"A typical oak tree will live long enough to have tens of thousands of its acorns devoured by insect larvae, birds, and mammals. Hundreds of its seedlings will wither and die among the grasses or be eaten by browsing herbivores. It will experience many onslaughts of defoliating caterpillars, twig-girdling beetles, and disease-causing fungi. Periodic droughts will cause it to become dormant and lose a whole season of photosynthesis. Wildfires will sear its bark and scorch its foliage. Floods will damage the root system, and high winds will occasionally pull away massive limbs. Despite such adversity, most tree oaks harbor the resiliency to live for centuries."

That's from Oaks of California by Bruce Pavlik (and others), a long overdue book acquisition.

Four characteristics distinguish the oak genus Quercus from other trees: the acorn fruit, distinctive wind-pollinated flowers, complex wood, longevity. Acorns arise from female flowers found singly or in small groups on young stems, while male flowers hang together in groups of 25-100 on catkins. Trees bear thousands of catkins and produce huge amounts of pollen. Oak wood comes in many colors and people put heartwood and sapwood to different uses. Mature trees can weigh several tons, and some oaks in California are over 600 years old.

California has nine native tree oak and eleven shrub oak species. Of the trees, four are deciduous, and five are evergreen. Shrub oaks cover an estimated 1.5 million acres in California. Natural variability can make identifying oaks a challenge even with a key.

The most common tree oak in coastal California where I live is the Coast Live Oak, Quercus agrifolia.

"Multiple trunks, often the result of stump-sprouting after a fire, are common and may grow as much horizontally as they do vertically. This habit limits its usefulness as a timber tree and imparts a characteristic and sometimes strange appearance to the coastal woodlands. Early California visitors wrote about the mystical beauty of this tree and the enchanted landscapes that possessed it. Some felt less enchantment and more of a haunting strangeness when first encountering these unique groves along the Pacific shore. Perhaps this is what led Robert Louis Stevenson to describe the dense coast live oak forests around Monterey as 'woods for murderers to crawl among.'"