Walnut

Where it grows

The common or English walnut (Juglans regia) is native to the mountain valleys from the eastern Caucasus through Iran and Central Asia into the Karakoram. The wild walnut-fruit forests of southern Kyrgyzstan are the largest remaining and a UNESCO biosphere reserve. China and the United States now lead commercial production.

How to recognise it

A large open-crowned tree with smooth silvery-grey bark on young limbs, becoming deeply furrowed on the trunk. The pinnate leaves carry 5 to 9 oval leaflets and release a distinctive aromatic scent when crushed. The fruit is a fleshy green husk over a corrugated woody shell holding the familiar two-lobed nut.

Uses

Walnuts are eaten raw, toasted, baked into desserts, and pressed for a richly flavoured cooking oil. The deep brown heartwood — dimensionally stable, easy to carve, and resistant to shock — is the global standard for premium gunstocks, classic American furniture, and high-end cabinetry.

Allelopathy

Walnut roots and leaves release juglone, a chemical that inhibits the growth of nearby plants such as tomatoes — a phenomenon known as allelopathy.