Sadly, this attractive medium-sized tree is seriously threatened by a deadly fungus in its native range. Its species epithet is from the Latin cinereus meaning ‘ashy’, referring to its bark colour. Introduced to north-west Europe in the seventeenth century.

Native to south-east Canada and the eastern USA but largely absent from southern states. Uncommon in north-west Europe, where it is possibly under-reported as easily confused with Black Walnut (p. xxx).

Monoecious, relatively short-lived (75 years). Wind-pollinated. Seeds distributed by birds and mammals.

Medium (25m), often slender. Bark ash-grey, splitting into shallow plates. Twigs initially felty, sticky and red-haired, with roughly triangular leaf scars topped by a velvety 'moustache'; terminal buds large (12-18mm). Foliage smells citrus with a hint of pine. Leaves pinnate compound, very large (30-60cm), with 11-17 serrated leaflets, hairy beneath. Fruit a sticky-husked ovoid drupe (3-6cm) in clusters of 2-6. Black Walnut differs: darker bark, notched moustache-less leaf scars, glabrous foliage.

Among the hardiest of all walnut species. Does not tolerate shade. Thrives best in fertile, deep loams with good drainage.

No notable associations where introduced.

Considered endangered in much of its native range due to butternut canker (Ophiognomonia clavigignenti-juglandacearum), an invasive, lethal fungus. So far, the pathogen is not present in Britain or Ireland.

Fruit (nuts) are very oily with a buttery flavour. Timber is soft and without the qualities of Black Walnut or Common Walnut.