California Black Walnut

Juglans californica

Common on hillsides in oak woodland and grassland with scattered trees in Chino Hills, Santa Ana Canyon and Santa Ana Mtns.  There are trees that were planted in 1974 along SR74 which are now propagating into adjacent wilderness areas.   

Walnuts are monoecious, bearing separate male and female flowers on the same tree. Petals and sepals are lacking from both types of flower. Catkins (male inflorescences) are produced laterally on one-year old wood, and female flowers are produced terminally in spikes of 2-6 on current season’s wood. Walnuts are self-fertile and wind-pollinated, but self-fertilization is prevented because male flowers shed pollen before the female flowers on the same tree can receive it.

Although many trees and small populations have established themselves through Orange County, probably the only naturally occuring populations are those in the Northern portions of the county. Others trees, such as along Santiago Canyon Road, Laguna Canyon Road, Silverado Canyon Road and elsewhere are probably all from cultivation.

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