Toxicodendron diversilobum (Pacific poison oak)

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Toxicodendron, Genus, diversilobum, Species,

Genus & species

Pacific poison oak

Anacardiaceae Western North America

Attracts Pollinators Drought Tolerant

SunFull Sun – Part Shade – Full Shade

WaterLow · drought-tolerant

HardinessZones 7–10

Overview

Toxicodendron diversilobum is a deciduous woody plant in the cashew family that grows either as an upright shrub 3-6 feet (1-2 m) tall or as a climbing vine reaching 13-20 feet (4-6 m) or more into supporting trees. Its leaves are divided into three leaflets, each 1-4 inches (2.5-10 cm) long with scalloped or lobed margins resembling those of an oak. New foliage emerges glossy bronze-red, matures to green, and turns red and orange in autumn before dropping. Clusters of small greenish-white flowers appear in spring, followed by white to tan berry-like drupes. All parts contain urushiol, an oily compound that causes allergic contact dermatitis in most people, with a blistering, itching rash developing one to several days after contact; the oil stays active on tools, clothing, and pet fur, and smoke from burning plants can affect the lungs. The species is native to western North America, where it forms thickets in chaparral, oak woodland, and forest edges, and bears berries and foliage eaten by birds and mammals that are unaffected by the urushiol. It tolerates sun or shade and a wide range of soils, and spreads by both seed and creeping rhizomes.

Native Range

Native to western North America, from British Columbia south through California to Baja California, and east into Nevada. It grows in chaparral, oak woodlands, coniferous forests, and along streams from sea level to moderate mountain elevations.

Suggested Uses

Not used in cultivation. In its native range it stabilizes slopes and supplies cover and berries for wildlife within chaparral and woodland. Its bronze spring growth and red autumn color are conspicuous in wild landscapes.

How to Identify

Identified by leaves divided into three lobed leaflets, the source of the saying leaves of three, let it be. New growth is glossy bronze-red, and autumn foliage turns bright red and orange. It grows as a low shrub or as a woody vine climbing tree trunks, and bears loose clusters of small white-green flowers and whitish drupes.

Appearance

Size & Dimensions

Height3' - 13'

Width/Spread3' - 10'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

red

orange

Bloom Information

Bloom Period

~4 weeks

Flowers: April–May

Spring

Flowers in spring, generally April and May, producing loose clusters of tiny greenish-white blossoms among the new leaves. Bees and other insects visit the flowers. Pale berry-like drupes form by late summer and can persist on bare stems into winter.

Detailed Descriptions

Foliage Description

Green, bronze-red when young, turning red and orange in autumn

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade SunFull Shade

Requires 3-8 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 - 7.5 (Acidic to alkaline)

3579

Soil Types

loam sand clay rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Highly adaptable, growing in full sun to deep shade and in soils ranging from sand to clay with a pH of about 5.0 to 7.5. Drought tolerant once established, drawing on deep roots through dry summers. It spreads by seed and by rhizomes, forming dense thickets, and resprouts after cutting or fire. It is almost never grown intentionally because contact with any part causes an allergic rash in most people. Removal is difficult since the urushiol oil persists on cut stems and tools.

Pruning

Pruning is generally avoided because cut stems, leaves, and roots all carry urushiol that causes skin reactions. Where plants are taken out, the oil stays active on tools and gloves for long periods. Cutting alone rarely kills the plant, which resprouts strongly from roots and rhizomes.