Juglans californica of the genus suggests "J. californica" is sister to the remaining black walnuts (section Rhysocaryon). This article follows the conventions of "The Jepson Manual". Juglans californica Juglans californica, the California black walnut, also called the California walnut, or the Southern California black walnut, is a large shrub or small tree (up to 30 feet tall) of the walnut family, Juglandaceae, endemic to California. "Juglans californica" is generally found in the southern California Coast Ranges, Transverse Ranges, and Peninsular Ranges, and the Central Valley. It grows as part of mixed woodlands, and also on slopes and in valleys wherever conditions are
Castanea sativa the plant can’t pollinate itself, making cross-pollination necessary. Some cultivars only produce one large nut per cupule, while others produce up to three nuts. The nut itself is composed of two skins: an external, shiny brown part, and an internal skin adhering to the fruit. Inside, there is an edible, creamy-white part developed from the cotyledon. The tree requires a mild climate and adequate moisture for good growth and a good nut harvest. Its year-growth (but not the rest of the tree) is sensitive to late spring and early autumn frosts, and is intolerant of lime. Under forest conditions, it