Quercus Agrifolia - Habitat and Ecology

Habitat and Ecology

Coast Live Oak is the only California native oak that actually thrives in the coastal environment, although it is rare on the immediate shore; it enjoys the mild winter and summer climate afforded by ocean proximity, and it is somewhat tolerant of aerosol-borne sea salt. The coastal fog supplies relief from the rainless California summer heat.

It is the dominant overstory plant of the Coast Live Oak woodland habitat, often joined by California Bay Laurel and California Buckeye north of Big Sur. Associated understory plants include Toyon, various manzanitas and Western Poison-oak.

Normally the tree is found on well drained soils of coastal hills and plains, often near year round or perennial streams. It may be found in several natural communities including Coast Live Oak woodland, Engelmann Oak woodland, Valley Oak woodland and both northern and southern mixed evergreen forests. While normally found within 100 kilometers of the Pacific Ocean at elevations less than 700 meters, in southern California it occasionally occurs at up to 1,500 meters in altitude.

The California Oak Moth (Phryganidia californica) caterpillar subsists entirely on living and fallen leaves of the Coast Live Oak. In 8-10 year cycles, the caterpillar will appear in sufficient abundance to denude healthy trees. The trees recover, and botanists speculate that the species provide mutual benefit, possibly in the form of fertilizer for the oak . The Coast Live Oak is also the only known foodplant of Chionodes vanduzeei caterpillars.