This looks quite different to Frangula I see in the Santa Monicas, but not sure it could be anything else.
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Rhamnus californica (syn. Frangula californica), commonly known as coffeeberry and California buckthorn, is a species of flowering plant in the family Rhamnaceae, the buckthorns. It is native to the southwestern United States and Baja California in Mexico. It is an introduced species in Hawaii.