There are a number of common oak species in California including both tree species and shrub species.
Black Oak (Quercus kelloggii) Found in hilly regions between 2,000 and 6,000 feet. Typically associated with conifers and pines, firs, or incense cedars.
Blue Oak (Quercus douglasii) Found in the hot, dry interior foothills. Generally found below 3,500′.
Canyon Live Oak (Quercus chrysolepis) Evergreen oak found in foothills, steep canyons, and on slopes to 9,000′.
Coast Live Oak (Quercus agrifolia) Evergreen oaks found in coastal fog zones and in grassland savannas.
Engleman or Mesa Oak (Quercus engelmannii) Rare species found in scattered groups along the western edge of California deserts.
Interior Live Oak (Quercus wislizenii) Evergreen species usually found on uploand slopes below 5,000 feet , in low foothills and in hot dry canyons.
Island Oak (Quercus tomentella) Found on the Channel Islands off the coast. Typically in foggy areas often on north or north west facing slopes.
Oregon Oak (Quercus garryana) Found away from coastal fog on slopes and open valleys, usually between 1,000 and 5,000 feet
Shreve’s Oak (Quercus parvula var. shrevei) Similar in appearance, often found growing adjacent to, and may produce hybrids with Coast Live Oak.
Valley Oak (Quercus lobata) A deciduous tree species that can grow very large. Found typically inland from the coastal fog region, usually below 2,000 feet.