Blue Oak
 

Mature Size, Growth, Longevity

A medium sized tree in landscapes, 30-50' tall and wide, with a compact crown. May reach up to 75-100' tall and 50-80' wide after many years in the wild under ideal conditions in California. Slow growth rate, only 4-12" per year. Long-lived, to about 200-300 years.

Native Range

U.S. Native — Native and endemic to California, on dry slopes, in foothills and on low mountain slopes. Found native in Central and Southern California, from Los Angeles to Sacramento.

Flower and Fruit Details

Monoecious flowers in the spring, with male catkins. Fruits (acorns) mature in one year. Acorn sits in a shallow cup (cap), and is sessile, or nearly so. Long, narrow, pointed acorns are green, then yellowish-brown to chestnut brown, 0.8-1.5" long. Kernel is sweet. Valued by wildlife and livestock.

Leaf and Bark Features

Deciduous: A white oak type, with 1-4" leaves pinnate-lobed (3-5 pairs of lobes), oblong/ovate, dark blue-green/blue-gray above, pale/hairy below. Leaves variable, spiny dentate to entire margined to wavy to shallowly lobed, w/ generally rounded lobes & sinuses. Fall color bronze/gold/orange/green (one or more colors at once). Develops thick bark, 0.5-1" thick. Bark is light-colored, smooth, scaly, or furrowed, gray to brown. Young twigs are stout, reddish-brown.

Culture and Care

Tolerates clay, loam or sandy soil, pH 6-8. Zones 6-9. Needs full sun to medium shade. Takes moist or dry soil. Resistant to Verticillium wilt. Susceptible to caterpillars, insect galls, scale and powdery mildew.

Strengths, Weaknesses, Other Facts

Strong branches. Somewhat resistant to soil compaction. Good wildlife value. 3-season interest: Spring, summer and fall. This tree is a common host for the Spanish Moss in California. Extensive handling of acorns may cause minor dermatitis in some individuals.

Suggested Uses

Shade tree, or use young plants for bonsai.

Taxa and Plants of this Species at BCA