BLACK OAK, WHITE OAK
A Succinct Guide to Distinguishing the Two Species
California is home to more than 20 species of oaks, 10 of them occurring here in the Northwest corner of the state. Of these 10, six are evergreen and four are deciduous, losing their leaves in the fall. Two of our most beautiful species are deciduous: black oak, Quercus kelloggii, and white oak, sometimes called Oregon oak, Quercus garyanna. At a glance, the two species of oaks are somewhat similar in appearance, but there are differences you can look for to tell the two apart. Leaves of both species are lobed, but black oak leaves have a sharp spine at the tip of each lobe while white oak leaves do not. White oak leaves are more deeply lobed, with the innies, called sinuses, cutting closer to the center vein of the leaf. Bark on black oaks is smooth and grey in youth, becoming rough, narrowly fissured and dark, hence the common name black oak. Bark on white oaks is light in color, and not as rough or deeply fissured. Acorns of the black oak are big, up to 1½ inches long, dark brown when ripe, and the cup, or hat, covers about a third of the nut; whereas white oak acorns are no larger than 1¼ inches long, ripen to light brown and bulge out from a small cup. Black oak trees grow up to about 80 feet, noticeably taller than white oaks, which can grow up to about 60 feet, although there are outliers of both species growing even taller.
Oak trees provide habitat to large numbers of caterpillars, which in turn are eaten by other animals in the food web or mature into pollinating moths and butterflies. Oaks are thus considered Keystone Species: species that have an outsized impact in supporting the ecosystems in which they are found. Acorns provide food for many creatures and are sought by deer, bears, rodents, and birds. The nutritional value of acorns is high, providing needed fats, protein, carbohydrates, and many essential amino acids as well as vitamins A and C. Since time immemorial, acorns were a primary food source for many of California’s indigenous people, black oak and tan oak being the preferred species, and many people continue the labor-intensive practice of processing acorns for food.
White oak is found from southern British Columbia through mountain ranges south to Los Angeles County, with the largest individuals in Oregon’s Columbia River region. In California it occurs most predominantly in the North Coast Range. Black oak is found from Southwestern Oregon through mountain ranges south to San Diego County, occurring most predominantly in the North Coast Range and the Sierra Nevada. Oaks are in the beech Family, along with chestnut and chinquapin.
Cheryl Lisin is a native plant enthusiast, landscape designer, and President of Friends of the Lost Coast, whose mission is to inspire passion for nature in the Lost Coast region. She is currently working on a native plant garden and nursery at the King Range BLM office for the education and enjoyment of all. You can contact her at [email protected].