When I first moved to California, many years ago, I knew only Eastern deciduous oaks: trees with interesting leaves with cutouts that turn color and drop every fall. In the face of months of snow and freezing temperatures, those oaks grow large, thin leaves that are killed by the first hard frost and drop to the ground as mulch.
I accepted California evergreen oaks as part of the state’s balmy strangeness. Our local oak trees are those now-familiar green giants, Coast Live Oaks. Their smaller tough leaves are oval, with varying numbers of sharp points around the margins. The two kinds of oaks follow different survival strategies: winter deciduous and evergreen. And then a few years ago, I began to notice places where both types grow.
Live oaks grow mainly on the coast, where it never gets cold enough to freeze the leaves. The oaks grow toward the bottom of the canyons, just enough upslope to survive the freezing air that turns willow and sycamore leaves yellow and red. So the oaks can put their energy into building tough, long-lasting leaves.