Quercus kelloggii aka California Black Oak

Quercus kelloggii, or California black oak, is a deciduous tree. It belongs to the beech family, Fagaceae. Its native range runs from southwest Oregon through California. Kew extends that range into northern Baja California, Mexico. It grows in foothills and mountains, sometimes among conifers. Wild trees occur on clay and gravelly ground.

Trees reach about 40–80 feet [12–24 metres] tall. Plants For A Future gives an upper height of 82 feet [25 metres]. The crown has an open, rounded shape. At high elevations, plants may form large shrubs instead. These can reach 15 feet [4.5 metres] tall. Young trees have smooth, dark grey to black bark. Age brings thick bark with broad, uneven plates and ridges. Reddish-brown twigs bear pointed buds in clusters at their tips.

Leaves grow in an alternate pattern along the twigs. Each leaf has deep or shallow lobes with bristle-tipped teeth. The upper side shines green; the underside looks paler. New leaves may show soft pink tones and fine hairs. Fall brings yellow or yellow-orange leaves. Small flowers appear with the new spring leaves. Male and female flowers grow on the same tree. Wind carries the pollen, and Plants For A Future lists May flowering. Acorns take two growing seasons to mature. Their deep cups cover about half of each nut.

Grow this oak in sun or light shade. It tolerates drought and dry, sandy or gravelly soil. Deep, fertile loam also suits it, including heavier ground. Plants For A Future notes a preference for moist soil. Sources differ on cold limits, giving USDA zone 7 or zones 8–11. Warm summers help the wood mature before winter. Poor summer growth can lead to frost damage in Britain. The tree tolerates wind but not coastal exposure. Its rounded crown suits specimen planting and woodland gardens. Surface roots can cause problems in landscape settings.

Several Indigenous North American peoples used the acorns as food. The seeds contain bitter tannins that need leaching before cooking. Ground seeds can thicken stews or join flour for bread. Plants For A Future reports no known hazards. Insect larvae can cause galls on the tree. These galls provide tannins and dyes, with reported medicinal uses. Fresh leaf mulch can hinder other plants' growth. Young trees form deep taproots and become hard to transplant.