The northern limit of its growth is in southern Oregon. It goes south from there on the coast ranges of California and the western slopes of the Sierra Nevadas to the highlands of southern California. Its growth on the mountains of southern Arizona and New Mexico is always shrubby. The lowest limit of its range is about 1,000 feet above sea level, the best specimens occurring at low altitudes in the sheltered canyons of the coast ranges of California. Gradually diminishing in size, it grows to the very tops of many of the high mountains, sometimes reaching 9,000 feet, being not more than a foot high at the upper limits of its range. In appearance this tree resembles the eastern live oak (_Quercus virginiana_), having the same majestic wide-spreading crown, except in the high altitudes where it forms dense thickets covering large areas.
When in its favorite habitat, the massive proportions and majestic appearance of this tree are imposing, the crown sometimes being 150 feet across, the bole short and thick, and the great branches long and horizontal. It is not clothed in the somber Spanish moss that is often present on the great live oaks of the southeastern states, but there is a similarity of appearance in the drooping slender twigs. One hundred and fifty feet across is cited as an unusual width of crown, one hundred feet being a good average size, and forty or fifty feet the usual height, although it sometimes reaches 100. The bole is vested in a gray-brown, reddish-tinged bark, about an inch thick, and broken into numerous scales which in old age become flaky and pliable and fall off.
The bark is light colored, and has the stringy character of white oak. The tree would readily pass for a white oak were it not for its two-year acorns which class it in the black oak group. The wood resembles white oak, and weighs 52.93 pounds per cubic foot.
Few oaks, if any, retain their leaves a longer time than this. They remain on the branches three or four years. Most evergreen oaks shed theirs at the beginning of the second year. The leaves of this tree are peculiar in another way. They assume various forms. That in itself is not unusual and occurs with many species; but the canyon live oak has one pattern of leaf for the young tree, another for the old. One form has a margin with sharp, hooked teeth; another has smooth-margined leaves, and there are various intermediate forms. Sizes vary no less than shapes of both acorns and leaves. Some acorns are half an inch in length, others two inches.