Tree of the month: June 2023 - Walnut

Our young Walnut Tree in full leaf at the Forest Garden, Parkwood Springs

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The Walnut is not a native tree. It was first introduced to Britain by the Romans, who valued it for its nuts. It is a fast-growing, hardy tree able to reach 35 metres in 60 years. When young the bark is smooth and deep olive/brown. As the tree ages the bark becomes fissured and gnarled. It takes around five years to start to bear nuts and from then the harvest will steadily increase.

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The Walnut, is encased in a wrinkled shell, growing inside a thick husk. It ripens mid-autumn and naturally falls to the ground, where mice, squirrels and other mammals eat it. Squirrels often spread the tree when they fail to retrieve all their caches of food. Don’t pick the husk until it opens to reveal the shell.

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The Wildlife Value of the Walnut Tree: It is not only the nuts that prove valuable to wildlife (they are eaten by Squirrels, Mice and other mammals)- the leaves are a food plant for moths, including many micro-moths. Around 1,850 species of our 2,500 moth species in the UK are micro-moths (having wing-spans less than 20mm). They are often hard to identify- there are whole books dedicated to these tiny moths. Moths are underrated in our ecosystems - they are invaluable pollinators for many cultivated crops and wild plants.

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Human Uses of Walnuts: Walnut Trees carry both male and female flowers. The wind carries the very fine pollen from the male flowers (catkins) to fertilise the female flowers. The Walnuts that result are very good for our health, and thought to help lower cholesterol. They can be eaten raw, roasted, salted or pickled. The ground nutshells are used as an abrasive.

The Oil can be used to make salad dressings and the sap is edible and sweet to taste. The oil has also been used as a wood polish, as a basis for varnish, used to burn in lamps and used in soap, shampoos etc.

Herbal uses have involved much of the plant. The leaves and bark are used as an astringent and detergent. The leaves can also be used as a hair-dye, for acne and to treat other skin conditions.

In the past the bark been used as a purgative and the shell used to treat blood poisoning. Juice was extracted from the husk of the nut and used as a throat gargle, as well as yielding a dark yellow dye.

The Walnut does produce a noxious substance called ‘juglone’ that is released into the soil and can affect other plants nearby, so it is often planted a little away from other plants. This chemical, present in much of the plant also led to its use as an insecticide. Fishermen are said to have used the bruised branches to stun fish.

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The deep green, glossy ‘pinnate’ leaves cast a dense shade, which also inhibits the growth of other plants under its boughs. When crushed, the leaves smell like polish. As it matures, the Walnut Tree makes a great specimen tree so they were widely planted in parks, the grounds of country houses and large gardens.

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Walnut timber: In the late 17th Century English Oak was overtaken by Walnut as the most sought-after timber for high quality furniture. It has a complex and fine-grain pattern and is a very stable wood. Walnut furniture can be seen in many of our old Country Houses but the fashion shifted as two thirds of the mature Walnut trees in Northern Europe were killed by a severe winter in 1709. By 1720 the French banned the export of Walnut, which was gradually replaced by Mahogany from Central America. Our furnituremaking ‘Friends’ member Robert tells us that Walnut is one of his favourite woods- most used now is American Black Walnut. European Walnut has varied heart and sap, and is dried with steam to lessen these differences. Sunlight, unlike for other woods, tends to lighten Walnut wood.

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Aesop’s Fable- The Walnut: ‘The Walnut Tree’ is one of Aesop’s Fables (620-564 BCE). A moral tale like many of these early fables, it expresses the idea of how cruelty and ingratitude can be shown towards those who do good- people gladly enjoy my fruits, it says, but they have a terrible way of showing their gratitude, throwing sticks and stones at me to bring down my walnuts. One translation recounts “O wretched me! That those whom I cheer with my fruit should repay me with these painful requitals!”

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Legends associated with the Walnut:
- The botanical name for Walnut, Juglans, is linked to the Roman myth of the god Jupiter who was said to favour eating Walnuts when he lived on Earth.

- An early Sanskrit legend tells of young men kicking the tree to make it flower so the tradition of beating Walnut tree trunks to make them fruit is clearly widespread and long practised - “the more you beat them, the better they be”. There is no truth to this long-practice - it is a myth. Through the ‘doctrine of signatures’, where plants that have the appearance of a body-part or disease were thought to be beneficial for healing that which they resemble, the Walnut, looking like a miniature brain, was thought to be good for brain-health. While there has been no direct link made in research, the fact that Walnuts are high in antioxidants, ‘good’ fats, minerals and vitamins means they are still regarded as good for general health.

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The famous American poet Mary Oliver wrote:
The Black Walnut Tree
“My mother and I debate we could sell the black walnut tree to the lumberman,
and pay off the mortgage….”
Two women trying in a difficult time to be wise.
She concludes to leave it as selling it would cause them shame “in the emptiness we’d made”

Random facts:
- Oxford University is trying to develop a Walnut Tree better suited to our climate.
- Turkey is a big walnut-producer but by far the biggest is California.