Notholithocarpus spp.

Tanoak

Fagaceae Pacific coast of North America

Attracts Pollinators Fragrant (moderate)

Native to North America

SunFull Sun – Part Shade

WaterMedium

HardinessZones 7–9

Overview

Notholithocarpus spp. is a genus of the beech family (Fagaceae) with a single species, Notholithocarpus densiflorus, the tanoak or tanbark-oak, of the Pacific coast of North America. It is an evergreen tree 15-40 m (50-130 ft) tall, or a low shrub at high elevations, with a dense rounded crown and thick, furrowed grey bark. The leathery leaves are 5-13 cm (2-5 in) long, oblong with coarse teeth, glossy green above and coated beneath with pale, woolly hairs that wear away with age. Erect, catkin-like spikes of small cream flowers open in summer, carrying a strong scent, with male flowers above and a few female flowers at the base. The fruit is an acorn 2-3 cm (0.8-1.2 in) long seated in a shallow cup covered in spreading, bristly scales, taking two years to ripen. Tanoak bridges the true oaks and the tropical stone-oaks in form. The bark was once a major source of tannin for tanning leather. The species is highly susceptible to sudden oak death, a disease caused by Phytophthora ramorum that has killed many trees in coastal California and Oregon.

Native Range

Notholithocarpus densiflorus is native to the Pacific coast of North America, from south-western Oregon through the Coast Ranges and Sierra Nevada foothills of California. It grows in mixed evergreen and redwood forest, on slopes and in canyons, from near sea level to mid mountain elevations. The single species is confined to this western range.

Suggested Uses

Grown as a shade and specimen tree in large gardens and in restoration of west-coast mixed evergreen forest, spaced well apart for the broad crown. The acorns feed many birds and mammals. Its disease susceptibility limits planting where sudden oak death is established.

How to Identify

Look for an evergreen tree with thick leathery, coarsely toothed oblong leaves that are glossy above and woolly-pale beneath when young. Erect, strongly scented cream catkins appear in summer, unlike the drooping catkins of true oaks. Acorns sit in shallow cups covered with spreading bristly scales, a feature that identifies Notholithocarpus spp..

Appearance

Size & Dimensions

Height50' - 130'

Width/Spread30' - 60'

Colors

Flower Colors

white

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~4 weeks

Summer

Erect cream catkin-like spikes open in summer, mainly June to August, releasing a strong scent. Male flowers crowd the upper spike with a few female flowers at the base. Acorns develop slowly and take two years to ripen, so green and mature acorns can appear together.

Detailed Descriptions

Foliage Description

Glossy green above, pale woolly beneath

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-8 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 6.5(Acidic)

357912

Soil Types

loam sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

20+ years

Care & Maintenance

Care Guide

Notholithocarpus spp. grows in full sun to part shade on deep, moist, free-draining acidic soils with a pH near 5.0 to 6.5. It suits cool, mild coastal and montane climates in roughly USDA zones 7 to 9 and resents heat, drought, and alkaline ground. Young trees establish slowly and need steady moisture for the first few years. The species is highly vulnerable to sudden oak death, so its use is limited where Phytophthora ramorum is present. Good air movement and dry foliage reduce disease pressure. Mature trees need little routine care in a suitable climate.

Pruning

Little pruning is needed beyond removing dead, damaged, or diseased wood, done in dry summer weather to limit disease entry. The dense crown forms naturally and responds slowly to cutting. Lower branches can be raised on young trees for clearance.