As many as 20 different types of oak trees grow native in California, including oaks that lose their leaves and oaks that are evergreen. The oak trees of California take the form of true trees in some cases and are shrubs in others.
California oak trees often must grow in places where water is scarce, meaning that many types do well in dry settings. Among the oaks of California are the black oak, blue oak and canyon live oak.
California Black Oak
The California black oak can tolerate dry soil, which makes it able to survive periods of drought better than other trees can. California black oak can grow to 100 feet but typically remains in the height range of 50 feet. The tree has ridged black bark that gives it its name, and possesses leaves that have from five to seven separate pointed lobes, each with a bristle at the end. The leaves are as long as 6 inches and as wide as 3 inches and their green color changes to orange, red and yellow tones in autumn. The trunk of this species is usually short, with a round canopy of branches.
Always place a California black oak in acidic soil for it to flourish. It can grow at elevations up to 8,000 feet and is a common oak in the Sierra Nevada Mountain region of California. The tree will require some shade in hot climates; water it at least one time each week as it matures until it establishes itself. California black oak produces inch-long acorns that were once a major part of the diet of the state's Native Americans.
The blue oak is an endemic species in California, found only there and nowhere else. The tree grows in open areas in the state and it will survive extreme drought scenarios. It develops a round canopy comprised of multiple crooked branches and only grows to an average size of about 30 feet, according to the Blue Planet Biomes website. The leaves of blue oak come off during the California winter, unless the tree sheds them before that during a time of drought and goes into a dormant state.
Blue oak leaves have a wax-like coating, and are thick and designed to conserve moisture. The leaves are as long as 3 inches and have seven lobes in most instances. The tree takes its name from the green-blue color of the leaves. Blue oaks can send roots down as far as 80 feet into the soil in search of water. Avoid overwatering a blue oak, as the tree does not require excessive water and it will precipitate a fungus that will attack the roots in the soil.
Canyon Live Oak
The canyon live oak can be as tall as a shrub or grow to 100 feet high, depending on the soil and where in the state that you find it growing. Canyon live oak grows to its tallest heights in the fertile soil found in the bottoms of the canyons of California. The tree tolerates the shade and can adapt to dry conditions if necessary.
The species has evergreen leaves that will last on the tree for as long as three to four years before falling off as new leaves replace them. The leaves are oval and 1 to 4 inches long. Some have smooth edges while others resemble holly leaves, with distinct teeth. The trunk of this species is typically short and the crown very wide, making for a spreading tree that is an attractive sight. This allows you to use it as a specimen tree out in the open if you desire.
One of the most appealing facets of the canyon live oak is its acorns. The fruit is an inch and a half long and has a wool-like golden cap that gives the tree the nickname of Golden Cup Oak.