Juglans
Walnut trees are any species of tree in the plant genus Juglans, the type genus of the family Juglandaceae, the seeds of which are referred to as walnuts. All species are deciduous trees, 10–40 metres (33–131 ft) tall, with pinnate leaves 200–900 millimetres (7.9–35.4 in), with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya), but not the hickories (Carya) in the same family.
The 21 species in the genus range across the north temperate Old World from southeast Europe east to Japan, and more widely in the New World from southeast Canada west to California and south to Argentina.
Etymology
The common name walnut derives from Old English wealhhnutu, literally 'foreign nut' (from wealh 'foreign' + hnutu 'nut'), because it was introduced from Gaul and Italy. The Latin name for the walnut was nux Gallica, "Gallic nut".
The generic name comes from Latin jūglans, meaning 'walnut, walnut tree'; jūglans in turn is a contraction of Jōvis glans, 'nut of [the god] Jupiter'.
