitter compund occurring mostly in the bark.

Edible uses

Liquorice flavour is found in a wide variety of liquorice candies or sweets. In Britain and the US these are usually sweet. In most of these candies the taste is reinforced by aniseed oil, and the actual content of liquorice is very low. In continental Europe however, strong, salty candies are popular.

In the Netherlands, where liquorice candy ("drop") is one of the most popular forms of sweet, only a few of the many forms that are sold contain aniseed, although mixing it with mint, menthol or with laurel is quite popular. Mixing it with ammonium chloride is also popular, and is known as Salmiak, but mixing it with table salt creates what is probably the most popular liquorice, known in the Netherlands aszoute drop.

Pontefract in Yorkshire (UK) was the first place where liquorice mixed with sugar began to be used as a sweet in the same way it is in the modern day. Pontefract Cakes (which are more like lozenges) were originally made there.

Liquorice flavouring is also used in soft drinks, and in some herbal infusions where it provides a sweet aftertaste. The flavour is common in medicines to disguise unpleasant flavours.

Liquorice is popular in Italy (particularly in the South) and Spain in its natural form. The root of the plant is simply dug up, washed and chewed as a mouth freshener. Sticks of liquorice typically have a diameter between two and ten millimetres. Although they resemble plain wooden sticks, they are soft enough to be chewed on. These were also popular with European children in the 1950’s and 1960’s.

Throughout Italy unsweetened liquorice is consumed in the form of small black pieces made only from 100% pure liquorice extract; the taste is bitter and intense. In Calabria a popular liqueur is made from pure liquorice extract. Liquorice is also very popular in Egypt and Syria where it is sold as a drink.

Chinese cuisine uses liquorice as a culinary spice for savoury foods. It is often employed to flavour broths and foods simmered in soy sauce.

G. uralensis

Medicinal uses

Liquorice is widely used around the world as a herbal medicine. The list of complaints for which liquorice is claimed to be effective is so extensive that it appears to be a universal panacea. There are some medical conditions which are aggravated by liquorice but for normal healthy adults there is no real risk in using liquorice in moderation and its healing benefits far outweigh the risks.

The compound glycyrrhizic acid throughout Japan for the treatment and control of chronic viral hepatitis. Recent studies indicate that glycyrrhizic acid disrupts latent Kaposi’s sarcoma (as also demonstrated with other herpesvirus infections in the active stage), exhibiting a strong anti-viral effect. In China liquorice is used to treat Tuberculosis. In traditional Chinese medicine liquorice is considered an adaptogen and is commonly used in herbal formulae to relieve a spasmodic cough.

Liquorice affects the body’s endocrine system as it contains isoflavones (phytoestrogens). It might lower the amount of serum testosterone slightly, but whether it affects the amount of free testosterone is unclear.

Side effects

Moderate consumption of liquorice is not harmful.

Liquorice root contains glycyrrhizin, which can cause high blood pressure, salt and water retention, and low potassium levels; it could also lead to heart problems. Patients who take liquorice with diuretics or medicines that reduce the body’s potassium levels could induce even lower potassium levels. Taking large amounts of liquorice root could also affect cortisol (a body level’s hormone) levels as well. People with heart disease or high blood pressure and the pregnant should be cautious about taking liquorice root.

Other uses

All liquorice species are excellent bee and butterfly plants, flowering June to August.

They are all also nitrogen fixing plants.

Here are the main early spring salad ingredients we’ve been using over the last 6 weeks in our mostly daily salads (this is not definitive, there are many other possible plants!)

Achillea ageratum – English mace

Alliums

                A. altaicum – Altai leek

                A. ledebournianum

                A. moly – golden garlic

                A. neapolitanum – Neapolitan garlic. Leaves and flowers

                A. schoenoprasum – chives. Leaves and flowers

A. ursinum – ramsons. Leaves and flowers

Golden garlic

Aquilegia vulgaris – columbine

Borago officinalis – borage. Flowers from the glasshouse.

