Walnut, American black (Eastern black): J. nigra L.
Walnut, California black: J. hindsii (Jepson) Jepson
Walnut, Texas (New Mexico): J. cordiformis var. ailantifolia (Carr.) Rehder
Source: Magness et al. 1971
Black walnuts in the U.S. are widely distributed and are of several species, not all of which are listed. The trees vary from small, up to 20 feet, to very large, near 100 feet in height. All have long, compound leaves, with up to 20 or more leaflets. Leaflets are generally oblong-lanceolate, and smooth. In all, the nuts are encased in a semi-pulpy husk, which does not separate from the nut readily. The nut shell is thick and very hard. The kernel does not separate from the shell readily. Only the American or Eastern black is in any cultivation, and commercial cultivation of that kind is limited. Substantial quantities of the latter are gathered from native trees and marketed, mainly after shelling.