blue oak Fagaceae Quercus
douglasii Hook. & Arn. symbol: QUDO
Leaf: Alternate, simple, and usually deciduous (although trees on moist sites may retain their leaves); 1 to 3 inches long; margins are usually wavy, but are sometimes shallowly and irregularly lobed; the upper side of the leaf is distinctly bluish-green, especially later in the growing season, while the lower surface is pale green.
Flower: Species is monoecious; males are borne in pendent yellow-green catkins (aments); females are small, often solitary, and occur in the axils of leaves on current year's twigs; appearing in spring.
Fruit: Acorns; oval to gently tapering; 3/4 to 1 1/2 inches long; shallow caps with warty scales; ripen in a single year.
Twig: Stout, brittle, and gray to reddish brown.
Bark: Mature bark is light gray and checkered.
Form: A small to medium sized deciduous tree; seldom more than 60 feet tall and 2 feet in diameter. Open grown canopies are typically rounded with many crooked branches.
Looks like: canyon live oak - valley oak - Oregon white oak - tanoak
Additional Range Information: Quercus douglasii is native to North America. Range may be expanded by planting. See states reporting blue oak.
External Links: USDAFS Silvics of North America - USDAFS Additional Silvics - USDA Plants Database
All material © 2017 Virginia Tech Dept. of Forest Resources and Environmental Conservation; Photos and text by: John Seiler, Edward Jensen, Alex Niemiera, and John Peterson