Claytonia sibirica – siberian purslane. Leaves, stems, flowers

Crambe cordifolia  - seakale. Young leaves and the fabulous flowers.

Seakale

Fagus sylvatica - beech

Houttounia cordata – fish mint. Leaves are a favourite of ours.

Lepidium sativum  - cress

Melissa officinalis ‘Lemona’ – lemon balm. An extra lemony variety.

Mentha suaveolens – Apple mint

Myrrhis odorata - sweet cicily. Leaves early on, green fruits in last 2 weeks

Sweet cicily

Oregano vulgare ‘Greek’ – Greek oregano

Phyllostachys spp. – bamboo shoots, cooked and cooled

Plantago lanceolata - ribwort plantain

Rumex spp (sorrel/dock family)

                R. acetosa – garden sorrel

                R. patienta – monk’s rhubarb

                R, scutatus – buckler-leaf sorrel

Sedum sarmentosum – gold moss stonecrop. The best edible Sedum we’ve tasted so far! (yes we’ll have plants to sell in the autumn….)

Stellaria graminea – lesser stichwort. Leaves and flowers

Lesser stichwort

Toona sinensis  - toon

Tropaeolum majus – nasturtium. Leaves and flowers from the glasshouse.

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Leaves from grape vines (Vitis vinifera) have long been used in Mediterranean cookery eg. in Dolmas (Greece), Koupepia (Cyprus), Warek Enab (Lebanon), Yebreh (Israel) etc. These recipes all use vine leaves as wrapping for parcels of other food. More recently they are sometimes used in sauces and grape leaf pickles (often after being blanched and brined).

The great nutritional content of vine leaves was highlighted by a recent paper on perennial vegetables (1), where in a comparison with several hundred other perennial vegetables, vine leaves proved very high in fibre, calcium, iron, magnesium, zinc and vitamin A.

Vine leaves are incredible easy to grow, as anyone who has a grape vine will know, so I first tried stir frying young vine leaves as a vegetable, using leaves from the Phoenix vine in my back garden. Result: they were excellent, with a good texture and tangy flavour. But would there be much variation between different grape cultivars?

Method

Leaves of 27 different vine cultivars from our collection were picked in early morning in early August. Only young leaves were picked near the shoot tips of the growing shoots. One of the great things about grape vines is that they continue producing young leaves from spring right through most of the summer.

For each cultivar, the leaves were roughly chopped into approximately 2cm strips, then they were stir fried in a hot pan with a little olive oil for about 1 minute until cooked.

The leaves were then tested by a panel of tasters, concentrating on flavour and texture, and scored out of 10.

Results

It was obvious there were going to be large differences, particularly between pure Vitis vinifera cultivars and the Vitis hybrids. Most of the hybrid cultivars have clearly thicker leaves, often with a woolly layer on the inside of the leaf, whereas the vinifera cultivars have waxy thinner leaves with no woolly layer.

Leaves of Chardonnay (pure V.vinifera). Thin, waxy grape leaves like this are almost always good to eat as a vegetable.

Leaves of Seyval Blanc, clearly showing woolly backs. This variety is 50% Vitis vinifera; 37% Vitis rupestris; 13% Vitis licencumii.

After cooking, most of the leaves from the hybrids were chewy, sometimes pleasantly so, but sometimes tough enough to be practically inedible. The pure vinifera leaves were mostly very tender and good quality.

Leaf scores and comments

Grape cultivars recommended for leaf cultivation

The top scoring cultivars from above are listed below. It is worth noting that the tasters went back to taste the best 6 cultivars at the end and rated the top two as Precoce Noir and Chardonnay.

Conclusions

Most of the pure V.vinifera leaves in our collection were tender, with a good tangy flavour, often described as lemony. Many of the hybrid vine cultivars had leaves which were tough or chewy and this poor texture often outweighed any good flavour profile. It could be that the toughness of texture is related to the proportion of non-vinifera species in the parentage, especially V.rupestris, which varies a lot.

