General: Oak family (Fagaceae). Tanoak is an evergreen hardwood tree or shrub native to the west coast ranges from Southern Oregon to Southern California. The plants can reach 20 to 45 meters in height with the stems of large trees reaching up to 1 meter in diameter. The form and size of tanoak is variable depending on the environment. Taller forms generally occur in shady forests and shorter forms in open areas where sunlight is more abundant. However, the trees can have a shrub-like form with multiple stems when access to light is prevented, such as when growing in a dense forest understory. Mature trees growing in a more open forest have a single, short trunk with horizontal branches.

The thick, leathery evergreen leaves are oblong in shape with pointed tips (4 to 10 cm long). The leaves have noticeable parallel side veins on the undersides that are evenly spaced and run from the central vein of the leaf ending in a pointy tooth at the leaf margin. New leaves are covered with reddish-brown hairs, which turns whitish as they mature. Older leaves are a smooth green on top with lightly pubescent gray-green below. The evergreen leaves remain on the tree about 3 to 4 years before they are shed. The light reddish-brown bark develops deep fissures as the trees age. Large clusters of tiny white flowers bloom in the summer months in the leaf axils of the current seasons growth. The flowers are erect catkins and have an odor that is not pleasant. The acorns are from 2.5 to 5 cm long with a diameter of about 1.5 to 1.8 cm and grow singly or in cluster. Tanoak acorns have hairy, rather than scaly caps of the true oak. Acorns ripen in the fall of the second season.

Distribution: Tanoak occurs on fertile mountain slopes and ridges below 1200 meters in the Coast Ranges from the Santa Inez Mountains in Southern California, to the Cascade Ranges in Southwestern Oregon. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Habitat: The tree form is a major part of the coastal redwood forest, Douglas fir forest, and mixed evergreen forest while the shrub form is a component of chaparral communities.