Western Poison Oak, Pacific poison oak

Rhus diversiloba

Physical Characteristics

Rhus diversiloba is a deciduous Shrub growing to 2.5 m (8ft 2in). See above for USDA hardiness. It is hardy to UK zone 5 and is not frost tender. The species is dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required). and is pollinated by Bees. The plant is not self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers moist soil.

Distribution

Western N. America - Vancouver to California.

Habitats

Woodland Garden Sunny Edge;

Edible Uses

Edible Parts: Oil Edible Uses: Oil None known

Medicinal Uses

Antidote Contraceptive Eczema Ophthalmic Warts Western poison oak was employed medicinally by some native North American Indian tribes who used it to treat various complaints[257]. 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[257]. A tincture of the fresh leaves has been used in the treatment of eczema and skin diseases[4]. It is also used in the treatment of warts, ringworm etc[92]. A poultice of the fresh leaves has been applied to rattlesnake bites[257]. The leaf buds have been eaten in the spring in order to obtain immunity from the plant poisons[257] A moxa of the plant has been used in the treatment of warts and ringworm[257]. The juice of the plant has been used as a treatment for warts[257]. An infusion of the dried roots has been taken in order to give immunity against any further poisoning[257]. A decoction of the roots has been used as drops in the eyes to heal tiny sores inside the eyelids and to improve vision[257].

Known Hazards

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[274].