The hybrid vine cultivars were mostly developed because of the resistance they have to vine phylloxera. This American vine pest was introduced into Europe and became a serious problem in the late 1800’s. Hybrids involving American vine species (V.aestivalis, V.rupestris and V.riparia) had some resistance but the quality of grapes was never considered as good as those from pure V.vinifera. The hybrids turned out to be much hardier with respect to climate and other vine diseases, so are still valued where vinifera grapes are still somewhat borderline.

However, for leaf production, pure vinifera cultivars will grow very well even in harsh climates where they will not fruit. They can be managed similar to tree vegetables, cut right back every year or two to a permanent trunk. Vine leaves can make a substantial contribution to vegetable nutrition and are a highly recommended addition to perennial and forest gardens.

Thanks to our tasters – Caitlin, Eamonn and Ellen.

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Reference

1.     Toensmeier E, Ferguson R, Mehra M (2020) Perennial vegetables: A neglected resource for biodiversity, carbon sequestration, and nutrition. PLoS ONE 15(7): e0234611. https://doi.org/10.1371/journal.pone.0234611

A chat at work about brassicas being heavy feeders led me thinking ….

The whole of agriculture and horticulture has accepted without question that soils with high fertility are not only a good thing, but are one of the main things to aim for – in organic, biodynamic, regenerative and chemical-based systems.

Muck spreading in SW England

High fertility often leads to big yields of whatever crop you’re growing, so it must be good, right? Many annual, forage, shrub and tree crops only give the yields expected nowadays when there are excessive amounts of nitrogen and potassium applied to the soil. And the undervaluing (in the UK and many other countries) of food and the growers who produce it means that they feel the need to maximise yields.

So what’s the problem?

There are serious downsides to managing for high fertility. A major one is that excessive nitrogen applied to and circulating in the soil – whether applied as manures or chemical fertilisers – leads to lots of it escaping. Yes, some is taken up by the crop. But a lot – in the region of 80-87 % of chemical-based nitrogen, and 50% of manure-based nitrogen – is lost from the soil through a mix of washing out of the soil thereby polluting groundwater, and being lost into the atmosphere through oxidation into oxides of nitrogen. These latter compounds, as you probably know, are very powerful greenhouse gases – 290 times more powerful than carbon dioxide. This, more than anything, is what makes most high-fertility growing unsustainable in my view.

There are other downsides too. Plants respond to high fertility by putting on new growth with extra high nitrogen content, which attracts pests, and which is more susceptible to fungal diseases. So this leads to extra management needed for pest and disease control – extra chemicals used in most of agriculture.

The high nitrogen is also very detrimental to mycorrhizal fungi. These vital members of the soil community hate excessive nutrients and often fade away in their presence (they also hate compacted soils so become even rarer in chemical-based agriculture). Without them and the benefits they bring, the crop plants become even more vulnerable – to soil-borne pests, to drought and other stressful situations. And this leads to even more management interventions required – more chemicals, more irrigation.

Nematodes can cause root and crop damage but are controlled by mycorrhizal fungi

We need to remember that high fertility is a fairly rare and occasional event in nature, usually after a major event leading to a forest fire or a flood, where a pulse of high fertility is created by ashes, river silt etc. Ecologically this kick-starts natural succession with annuals as the first plants to recolonise bare soil. The annuals quickly use up the excess nutrients and then perennials take over in the lower-nutrient regime. Traditional swidden agroforestry emulated this by cutting down a small bit of forest, burning the woody material, then growing annuals for a few years followed by a food forest system: these systems in the topics were highly sustainable while the human population was low.

There is a tendency for organic and regenerative growers to believe that nitrogen from animal sources is less damaging to the environment, and to some degree they are right – at least the nitrogen from manures is not made in energy-intensive factories like chemical nitrogen fertilisers, and less of the nitrogen is wasted – only 50%(!) But that is still a lot of nitrogen potentially damaging the environment. Not to mention the methane from ruminants but that’s a whole other issue.

