The butternut is indigenous to North America, growing in the eastern part from the 35th parallel northwards to Canada. It occurs in mixed, broad-leaved woods, alongside rivers and in hill country, on deep, fertile soils, attaining heights of up to 30 metres. The bark is grey, divided by shallower fissures than those of the black walnut. The twigs and buds are grey, sticky-pubescent, and the pith of the twigs contains air spaces. The male flowers resemble those of the black walnut, the female flowers are borne in a stalked spike. The fruit is an ovoid, pointed drupe, 4 to 5 cm long, attached by a stalk approximately 10 cm long. When ripe, it falls from the tree in its entirety, including the yellowish green, sticky-pubescent husk. The nut is sweet and oily.
The butternut is resistant to frost and requires less fertile and moist soils than the black walnut. However, as it grows more slowly and the wood is not of high quality, it is cultivated in Europe mainly as an ornamental specimen tree in parks and gardens.
Leaves: 40—70 cm long, odd-pinnate, composed of 11—13 ovate leaflets; the rachis and underside of the leaflets are glandular pubescent. Flowers: Female borne in spikes of 5—8. Fruit: Ovoid nuts in clusters of 3—6; nut shell deeply corrugated.