Quercus agrifolia aka California Live Oak

Quercus agrifolia, also known as the California live oak or coast live oak, is a highly variable, often evergreen oak tree native to the California Floristic Province. It grows west of the Sierra Nevada mountain range from Mendocino County, California, south to northern Baja California in Mexico. This species is commonly sympatric with canyon live oak (Q. chrysolepis), and the two may be hard to distinguish because their spinose leaves are superficially similar. The coast live oak is typically a medium-sized tree, but may be shrubby depending on age and growing location. It belongs to the red oak section of oaks (Quercus sect. Lobatae). Coast live oak typically has a much-branched trunk and reaches a mature height of 10–25 meters (33–82 ft). Some specimens may attain an age exceeding 1000 years. 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 oldest specimens might exceed 20 feet in trunk circumference and 100 feet height. The leaves of the coast live oak are dark green, oval, often convex in shape, and 2–7 cm (0.79–2.76 in) long and 1–4 cm (0.39–1.57 in) 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. While the coast live oak is primarily found in its natural habitat, it can also be grown indoors as a houseplant. It requires regular watering to thrive and does best in long-lasting, direct light, being less than 1 foot from a window. Coast live oak likes soil that is well-draining and doesn't require added fertilizers if repotted each time it doubles in size.