How much less nitrogen should there be in our growing systems? It’s difficult to give any sort of accurate figure. The problem for non-organic growers, especially arable growers, is that the soil has been damaged so much that it has no resilience left and without plentiful fertiliser crops can completely fail (although the cost of nitrogen fertilisers has risen hugely since the Ukraine war, encouraging farmers to cut down a bit.) As for animal-based agriculture, with livestock and their manures, it is instructive to look at the work of the renowned population biologist Prof. Vaclav Smil. His work shows that to stay within ecological carrying capacities there would need to be perhaps 10% or less of the livestock that there are now (and a lot fewer humans but that’s a whole other discussion.)

Graph showing mass of terrestrial vertebrate biomass and global carrying capacity (the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available.) Source: Smil (2011).

Some people will say: “we’ve got to maximise yields otherwise there won’t be enough food for everybody”. My response to that is that without a sustainable agriculture there is no future for a large portion of the human population; if the causes of climate change are not tackled in every area – including agriculture – then an even larger proportion of the human population is endangered.

By emulating natural ecosystems, food forests operate on a moderate fertility regime, though sometimes they are established starting with annuals in high-fertility and going through a succession process. Nitrogen-fixing plants in them are self-regulating, fixing less nitrogen when there is enough in the system already. This means that a healthy mycorrhizal layer supports and benefits all the plants within them. Drought resistance comes naturally. And the layered cropping system means that although the yields of individual crops may be less than those of a monoculture of that crop grown intensively, the total yields of the layered crops can compensate for the loss.

Perhaps we need to rethink our expectations of what are sustainable yields. It’s not easy, after being told that we should get x kg of crop with high-fertility growing, to accept that two thirds (or whatever) of that is just fine. But in a way it’s not different than accepting that we all need to reduce our high-consumption lifestyles and realise that having enough rather than always wanting more is essential to the future of human civilisation.

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Reference: Smil, V. 2011. Harvesting the Biosphere: The Human Impact. Population and Development Review 37(4) : 613–636.

http://vaclavsmil.com/wp-content/uploads/PDR37-4.Smil_.pgs613-636.pdf

• Where we are now

• The future for plants

• What should we do / what can we do

• Designing with ecological guilds

Where are we now

One of the ART’s original patrons was James Lovelock, originator of Gaia Theory: that life on earth interacts with their surroundings to form a self-regulating system that helps maintain conditions for life on the planet.

To show that this theory was not contradictory to the principles of natural selection, Jim developed the Daisyworld model as an example of a simple self-regulating system that regulates temperature (for a fuller explanation and interactive visual see https://www.islandsoforder.com/daisyworld.html)

A typical Daisyworld graph is below. You can see that the world with daisies has its temperature regulated over a wide range, whilst the world without has no such response. The point where the stresses of increased inputs cause the regulation system to fail (between 1.5 and 1.6 luminosity below) is called a tipping point.

The Daisyworld model was made more complex – showing, for example, that a more diverse collection of life forms leads to more stable climate regulation – but of course is nothing as complex as the earth itself.

What you can’t see in the graph above is that just before the tipping point, there is usually a big increase in variability – wobbles up and down from the smooth line.

For the earth there are numerous tipping elements in the climate system which also interact and may trigger each other in unknown ways. The unknowns are still huge, but it is becoming clearer that we are shockingly close to some of the tipping points and might already have crossed some of them.

One of the indications that we could be very near tipping points is the increasing variability of our weather. As climate change continues there are more weather extremes, and it is these that have a more significant effect on plants than gradually increasing global temperatures.

The future for plants

Plants in our growing systems and in the wild are going to experience increased instability, more weather extremes and more variability in year-to-year conditions, which is going to be very challenging.

In Britain and much of the world, climate zones are shifting Northwards at about 5Km per year. This is hundreds of times faster than after the last ice age. Some plants can move that quickly – think dandelion or willow seeds that can move tens of km on the wind. But many cannot – lots of trees take a few decades to flower and then have seeds that can only travel small distances.

