The Japanese Walnut (Juglans ailantifolia; synonyms J. cordiformis and J. sieboldiana), is a species of walnut native to Japan and Sakhalin. It is a deciduous tree growing to 20 m tall, rarely 30 m, and 40-80 cm stem diameter, with light grey bark. The leaves are pinnate, 50-90 cm long, with 11-17 leaflets, each leaflet 7-16 cm long and 3-5 cm broad. The whole leaf is downy-pubescent, and a somewhat brighter, yellower green than many other tree leaves. The flowers are inconspicuous yellow-green catkins produced in spring at the same time as the new leaves appear. The fruit is a nut, produced in bunches of 4-10 together; the nut is spherical, 3-5 cm long and broad, surrounded by a green husk before maturity in mid autumn.

Uses

The nuts have an oily texture and pleasant flavour. The husks are also used to make a yellowish dye.

The very bold, decorative leaves make it an excellent ornamental tree for planting in parks and large gardens.

Unlike the closely related and very similar North American Butternut, Japanese Walnut is resistant to the canker disease caused by the fungus Sirococcus clavigigenti-juglandacearum. This has led to its being planted as a replacement for Butternuts in North America. The two species hybridise readily; the resulting hybrid Juglans x bixbyi is also resistant to canker and is likewise planted as a replacement for Butternuts. Japanese Walnut is distinguished from Butternut by its larger leaves and round (not oval) nuts.

The wood is light and takes polish well, but is of much lower quality than Persian Walnut wood. It is often used to make furniture.

Varieties

The Heartnut is a variety of Japanese Walnut distinguished by their fruit, which is heart-shaped in cross section.

Fagales