Juglans regia Seeds | English Walnut
LATIN NAME: Juglans regia
COMMON NAME: English Walnut
Plant Profile
Juglans regia is the walnut of the table, and the tree in a garden is almost always grafted. The trunk is smooth and grey, the crown is broad and open, and the leaves are pinnate with five to nine large leaflets that smell sharp when crushed. The fruit is a green husk that splits in autumn to release the familiar shell, and the kernel inside is thin-skinned and easy to extract, which is the whole point of the species.
The tree is native to the mountains of central Asia, from Kyrgyzstan to Iran and into the Himalayas, and it has been carried west for its nuts since Roman times. It grows to thirty metres in deep soil, and old trees in the Balkans and in China are often hollow and still cropping.
Science & Biotechnology
The tree produces juglone, a naphthoquinone that is toxic to many plants, and it leaches from the roots, the leaves and the husks. That is why tomatoes, potatoes and rhododendrons fail near a walnut, and why the leaves should not go into a compost that will be used on a vegetable bed. The concentration is highest in the green husk and in the roots.
The nut is rich in linoleic acid and in vitamin E, and it goes rancid quickly once shelled, which is why commercial walnuts are stored in the shell or under nitrogen. The tree is also heterozygous and highly variable from seed, so named cultivars are grafted onto seedling rootstock, usually of J. regia in Europe and of J. nigra in North America where the soil is heavier.
Uses & Benefits
The kernel is eaten fresh, roasted and pressed for oil, and the oil is used in cooking and in salad dressings. The green husk is used for dyeing and for a liqueur, and the shell is ground for abrasives and for filtration. The timber is dark, hard and beautifully figured, and it is used for furniture and for veneer, though the tree is grown for nuts rather than for wood.
In Chinese medicine the kernel is used as a tonic for the kidney, and the leaf is used as a wash for skin complaints. The bark and the green husk are astringent and were used for tanning. Walnut oil is also used as a wood finish and in oil painting, where it yellows less than linseed.
Growing from Seed
Seed needs cold and should be sown in autumn, husk removed, in a deep pot or in the ground where the tree is to stand. The taproot grows fast and resents disturbance, so do not start it in a tray. Germination is in spring, and the seedling should be planted out in its second year at the latest.
The tree wants full sun, deep soil and shelter from late frost, which damages the young shoots and the flowers. It is hardy to about minus thirty but crops best in a long, warm summer. Keep it away from a vegetable garden and from a patio, and prune only in late summer, since winter pruning bleeds and invites disease.
Our Take
Grown for the nut rather than the shade, and a tree to site carefully: the juglone will decide what grows within its reach.
Related Reading
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