The centre of the walnut’s natural range is in central Asia, from where it extended as far as the Balkan Peninsula. It was cultivated by the Greeks and Romans, the boundary of its distribution shifting markedly northward. Today it is widely planted in western and central Europe, the U.S.A. And other countries. It is a tree which in central Europe does best on sheltered slopes in warm, hill country. On limestone rock it grows up to elevations of 700 to 800 metres.
A light-demanding species, the walnut requires fertile soil, and, in severe winters can suffer from frost damage. The young tree has a taproot, but in old trees the root system spreads to a distance of 15 metres from the trunk. The bark is ash-grey with shallow fissures. Open-grown trees have a short trunk and spreading crown. Under ideal conditions it can attain 30 metres in height. As in all walnuts the pith of the twigs forms plates and partitions with air spaces in between.
The tree is cultivated in gardens and avenues for its fruit — nuts — which it begins to bear from about its tenth year. The green husks split in September and October to release the nuts, whose oily kernel is very tasty and nourishing. The high quality wood (the heartwood is brownish, the sapwood greyish) is used to make furniture, rifle stocks and other special articles.
Leaves: 20—35 cm long, odd-pinnate, composed of 5—9 leaflets with entire margins, the terminal leaflet being the longest.
Flowers: Male in catkins 5—15 cm long, female in 1—4 flowered spikes, each with two stigmas. Fruit: Ovoid drupe with nut encased in a fleshy husk.