Juglans 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, tall, with pinnate leaves , 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. The
Juglans californica "J. californica" grows in riparian woodlands, either in single species stands or mixed with California's oaks ("Quercus" spp.) and cottonwoods ("Populus fremontii"). "Juglans californica" can be either a large shrub with 1–5 trunks, or a small, single-trunked tree. The main trunk can fork close to the ground, making it look like two trees that have grown together, then diverged. It has thick bark, deeply channeled or furrowed at maturity. It has large, pinnately compound leaves with 11–19 lanceolate leaflets with toothed margins and no hair in the vein angles. It has a small hard nut in a shallowly grooved, thick