Herb: Western Poison Oak

Latin name: Rhus diversiloba

Synonyms: Toxicodendron diversilobum

Family: Anacardiaceae (Cashew Family, Sumac Family)

Medicinal use of Western Poison Oak:

Western poison oak was employed medicinally by some native North American Indian tribes who used it to treat various complaints. In view of the potential toxicity of the plant, extreme caution is advised in any use of it. See the notes above on toxicity. A leaf has been swallowed in the spring as a contraceptive. A tincture of the fresh leaves has been used in the treatment of eczema and skin diseases. It is also used in the treatment of warts, ringworm etc. A poultice of the fresh leaves has been applied to rattlesnake bites. The leaf buds have been eaten in the spring in order to obtain immunity from the plant poisons A moxa of the plant has been used in the treatment of warts and ringworm. The juice of the plant has been used as a treatment for warts. An infusion of the dried roots has been taken in order to give immunity against any further poisoning. A decoction of the roots has been used as drops in the eyes to heal tiny sores inside the eyelids and to improve vision.

Description of the plant:


2.5 m
(8 1/4 foot)

Habitat of the herb:

Thickets and wooded slopes in foothills, along streams, in washes and hedgerows below 1500 metres.

Other uses of Western Poison Oak:

The leaves are rich in tannin. They can be collected as they fall in the autumn and used as a brown dye or as a mordant. An oil is extracted from the seeds. It attains a tallow-like consistency on standing and is used to make candles. These burn brilliantly, though they emit a pungent smoke. The supple stems are used as the warp in basket making. Slender stems are used as circular withes in basket making. An excellent black dye is obtained by exposing the sap to air.

Propagation of the herb:

Seed - best sown in a cold frame as soon as it is ripe. Pre-soak the seed for 24 hours in hot water (starting at a temperature of 80 - 90c and allowing it to cool) prior to sowing in order to leach out any germination inhibitors. The stored seed also needs hot water treatment and can be sown in early spring in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Cuttings of half-ripe wood, 10cm with a heel, July/August in a frame. Root cuttings 4cm long taken in December and potted up vertically in a greenhouse. Good percentage. Suckers in late autumn to winter.

Cultivation of Western Poison Oak:

Thickets and wooded slopes in foothills, along streams, in washes and hedgerows below 1500 metres.

Known hazards of Rhus diversiloba:

All parts of the plant contain resinous phenolic compounds known as urushiols. Direct contacr with the plant, exposure to smoke or fumes from a burning plant or even contact with pets or animals that have touched the plant can cause severe allergic dermatitis in some individuals. There is usually a latent period of about 12 - 24 hours from the moment of contact, this is followed by a reddening and severe blistering of the skin. Even plant specimens 100 or more years old can cause problems.

Plant information taken from the Plants For A Future.