Walnut

Walnut trees have long compound leaves with 5 to 23 short-stalked leaflets. The male and female reproductive organs are borne in different petal-less flower clusters, known as catkins, on the same tree. The twigs characteristically contain a many-chambered pith. The fruit is not a true botanical nut: it is a drupe with the edible seed (commonly called a nut) enclosed in a shell within a thick husk.