Tag: Southern California

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Botanical Name : Rhus diversiloba
Family: Anacardiaceae
Genus: Toxicodendron
Species: T. diversilobum
Kingdom: Plantae
Order: Sapindales

Synonyms:Toxicodendron diversilobum. (Torr.&Gray.)Greene, Rhus diversiloba Torr. & A.Gray

Common Names: Western Poison Oak, Pacific poison oak

Habitat : Rhus diversiloba is native to western North America – Vancouver to California. Thickets and wooded slopes in foothills, along streams, in washes and hedgerows below 1500 metres.
Description:
Rhus diversiloba is extremely variable in growth habit and leaf appearance. It grows as a dense 0.5–4 m (1.6–13.1 ft) tall shrub in open sunlight, a treelike vine 10–30 feet (3.0–9.1 m) and may be more than 100 feet (30 m) long with an 8–20 cm (3.1–7.9 in) trunk, as dense thickets in shaded areas, or any form in between It reproduces by spreading rhizomes and by seeds.

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The plant is winter deciduous, so that after cold weather sets in, the stems are leafless and bear only the occasional cluster of berries. Without leaves the stems may sometimes be identified by occasional black marks where its milky sap may have oozed and dried.

The leaves are divided into three (rarely 5, 7, or 9) leaflets, 3.5 to 10 centimetres (1.4 to 3.9 in) long, with scalloped, toothed, or lobed edges. They generally resemble the lobed leaves of a true oak, though tend to be more glossy. Leaves are typically bronze when first unfolding in February to March, bright green in the spring, yellow-green to reddish in the summer, and bright red or pink from late July to October.

White flowers form in the spring, from March to June. If they are fertilized, they develop into greenish-white or tan berries.

Botanist John Howell observed that the toxicity of T. diversilobum obscures its merits:

“In spring, the ivory flowers bloom on the sunny hill or in sheltered glade, in summer its fine green leaves contrast refreshingly with dried and tawny grassland, in autumn its colors flame more brilliantly than in any other native, but one great fault, its poisonous juice, nullifies its every other virtue and renders this beautiful shrub the most disparaged of all within our region.

Cultivation:
Succeeds in a well-drained fertile soil in full sun. Plants do not require a rich soil. The young growth in spring can be damaged by late frosts. Plants have brittle branches and these can be broken off in strong winds. Plants are also susceptible to coral spot fungus. This species is closely related to R. toxicodendron. Many of the species in this genus, including this one, are highly toxic and can also cause severe irritation to the skin of some people, whilst other species are not poisonous. It is relatively simple to distinguish which is which, the poisonous species have axillary panicles and smooth fruits whilst non-poisonous species have compound terminal panicles and fruits covered with acid crimson hairs. The toxic species are sometimes separated into their own genus, Toxicodendron, by some botanists. Plants in this genus are notably resistant to honey fungus. Dioecious. Male and female plants must be grown if seed is required.

Propagation:
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

Medicinal Uses:
Californian Native Americans used the plant’s stems and shoots to make baskets, the sap to cure ringworm, and as a poultice of fresh leaves applied to rattlesnake bites. The juice or soot was used as a black dye for sedge basket elements, tattoos, and skin darkening.

An infusion of dried roots, or buds eaten in the spring, were taken by some native peoples for an immunity from the plant poisons.

Chumash peoples used T. diversilobum sap to remove warts, corns, and calluses; to cauterize sores; and to stop bleeding. They drank a decoction made from the roots to treat dysenter

In view of the potential toxicity of the plant, extreme caution is advised in any use of it. See the notes below 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.

Other Uses:
Basketry; Dye; Ink; Mordant; Oil.

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

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

Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider.
Resources:
https://en.wikipedia.org/wiki/Toxicodendron_diversilobum
http://www.pfaf.org/user/Plant.aspx?LatinName=Rhus+diversiloba

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