The walnut tree
The Wood Guide · The forests
The forest series · tree portraitThe walnut tree
Nuts in autumn and the most prized furniture wood in Europe. But don't plant anything under it, because this tree defends its spot chemically.
- Juglans regia
- Produces juglone
- Comes into leaf very late
The walnut tree in brief
The common walnut (Juglans regia), family Juglandaceae. Native from the Balkans to Central Asia, and planted in our region for millennia.
A walnut tree is rarely planted for its wood. It is there for the nuts, or as a solitary tree in a farmyard — and only when it is felled does it become clear how much the wood is worth. European walnut is one of the most expensive furniture woods there is.
And it has a trait few trees share: it releases juglone through its roots, leaves and husks. That substance inhibits the germination and growth of many other plants — a chemical way of keeping competition at bay, which botanists call allelopathy.
Tomatoes, potatoes, apples and many ornamental plants react badly to juglone and can wilt under a walnut tree for no obvious reason. Grasses, nettles and many bulbs are not bothered by it. If you are planting a vegetable garden, keep well away — the influence reaches roughly as far as the crown.
- Botanical
- Juglans regia
- Family
- Juglandaceae
- Origin
- Balkans to Central Asia, here for millennia
- Distinctive
- releases juglone — allelopathy
- Leafing out
- very late, often not until May
- Wood
- greyish brown with rich veining; highly sought after
To be fair: a walnut tree comes into leaf very late, often not until mid-May, and drops its leaves early. If you plant it for shade, you only have that shade for half the year. On top of that, the green husks leave a stubborn brown stain on patios and cars in autumn.
By the leaf and the smell
Pinnate leaves
Five to nine leaflets on one stalk, smooth and glossy. Rub one and you smell the characteristic, slightly bitter nutty scent.
Smooth grey bark
Silvery grey and smooth on young trees, deeply furrowed on older ones.
Green husks
The nut sits in a thick green husk that bursts open as it ripens. The juice inside stains hands and clothes brown — it was once used as a dye.
Late leafing
Not in leaf until mid-May. That is an adaptation against late night frost, but it makes it the tree that stays bare longest in the garden in spring.
In pictures · Furniture wood from the top shelf
Schematic drawing.
Furniture wood from the top shelf
Greyish brown with veining
A lively, unpredictable figure that is never the same twice. The sapwood is whitish and contrasts sharply.
Excellent to work
Saws, planes, carves and turns pleasantly, and takes oil and lacquer evenly.
Gunstocks
The standard for centuries, for its combination of strength, dimensional stability and shock absorption.
Scarce and expensive
Walnut trees are rarely planted for timber production, so the supply comes almost entirely from individual trees. See European walnut.
American walnut (Juglans nigra) is darker and more uniform; European walnut is lighter, greyer and livelier in figure. See walnut wood for the full difference.
Frequently asked questions about the walnut tree
Why does nothing grow under a walnut tree?
Because of juglone, a substance the tree releases through its roots, leaves and husks. It inhibits the germination and growth of many plants — tomatoes, potatoes and apples are sensitive to it.
Why does a walnut tree come into leaf so late?
As protection against late night frost. It often doesn't come into leaf until mid-May and drops its leaves again early.
Why is walnut wood so expensive?
Walnut trees are rarely planted for timber — they are there for the nuts or as solitary trees. The supply comes from individual trees, and large uniform batches hardly exist.
Can I garden under a walnut tree?
To a limited extent. Grasses, nettles and many bulbs tolerate juglone; tomatoes, potatoes and apples do not. Keep your distance to roughly the edge of the crown.
The walnut tree in perspective
Nuts above ground, chemical warfare below.
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Photo via Wikimedia Commons: Juglans regia — George Chernilevsky, Public domain