The California Black Walnut is a small tree that can grow as tall as 49 feet, but is usually found about half that size. It is endemic (limited) to California. It can be found in most of the open spaces in valleys, and open slopes, in mixed woodlands that might include cottonwood trees and native oaks. Overgrazing and development threaten these lovely trees. Although these trees are not grown commercially, they were eaten by the local Native Americans.