Canyon oak, Quercus chrysolepis, is the most widely-distributed oak species in California, with its range extending beyond California into southwest Oregon, Arizona, northern Mexico, and (barely) Nevada.
On canyon oak, John Muir wrote:
The Mountain Live Oak [Quercus chrysolepis] is a tough, rugged mountaineer of a tree, growing bravely and attaining noble dimensions on the roughest earthquake taluses in deep cañons and yosemite valleys. The trunk is usually short, dividing near the ground into great, wide-spreading limbs, and these again into a multitude of slender sprays, many of them cord-like and drooping to the ground, like those of the Great White Oak of the lowlands [Quercus lobata]. The top of the tree where there is plenty of space is broad and bossy, with a dense covering of shining leaves, making delightful canopies, the complicated system of gray, interlacing, arching branches as seen from beneath being exceedingly rich and picturesque.
The authors of the excellent Oaks of California add:
Canyon oak’s growth form and other characteristics can vary greatly, allowing it to live in a variety of natural settings. No single description or portrait of canyon oak will suffice; instead, the species must be experienced and documented within the context of its many landscapes.
We only encountered the oak in a few of our collecting sites, but these ones in flats near the Sacramento River generated a bit of excitement with their particularly gold-felted cupules (chryso means “gold”, -lepis means scaled) and dimorphic leaves (holly-like on new growth, smooth-margined on mature branches).
More photos are available from CalPhotos: Quercus chrysolepis and Natural history of Orange County, California: Quercus chrysolepis. American Trees has a photograph of the Champion Tree from Oak Glen, California.