If there were large contiguous areas of wild land then some species in the wild could move north with the shifting climate but many could not. And in Britain we don’t have that much wild land at all. This means that for a lot of our ‘native’ species they can’t move and therefore will have to try and adapt where they are. This too will be easier for some than others. Those that can’t move could die out – this is already starting to happen to English oaks in the Southeast of the country.

In addition, beneficial and pest insect/animal species are all adapting at different rates, some able to keep up with the shifting climate but many not.

For plants that we cultivate the challenges are just as great. Annuals and fast-flowering plants have the potential for fast seed adaption to new conditions, but if the variability in weather is inconsistent from year to year then what will they be trying to adapt to? For a lot of other perennial and woody plants, they could have greater problems in adapting.

What should we do / what can we do

For our wild/’native’ systems there are more questions than firm answers that people agree on. Should we introduce new species to take over as some – eg. English oak as above – die out? We can allow some species to naturally move north and colonise but only a few can move fast enough to do this. Do we accept degraded ecosystems or do we intervene? This relates to deeper questions about the role of Humans on this planet – I am not comfortable with the ‘humans as stewards’ attitude which has not worked well so far!

As for growing systems to feed the human population, this is what we are trying to show in the most ecologically sound way. In many ways it is based on giving to the land rather than taking from it.

One of the legacies of ten thousand years of agriculture and plant selection is the monoculture mindset, which is closely related to the commercialisation of agriculture. Modern economics – not so much a science as a materialistic scheme for wrecking the earth – has devalued agriculture to the extent that many feel forced down the monoculture route. In a shifting and erratic climate, monocultures are the very last thing we need.

The only way our growing systems might be able to cope in the future is by embracing diversity. Almost all the work on crop science has been on single crops, yet there is clear evidence that mixtures of plants, especially perennials, can be more productive, be better for soil, store more carbon, and be more resilient to climate and other stresses.

So how do we implement greater diversity in our growing systems to get resilience?

• Diversity of plant species

• Diversity of plant families (eg. apples, pears and plums are all in the Rosaceae so do not make a very resilient collection)

• Diversity of life spans reflecting nature - not too many annuals

• Diversity within species – more use of seedling plants, less use of cloned plants

• Embracing and allowing death of species to enable new opportunities

• Polycultures – intimate mixing of plants within systems

• Designing using ecological guilds (see below)

Basically, we want to try and recreate functioning ecosystems using plants more useful to Humans than found in most wild systems. In resilient agroecosystems we try and maximise the connections between the elements (plants, animals, insects, fungi etc) and using ecological guilds is one the best ways to do this.

Designing with ecological guilds

There is a lot of confusion over the use of the word ‘Guild’.

Originally used for groups of artisans engaged in a similar trade, ecologists have defined it in several ways, and Bill Mollison defined it in a different way for Permaculture systems.

Many people confuse guilds and polycultures. Polycultures are groups of species growing in the same patch. Sometimes polycultures are guilds but not always! Likewise, not all guilds are polycultures. Guilds often contain support species or system species.

Here I am using the guild definitions refined by Dave Jacke (forest garden designer and lead author of Edible Forest Gardens). These are clearer, more useful and more based on scientific ecology than Mollison’s definition.

Do I have to consciously use guilds?

You don’t. Plants can mixed more randomly, and if you use a large enough diversity then various guilds will emerge. And some of your normal planning will include guilds. But your system will not be as resilient compared with the one that will emerge through conscious use of guilds to some degree.

Defining guilds

Guilds are assemblages of species (which can include plants, animals/humans, insects, amphibians and others) that have a specific function or share a specific resource, and which generate a desired emergent property or outcome. There are three types, which are not mutually exclusive and can often overlap with species in both.

