valley oak (Trees & Shrubs of the Sunol Region

valley oak

Quercus lobata

Summary ⁷

Quercus lobata, commonly called the Valley oak, grows into the largest of North American oaks. It is endemic to California, growing in the hot interior valleys and foothills. Mature specimens may attain an age of up to 600 years. This deciduous oak requires year-round access to groundwater.

Description ⁸

General: Oak Family (Fagaceae). California white oak, sometimes referred to as valley oak, is a

deciduous tree, 12 to 30 m tall, with a rounded spreading crown. The mature bark is gray, scaly, and often vertically fissured in a checker-like pattern. Leaves are oblong to obovate, 5 to 10 cm long, with 7 to 11 deep lobes. The upper surface is green and shiny; the lower surface is grayish green. Like all oaks, white oak is monoecious and wind-pollinated. The acorn cups are composed of thick, tubercled scales. The one-seeded nuts are 3 to 5 cm long, oblong to ovoid, and mature in one year. Flowering takes place from March to April. Fruits mature between August and October. Good acorn production has been reported to occur annually, but high acorn numbers occur episodically. Trees of this species may be among the largest oaks in North America.