Deciduous, monoecious trees. Leaves alternate, imparipinnate, without stipules. Flowers unisexual, epigynous, more or less actinomorphic. Male flowers in pedunculate catkins; bracteoles 2, rarely absent; perianth absent or small and 1- to 5-lobed; stamens 3 to many; filaments short; a rudimentary ovary sometimes present. Female flowers in pendulous catkins or one to few in a stiff cluster, in the axil of a bract; bracteoles 2; perianth small and inconspicuous, 1- to 5-lobed; styles 2; stigmas branched; ovary 1-celled, with 1 ovule. Fruit a drupe or winged nut; seeds without endosperm.

Contains about seven genera and over 60 species in the northern hemisphere, in temperate areas and on mountains in the tropics, and in South America.

Juglans L.

Deciduous, monoecious trees. Twigs with chambered pith. Buds with scales, sessile. Leaves alternate, imparipinnate, aromatic. Flowers unisexual. Male flowers numerous, in solitary pendulous catkins; bracteoles 2; perianth absent or small and 1–5-lobed; stamens 4–40; filaments short; a rudimentary ovary sometimes present. Female flowers in erect terminal few-flowered spikes; bracteoles 2; perianth 4-lobed; stigmas 2, simple. Fruit a large indehiscent drupe; stone (walnut) incompletely 2- to 4-celled.

Contains about 15 species in north temperate regions, south-east Asia, Jamaica and Central and South America.