The wild California  Blackberry  is a sprawling, competitive plant, very stickery; it likes moist locations.  Its  small fruit was an ancestor to the boysenberry and loganberry.  Source

The blackberry bramble provides thick cover for birds and animals (e.g. rodents)   and is an important source of food, especially for birds.  The flowers attract honeybees and bumblebees.

California Indians ate the berries (a good source of Vitamin C), either dried or fresh. 

With its pattern of three leaves,  the California blackberry may look like poison oak at first glance, but the stickers tell us it is not.

New plants start from regrowth from the crown, underground shoots, and seeds (often dispersed by birds and animals).  The bush creeps outward and becomes very wide and thick  in time.  Source