This is a large Coast Live Oak. It started growing over 250 years ago: Before Silicon Valley, before the Valley of Hearts Delight. The first name of Sunnyvale, Encinal, was from the spanish word for the coast live oak.
Quercus agrifolia, the coast live oak, is an evergreen oak. It grows west of the Sierra Nevada from Mendocino County, California, south to northern Baja California in Mexico. Coast live oak typically has a much-branched trunk and reaches a mature height of 10–25 meters. Some specimens may attain an age exceeding 250 years, with trunk diameters up to three or four meters, such as those on the Filoli estate in San Mateo County.
The trunk, particularly for older individuals, may be highly contorted, massive and gnarled. The crown is broadly rounded and dense, especially when aged 20 to 70 years; in later life the trunk and branches are more well defined and the leaf density lower.
The leaves are dark green, oval, often convex in shape, 2–7 cm long and 1–4 cm broad; the leaf margin is spiny-toothed (spinose), with sharp thistly fibers that extend from the lateral leaf veins. The outer layers of leaves are designed for maximum solar absorption, containing two to three layers of photosynthetic cells.
These outer leaves are deemed to be small in size to more efficiently re-radiate the heat gained from solar capture. Shaded leaves are generally broader and thinner, having only a single layer of photosynthetic cells. The convex leaf shape may be useful for interior leaves which depend on capturing reflected light scattered in random directions from the outer canopy.