California black oak is a native, deciduous tree, typically growing from 30 to 80 feet (9-25 m) in height and from 1 to 4.5 feet (0.3-1.4 m) in diameter. Large trees may exceed 120 feet (36 m) in height and 5 feet (1.6 m) diameter. The species also grows in scrub form on poor sites. In open areas the crown is broad and rounded, with lower branches nearly touching the ground or forming a browse line. In closed stands, the crown is narrow and slender in young trees and irregularly broad in old trees. Trunks are usually free of branches for 20 to 40 feet (6-12 m) in closed stands. Trunks are often forked, and usually decayed and hollow in older trees. The bark is thin and smooth in young trees, becoming moderately thick, deeply fissured, and platy with age. This oak grows from one to several vertical roots which penetrate to bedrock, with large, laterally spreading roots extending off from vertical ones. It also has a number of surface roots. Acorns are relatively large in this species, from 1 to 1.2 inches (2.5-3 cm) long and 0.6 to 0.7 inch (1.5-1.8 cm) wide. The deeply lobed leaves are typically 4 to 8 inches (10-20 cm) long . California black oak can live up to 500 years of age.
California black oak is distributed along foothills and lower mountains of California and southern Oregon. It is found from Lane County, Oregon south through the Cascade Range, the Sierra Nevada, and the Coast, Transverse, and Peninsular ranges to San Diego County, California. The tree occurs in pure or mixed stands. Pure stands usually indicate sites unfavorable to conifer growth or reoccurring disturbance such as fire or logging activities.
California black oak is used for making cabinets, furniture, high grade lumber, pallets, and industrial timbers. It is also used as fuelwood.
California black oak comprises a total volume of 29 percent of California's hardwood timber resources, and is the major hardwood sawn into lumber in that state. The total estimated area of species occurrence is 894,000 acres (2.24 million ha): 591,000 acres (1.48 million ha) of timberland and 303,000 acres (757,500 ha) of woodland. Sixty percent of this land is privately owned; 31 percent is in National Forests; and 9 percent is on other public lands. California black oak has greatly decreased from historic numbers, however. This is due to a number of factors, including drought, animal foraging, logging practices, fire suppression, and a variety of other human impacts. Cutting green trees for fuelwood has contributed to the decline of this species, and illegal harvesting of green trees from public lands is a continuing problem.
Plantations of California black oak have been successfully established in clearcuts from acorn plantings. Thinning such stands promotes stand productivity and wood quality, and is recommended when trees are from 30 to 50 feet (9-15 m) tall or when stand density exceeds 125 square feet of basal area per acre (29 sq m/ha). This tree has also been managed for hardwood production by maintaining scattered pure stands within coniferous forests. Stands of this species will often establish on poorer sites, where conifer seedling establishment has not been successful.
California black oak is a critical species for wildlife. Oaks (Quercus spp.) may be the single most important genus used by wildlife for food and cover in California forests and rangelands, and California black oak occupies more total area in California than any other hardwood species. Livestock also make heavy use of this species for food and cover.
Cavities in California black oak provide den or nest sites for owls, various woodpeckers, tree squirrels, and black bear. Trees provide valuable shade for livestock and wildlife during the hot summer months. California black oak forest types are heavily used for spring, summer, and fall cover by black bear.
California black oak is browsed by mule deer and livestock. Acorns are heavily utilized by livestock, mule deer, feral pig, rodents, mountain quail, Stellar's jay, and woodpeckers. Acorns constitute an average of 50 percent of the fall and winter diets of western grey squirrel and black-tailed deer during good mast years. Fawn survival rates increase or decrease with the size of the acorn crop.
California black oak is a preferred foraging substrate for many birds. All of 68 bird species observed in oak woodlands of the Tehachapi Mountains[?] of California used California black oak for part of their foraging activities. The acorn woodpecker, the Northern oriole, and the Nashville warbler showed greatest preference for California black oak.
California Indians preferred California black oak acorns over those of other species for making acorn meal.