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Rhus diversiloba
| Common name: |
Western Poison Oak |
Family: |
Anacardiaceae |
| Author: |
Torr.&A.Gray. |
Botanical references: |
11, 71, 200 |
| Synonyms: |
Toxicodendron diversilobum ((Torr.&A.Gray.)Greene.) |
| 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]. |
| Range: |
Western N. America - Vancouver to California. |
| Habitat: |
Thickets and wooded slopes in foothills, along streams, in washes and hedgerows below 1500 metres[71, 92]. |
| Edibility Rating (1-5): |
0 | Medicinal Rating (1-5): | 2 |
| Other Possible Synonyms: | From various places across the web, may not be correct. See below. |
| R. diversilobe[H]
Toxicodendron radicans ssp. diversilobum[B,P]
|
| Other Common Names: | From various places around the Web, may not be correct. See below. |
| Californian Poison Oak [H], Ma Tu Ya Ho [E], Pacific Poison Oak [P], Pacific Poison-oak [B,DEN1], Poison-oak [FEIS], |
| Epithets: | From a Dictionary of Botanical Epithets |
|
diversiloba = many shaped lobes;
|
| Systematics: | From a USDA Plants Database |
|
Order: Sapindales. Sumac family
|
| Other Range Info: |
From the Ethnobotany Database |
|
Us(Pomo)
|
Physical Characteristics
A decidious shrub growing to 2.5m. It is hardy to zone 5 and is frost tender. The flowers are 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 are pollinated by Bees.
The plant not is self-fertile.
We rate it 0/5 for edibility and
2/5 for medicinal use.
The plant prefers light (sandy), medium (loamy) and heavy (clay) soils, requires well-drained soil and can grow in nutritionally poor soil.
The plant prefers acid, neutral and basic (alkaline) soils.
It cannot grow in the shade.
It requires moist soil.
Habitats and Possible Locations
Woodland, Sunny Edge.Edible Uses
None known
Medicinal Uses
Disclaimer
Antidote; Contraceptive; 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].
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[169].
An oil is extracted from the seeds[4]. It attains a tallow-like consistency
on standing and is used to make candles. These burn brilliantly, though they
emit a pungent smoke[4].
The supple stems are used as the warp in basket making[92]. Slender stems
are used as circular withes in basket making[257].
An excellent black dye is obtained by exposing the sap to air[92].
Cultivation details
Succeeds in a well-drained fertile soil in full sun[200]. Plants do not
require a rich soil[11].
The young growth in spring can be damaged by late frosts.
Plants have brittle branches and these can be broken off in strong
winds[200]. Plants are also susceptible to coral spot fungus[11].
This species is closely related to R. toxicodendron[1].
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[1, 4]. The toxic species are sometimes separated into
their own genus, Toxicodendron, by some botanists[200].
Plants in this genus are notably resistant to honey fungus[200].
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[200]. The stored seed also needs hot water treatment and can be
sown in early spring in a cold frame[200]. 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[200].
Root cuttings 4cm long taken in December and potted up vertically in a
greenhouse. Good percentage[78, 200].
Suckers in late autumn to winter[200].
Suppliers
For more details of plant suppliers please see our Suppliers Page which lists many more places to look.
Web References
- Details of Medicinal Uses, Habitats, etc. in M. Grieve A Modern Herbal (1931) [4]
- [E] Ethnobotany Data
(common names, uses, countries) from the Ethnobotany Database.
- [G] Data
(Common Names, Uses, Distribution) from the USDA/ARS NPGS's GRIN taxonomic database.
- [P] Data.
(uses, distribution, wetland) from the USDA'a Plants database.
- [HP] Links, Photos, Suppliers from Hortiplex Plant Database
References for Rhus diversilobe (a possible synonym).
- [H] Details of Scandanavian and European Common names in Henriette's names database
References for Toxicodendron diversilobum (a possible synonym).
- [B] Data
(Latin & Common names, other references) from the BONAP's Synonymized Checklist of the Vascular Flora of the United States, Puerto Rico, and the Virgin Islands.
- [G] Data
(Common Names, Uses, Distribution) from the USDA/ARS NPGS's GRIN taxonomic database.
- [C] Taxon data.
from the CalFlora database.
- Images
from the CalPhoto database.
- [P] Data.
(uses, distribution, wetland) from the USDA'a Plants database.
- [FEIS] Data
(Uses, Ecology, Fire Effects) from the USDA Forestry Service Fire Effects Information System.
- [DEN] Data _ Photos
(Good Identification info) from the Virginia Tech's Dendrology Deptarments' Tree Fact Sheets.
- [FEIS] Data
(Uses, Ecology, Fire Effects) from the USDA Forestry Service Fire Effects Information System.
References for the family Anacardiaceae.
See the PFAF Links Pages for other sources.
Also try Photos and info from the The Plants Database which has 14,000 images.
[1] F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press 1951
Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaces in 1992 by a new dictionary (see [200]).
[4] Grieve. A Modern Herbal. Penguin 1984 ISBN 0-14-046-440-9
Not so modern (1930's?) but lots of information, mainly temperate plants.
[11] Bean. W. Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. Murray 1981
A classic with a wealth of information on the plants, but poor on pictures.
[71] Munz. A California Flora. University of California Press 1959
An excellent flora but no pictures. Not for the casual reader.
[78] Sheat. W. G. Propagation of Trees, Shrubs and Conifers. MacMillan and Co 1948
A bit dated but a good book on propagation techniques with specific details for a wide range of plants.
[92] Balls. E. K. Early Uses of Californian Plants. University of California Press 1975 ISBN 0-520-00072-2
A nice readable book.
[169] Buchanan. R. A Weavers Garden.
Covers all aspects of growing your own clothes, from fibre plants to dyes.
[200] Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992 ISBN 0-333-47494-5
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
[257] Moerman. D. Native American Ethnobotany Timber Press. Oregon. 1998 ISBN 0-88192-453-9
Very comprehensive but terse guide to the native uses of plants. Excellent bibliography, fully referenced to each plant, giving a pathway to further information. Not for the casual reader.
Readers Comments
Main Search Page
Bibliography
Plant information taken from the
Plants For A Future -
Species Database.
Copyright (c) 1997-2003.
WEB search engine by Rich Morris - Home Page- Contact Info
Blagdon Cross, Ashwater, Beaworthy, Devon, EX21 5DF, UK.
Website: www.pfaf.org Phone: 0845 458 4719/_44(0) 1208 872963 This page (UK) http://www.comp.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhus+diversiloba
This page (US) http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Rhus+diversiloba
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