Notholithocarpus densiflorus

Common Names

Tanoak, Tanbark-Oak, Tanbark Oak, Tan Oak

Summary

Tan oak, tanoak, is an evergreen broadleaf tree native to southern Oregon through California, occurring as a shrub or tree with a crown ranging from narrow-conical to broad; leaves are thick, leathery, 8–13 cm long with teeth, and new growth bears orange-brown hairs; flowers are inconspicuous catkins with white blossoms in spring; fruit is an acorn 2–3 cm long that ripens over two years, with a spiny cup; bark is fissured gray to brown; it is one of the few evergreen broad-leaved trees in the Willamette Valley.

Grows best in sun to partial shade with evenly moist, well-drained soils, is adaptable to a range of moisture conditions, and is drought-tolerant once established; hardy to USDA zones 6a–10b; bark tannin-rich and historically used for tanbark; acorns and leaves support wildlife, while the tree provides timber potential and landscape value in appropriate settings.

Lifecycle

Perennial

Height

49-131 feet

Spread

18-51 inches

Hardiness Zones

Zones 7a-8b

Sunlight Requirements

Ideally full sun to partial shade.

Soil Type

Deep, well-drained soil with high organic content

Soil Drainage

Well-drained

Soil pH

5.1-7.5, mildly acidic, neutral to mildly alkaline soils

Bloom Color

White

Bloom Time

Spring

Foliage Color

Green

Fall Foliage Color

No fall color; evergreen

Leaf Lifecycle

Evergreen broadleaf

Growth Rate

Slow

Seasons of Interest

Spring, Summer, Fall, Winter

Propagation Methods

Seeds, Cuttings, Burl-sprout vegetative regeneration (sprouts)

Attracts Wildlife

Attracts birds, including acorn woodpeckers, Steller's jay, varied thrush, and band-tailed pigeons