As a source of walnuts, pecans and hickory nuts and as a source for oil and fine timber. Fossil pollen in the Paleocene and fossil wood from the Eocene. Flowers are small and greenish, apetalous.
Inflorescence is as a hanging catkin for male flowers, female flowers are erect.
Both subtended by bracts. Fruit a drupe or nut. Seed with endosperm lacking. Placentation is basal. Habit is as small to large trees.