Resource Partitioning Guild (or Resource Sharing Guild) – RPG

The species in this guild partition or share a resource to avoid competition. The species in it are usually in the same ecological niche. Using a RPG will lead to reduced competition, increased biodiversity and increased productivity for individual guild members and the ecosystem as a whole.

Examples

A canopy layer forest garden design is an RPG sharing light

Mutual Support Guild - MSG

Here the yields of one species meet the needs of another in the guild. The species are not necessarily in the same ecological niche, nor in the same patch, in fact they can sometimes be a long way away (several miles).  “Support plants” or “System plants” often dominate MSGs. Apart from plants – birds, frogs, reptiles, insects, bacteria and fungi all offer functions that can support each other. Using a MSG reduces stress and work to maintain the system, increases stability of the system and reduces waste.

Examples

Comfrey (Symphytum officinale) with the nearby fruiting shrubs is an MSG with the comfrey providing potassium in particular.

Community Function Guild – CFG

This guild is based on species which share a community niche or function. The species can be of wide diversity and types from different niches but all basically doing the same job. A CFG provides redundancy and therefore stability of ecosystem function; increases diversity and ecosystem resilience. If species niches overlap too much, may cause competition. Ideally CFGs will also function as RPGs.

Examples

Good king henry (Chenopodium bonus-henricus) and wild strawberry (Fragaria vesca) form a Ground covering CFG

How to use guilds in food forests and forest gardens

Even if you do not consciously design using guilds, you will get some in your forest garden plantings. Some parts of forest garden design, for example designing the canopy layer or designing the ground cover layer, are basically designing a guild.

Polycultures are more effective if they are guilds.

However, the more guilds there are in your system, the more resilient and long-lived the system will be, and the less you will need to work to maintain it. So ideally try to design some of these guilds or add in plants over time to construct them. There is an almost infinite amount of time you could spend on designing guilds so you have to balance that against the time available and benefits gained (many of which are difficult or impossible to measure).

Some main outcomes for guild design

Outcome: Pest population balance

Outcome: Soil fertility maintainance/improvement

Outcome: Weed control

Outcome: Maximise productivity

I don’t seem to often get the chance to reflect on the previous year but today the chance has emerged (thanks Ciaran). With Rob Luft’s Dehab Days playing, reminding me of summer days when the whole ART crew would have leisurely lunchbreaks and even the occasional siesta, I remember what a lot I get from the rest of the crew – friendship, banter, lots of laughs (and some work too) – so thanks to Caitlin, Ellen, Fran, Holly and Sandra. With them we’ve expanded our food processing and experimentation too, and we’re hoping to work towards a new perennial foods cookbook in the near future.

The nut harvest this year was huge, and we celebrated by having our “Nutters lunch” with guest Mark Diacono. Nuts on the menu included acorns, bladdernuts, chestnuts, hazelnuts, walnuts and monkey puzzle nuts – not a bad selection!

I find that growing plants is the perfect antidote to the incessant bad news of the earth’s climate system starting to tip into chaos. How can growing new life not be at least a bit optimistic? In our nursery this year we’ve grown a wider range of plants than ever. Despite the recession/cost of living crisis, thankfully lots of people still believe it is good to invest in plants or seeds to help increase their food self-sufficiency. So thanks to all our customers which makes what we do possible.

We’re now into our winter season of despatching plants, and starting new plants from hardwood cuttings. These mostly go straight into the still-warm soil. The weather this year has been consistently inconsistent with a wet late winter, hot spring, autumnal summer, quite hot early autumn, and now a mild wet late autumn and early winter. Plants are confused - just like us - and most are still well in leaf, some deciding to risk a few more flowers. All the nuts and most fruits were 7-10 days early ripening. It is quite striking if you’re used to working with plants just how erratic the climate-plant system is becoming - and this is just the start of decades of increasing chaos. It is not a promising outlook and yet we have to remain positive, not by ignoring or denying the crisis (even via scientific conservatism), but by supporting each other and doing positive things in our own lives.

How we felt after the nuttters lunch ….

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