About Juglans californica S.Watson
Juglans californica S.Watson can grow as either a large shrub with 1 to 5 trunks, or a small single-trunked tree. The main trunk may fork close to the ground, giving the appearance of two trees that grew together before diverging. Mature individuals have thick, deeply channeled or furrowed bark. Their leaves are large and pinnately compound, with 11 to 19 lanceolate leaflets that have toothed margins and no hair in the vein angles. This species produces a small hard nut, which sits inside a thick, shallowly grooved shell that is difficult to remove. While the tallest individuals can reach up to 11 meters in height, only around 10% of the population grows taller than 5 meters. Juglans californica is generally found in the valleys and adjacent slopes of the California Coast Ranges, Transverse Ranges, and Peninsular Ranges. It grows as part of mixed woodlands, and also appears on slopes and in valleys wherever growing conditions are favorable. This species is threatened by development and overgrazing. Some native stands still remain in urban Los Angeles, located in the Santa Monica Mountains, Hollywood Hills, and Repetto Hills. Juglans californica grows in riparian woodlands, forming single-species stands or growing mixed with California oaks (Quercus spp.) and Fremont cottonwoods (Populus fremontii). Climate model predictions indicate that Juglans californica may expand its range northward in response to warmer and drier conditions, and may potentially come to occupy areas currently inhabited by the endangered Juglans hindsii, also called Northern California black walnut. The nuts of Juglans californica are edible. They are eaten by the Chumash people of the Channel Islands of California and Ventura County, as well as by the Tongva people of Los Angeles County. This species is not grown commercially for food. Juglans californica is cultivated across California to support the walnut industry, where it is used as a rootstock in English walnut orchards. It is also cultivated as an ornamental tree, planted in California native plant gardens, xeriscapes, wildlife habitat gardens, and natural landscaping projects in California, as well as in Hawaii.
