Family: JUGLANDACEAE
There are about 15 species of walnut, having a wide natural distribution from Europe to China, Japan and the Americas. Walnuts require a minimum rainfall of 760 mm (less with irrigation), a deep, rich soil which is well drained to a depth of at least three metres and containing large amounts of humus. The site must be free from extreme heat and late spring frosts. They are traditionally spaced 15 m x 15 m, although closer spacings of l 2 m x 15m and 9 m x 15 m have produced greater yields per hectare. The closer spacings would be preferable for long term timber production, as they would result in longer trunks.
The leaves of walnuts, when fed to dairy cows are said to increase the butter - fat content of milk.