blue oak Fagaceae Quercus
douglasii Hook. & Arn.
|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
| Additional Range Information:
Quercus douglasii is native to North America.
Range may be expanded by planting.
See states reporting blue oak.
| External Links:
Silvics of North America
USDA Plants Database
|© Copyright 2016, Virginia Tech|
Dept. of Forest Resources
and Environmental Conservation,
all rights reserved.
Photos and text by: John Seiler,
Edward Jensen, Alex Niemiera,
and John Peterson