Deciduous trees, rarely shrubs, monoecious; bark smooth or furrowed. Branchlets with partitioned pith, sparse to densely glandular. Leaves alternate, odd-pinnate; leaflet margins usually serrate. Male catkins pendulous, produced on previous year’s growth. Male flowers usually with numerous stamens. Female catkins solitary, erect, produced on current season’s growth; bracts entire, bracteoles 2 per flower; perianth 4; style branches plumose. Fruit a drupe-like nut with thick dehiscent or indehiscent husk covering a thick, wrinkled- or rough-shelled nut.
About 20 species, mainly from the Northern Hemisphere, also in South America; 2 species naturalised in Australia, 1 naturalised in Victoria.