Juglans ailantifolia

The Japanese walnut is in the Juglandaceae family and is native to Japan and Sakhalin Island in Russia. Unlike the closely related and very similar North American butternut, Japanese walnut is resistant to the canker disease caused by a Sirococcus fungus. This has led to its widely being planted as a replacement for butternuts in North America.

• Leaves are pinnate and very large, with 11–17 short-pointed toothed leaflets each 7–16 cm long and 3–5 cm broad; they are downy-pubescent.
• Species is monoecious. Male flowers are inconspicuous yellow-green catkins produced in spring at the same time as the new leaves appear. Female flowers have pink-red pistils.
• Fruit is a pitted brown, round nut enclosed in green husk 5 cm long and with sticky hairs, in bunches of 4–8 nuts.
• Japanese walnut is distinguished from butternut by its larger leaves and round (not oval) nuts.