Quercus kelloggii

California black oak


The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta (flowering plants). Class - Magnoliopsida (dicotyledons). Subclass - Hamamelididae. Order - Fagales. Family - Fagaceae (beech). Genus - Quercus L. (oak). Species - Quercus kelloggii Newberry (california black oak).

Ecology: California black oak is typically 9-25 m in height and 0.3-1.4 m DBH at maturity. Large trees may exceed 36 m in height and 2 m DBH. On open, fertile sites form is tall and straight, with a clean bole and a broad, rounded crown...California black oak has thin, smooth bark when young. Bark becomes moderately thick, deeply fissured, and platy with age. California black oak grows from one to several taproots that may penetrate to bedrock.
California black oak is the only western oak species in the red oak subgenus that is deciduous. The deeply lobed leaves are typically 10-20 cm long. Acorns are relatively large in this species, from 2.5-3 cm long and 1.5-1.8 cm wide.

Interesting Uses

Many Native American villages were located near California black oak groves, and acorns - particularly California black oak acorns - were a primary source of tribal wealth. Tribes preferred California black oak acorns over those of other oak species for making acorn meal because of California black oak meal's superior taste and pudding-like texture when cooked. California black oak meal was often mixed with other oak meals to improve meal flavor and texture. Native Americans used California black oak meal to make soup, bread, and pudding. Moldy California black oak flour was used to treat boils and sores.

California black oak is a critical species for wildlife. Oaks 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 oak species. Its acorns are the largest of the western oaks, and are heavily consumed by livestock, mule deer, feral pig, rodents, mountain quail, wild turkey, jays, and woodpeckers. California black oak woodlands are important habitat for several rare and threatened species. California black oak provides diversity and nesting and other cover for California spotted owls and flammulated owls.


California black oak is highly susceptible to wood-decaying fungi. Heart rot is mainly caused by two fungal pathogens: Inonotus dryophilus and Laetiporus sulphereus. Another fungus, Armillaria mellea, causes root and butt rot in old or fire-damaged trees. Sprouts arising from infected boles are susceptible to heart rot. Summer irrigation encourages growth of root rot fungi. California black oak and other oaks in the red oak subgenus are vulnerable to "sudden oak death disease". Both the origin and life cycle of the fungus-like water mold (Phytopthora ramorum) causing this disease are unclear.

This species is frequently infested with Pacific mistletoe.

Fire effects: California black oak is an early seral species that requires light for rapid growth. Surface fires thin the canopy and create small openings for California black oak seedling establishment by killing fire-intolerant, late successional conifers. California black oak has several adaptations that enable it to survive fire. Its thick, insulating bark protects it from low- and most moderate-severity surface fires. If top-killed, it sprouts from the root crown. Its extensive root system has large nutrient and water reserves and is capable of supporting prolific sprouting. California black oak also establishes from acorns after fire. Dispersal of off-site acorns by seed-caching animals probably allows for burn colonization.
Native Americans increased historical fire frequency in yellow pine types, including ponderosa pine, through intentional use of fire. Very frequent fire-return intervals converted the forests to oak woodlands on some sites. Along with patchy stand-replacement fire, Native American fires were critical in maintaining California black oak as a cover type.


Seed Production - California black oak is monoecious and outcrossing. Although there are generally more California black oaks of sprout than seedling origin, California black oak "can produce adequately from seed". California black oak acorns require 2 years to develop and ripen. Abortion of first-year acorns is common, especially during drought...California black oak is a masting species, with high acorn production in some years and low production in others.

Seed Dispersal - Animals and gravity disperse the acorns. Since California black oak acorns are heavy, those not dispersed by animals tend to fall beneath the parent tree's crown, which suppresses seedling growth. Seed-caching animals are the most important acorn dispersers. Unretrieved seed buried in caches is more likely to germinate and establish than seed in litter or on the ground. A few hours of direct sunlight or sustained indirect heat kills California black oak embryos. California ground squirrels, western gray squirrels, Steller's jays, and scrub jays are important California black oak acorn cachers.

Seed Bank - California black oak has a short-term seed bank. Acorns in the field lose viability rapidly when warm fall or spring temperatures desiccate the embryo, although California black oak acorns remain viable for 2 to 5 years under laboratory storage conditions. Acorns in litter and buried in animal caches form a temporary seed bank and may survive several months.

Vegetative Regeneration - California black oak sprouts from the root crown or bole after fire, logging, frost, or other top-killing events. Edwards and McDonald state that most California black oak stands originate from sprouts. Sprouting is California black oak's primary method of reproduction after top-killing events like fire. Even seedlings sprout after top-kill, and sprouting ability is retained until trees are "very old and moribund". Old California black oaks may not sprout if perennating buds are covered by thick bark. Trees originating from root crown sprouts are often multistemmed...Open structure and dormant-season disturbances promote initially high sprout densities.

Species Distribution


USDA Plant Database
USDA, NRCS. 2016. The PLANTS Database (http://plants.usda.gov, 4 February 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA.

Flora of North America
Flora of North America Editorial Committee, eds.  1993+.  Flora of North America North of Mexico.  19+ vols.  New York and Oxford.

Silvics of North America
Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

Intermountain Herbarium
Consortium of Intermountain Herbaria. 2016. http//:intermountainbiota.org/portal/index.php. Accessed on February 04.

Jepson Manual
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA. $131.95, hardcover; 1600 pages. ISBN-13: 978-0520253124.

USGS Plant Species Range Maps
Critchfield, W.B., and Little, E.L., Jr., 1966, Geographic distribution of the pines of the world: U.S. Department of Agriculture Miscellaneous Publication 991, p. 1-97.
Little, E.L., Jr., 1971-1978, Atlas of United States trees, volume 1,3,13,17, conifers and important hardwoods: U.S. Department of Agriculture Miscellaneous Publications.