Juglans cinerea x ailantifolia

The 'buartnut' was developed as hybrid between the butternut (J. cinerea) and Japanese walnut (J. ailantifolia var. cordiformis) because the butternut was being seriously infected by butternut canker disease, leading to its decline. The new hybrid shows good resistance to the butternut canker. In fact, many of the butternuts planted in North America are now either the hybrid or Japanese walnut.

The American butternut, the Japanese butternut and the buartnut cross between themselves and are quite similar in appearance and often are mistaken for each other.

• Leaves are alternate, pinnately compound, 40–70 cm long, with 11–17 leaflets, each leaflet 5–10 cm long and 3–5 cm broad. The whole leaf is downy-pubescent, bright green.
• Species is monoecious. Male yellow-green catkins are up to 12 cm long; females are on solitary short stems, in groups, near ends of twigs, with small, light-pink pistils, in early summer.
• Bud scars are "happy face", with hairy eyebrows; terminal bud is hairy, leaf-like appearance; pith is chambered, chocolate brown.
• Fruit is an oblong-ovoid nut 3–6 cm long and 2–4 cm broad, surrounded by a green husk, produced in bunches of two to six together.