Toxicodendron diversilobum
Toxicodendron diversilobum Pacific poison oak | |
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Pacific poison oak (larger and reddish leaves) at the base of an oak tree | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Rosids |
Order: | Sapindales |
Family: | Anacardiaceae |
Genus: | Toxicodendron |
Species: | T. diversilobum
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Binomial name | |
Toxicodendron diversilobum | |
Synonyms | |
Rhus diversiloba Torr. & A.Gray |
Toxicodendron diversilobum (syn. Rhus diversiloba), commonly named Pacific poison oak[1] or western poison oak, is a woody vine or shrub in the sumac family, Anacardiaceae. It is widely distributed in western North America, inhabiting conifer and mixed broadleaf forests, woodlands, grasslands, and chaparral biomes.[2] Peak flowering occurs in May.[3] Like other members of the genus Toxicodendron, T. diversilobum causes itching and allergic rashes in most people after contact by touch or smoke inhalation. Despite its name, it is not closely related to oaks, nor is it a true tree.
Description
Toxicodendron diversilobum is extremely variable in growth habit and leaf appearance. It grows as a dense 0.5–4 metres (1+1⁄2–13 feet) tall shrub in open sunlight, a treelike vine 3–9 m (10–30 ft) and may be more than 30 m (100 ft) long with an 8–20 centimetres (3+1⁄4–7+3⁄4 inches) trunk, as dense thickets in shaded areas, or any form in between.[4][5] It reproduces by spreading rhizomes and by seeds.[2]
The plant is winter deciduous, so that after cold weather sets in, the stems are leafless and bear only the occasional cluster of mature fruit. 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 cm (1+1⁄2 to 4 in) long, with scalloped, toothed, or lobed edges.[6] 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.[4]
White flowers form in the spring, from March to June.
Botanist John Howell observed that the plant's toxicity obscures its aesthetic values:
- 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.[7]
Distribution and habitat
Toxicodendron diversilobum is found in
Toxicodendron diversilobum is common in various habitats, from mesic
Ecology
Black-tailed deer, mule deer, California ground squirrels, western gray squirrels, and other indigenous fauna feed on the leaves of the plant.[4] It is rich in phosphorus, calcium, and sulfur.[4] Bird species use the berries for food, and utilize the plant structure for shelter.[4] Neither native animals nor horses, livestock, or dogs demonstrate reactions to urushiol.[2]
Due to human allergic reactions, T. diversilobum is usually eradicated from gardens and public landscaped areas. It can be a weed in agricultural fields, orchards, and vineyards.[11] It is usually removed by pruning, herbicides, digging out, or a combination.[12] Poison oak is susceptible to infection by Phytophthora ramorum.[13]
Toxicity
Toxicodendron diversilobum leaves and twigs have a surface oil, urushiol, which causes an allergic reaction.[2] It causes contact dermatitis – an immune-mediated skin inflammation – in four-fifths of humans.[14][15] Most, if not all, will become sensitized over time with repeated or more concentrated exposure to urushiol.
The active components of urushiol have been determined to be unsaturated congeners of 3-heptadecylcatechol with up to three double bonds in an unbranched C17 side chain.[16] In poison ivy, these components are unique in that they contain a -CH2CH2- group in an unbranched alkyl side chain.[17]
Exposure
Toxicodendron diversilobum skin contact first causes itching; then evolves into dermatitis with inflammation, colorless bumps, severe itching, and blistering.[18] In the dormant deciduous seasons the plant can be difficult to recognize, however contact with leafless branches and twigs also causes allergic reactions.
Urushiol volatilizes when burned, and human exposure to T. diversilobum smoke is extremely hazardous, from wildfires, controlled burns, or disposal fires.[4] The smoke can poison people who thought they were immune.[4] Branches used to toast food over campfires can cause reactions internally and externally.
Urushiol is also found in the skin of
Uses
Medicinal
An infusion of dried roots, or buds eaten in the spring, were taken by some native peoples for an immunity from the plant poisons.[21]
Chumash peoples used T. diversilobum sap to remove warts, corns, and calluses; to cauterize sores; and to stop bleeding.[21] They drank a decoction made from the roots to treat dysentery.[23]
Cultivation
Toxicodendron diversilobum can be a carefully situated component in
The plant is used in
See also
- Toxicodendron vernix – poison sumac
- Toxicodendron radicans – eastern poison ivy
References
- ^ USDA, NRCS (n.d.). "Toxicodendron diversilobum". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 11 December 2015.
- ^ a b c d C. Michael Hogan (2008); "Western poison-oak: Toxicodendron diversilobum" Archived 2009-07-21 at the Wayback Machine, GlobalTwitcher, ed. Nicklas Strömberg
- ^ iNaturalist: Toxicodendron diversilobum
- ^ a b c d e f g h i j k l U.S. Forest Service: Toxicodendron diversilobum
- ^ Integrated Taxonomic Information System (ITIS): Toxicodendron diversilobum (Western Poison-oak) - Overview
- ^ a b c Jepson
- ISBN 978-0940228702.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - ^ Roots of native names, by Ron Sullivan, in the San Francisco Chronicle; published December 7, 2002; retrieved June 20, 2017
- ^ USDA, NRCS (n.d.). "Toxicodendron diversilobum". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 2013-09-20.
- ^ Calflora
- ^ UC Integrated Pest Management Weed Photo Gallery and information (profile of this plant as an agricultural weed).
- ^ Sunset Western Garden Book [5th edition], (Menlo Park: Sunset Publishing, 1988), p. 506
- .
- PMID 7910172.
- ^ "Mic-ro.com: Contact-Poisonous Plants of the World". Archived from the original on 2010-07-02. Retrieved 2007-07-16.
- PMID 1185545.
- PMID 641754.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - ^ Poison Oak/Poison Ivy Information Center
- S2CID 31162401.
- ^ Brody, Jane E. (June 16, 2014). "Steering Clear of Poison Ivy". New York Times. Retrieved 2016-01-11.
- ^ a b c d Univ. of Michigan, Dearborn – Native American Ethnobotany Database: Toxicodendron diversilobum
- . PSW-99.
- S2CID 25807034.
Gallery
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Red phase in spring
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Green phase, and flowers
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Berries
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Summer–autumn turning color phase
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Shrub form
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Vine form
External links
- U.S. Forest Service information: Toxicodendron diversilobum (Pacific poison oak)
- Calflora Database: Toxicodendron diversilobum (Pacific poison oak)
- Jepson Flora Project: Toxicodendron diversilobum
- American Academy of Dermatology – Poison Oak information
- Toxicodendron diversilobum – U.C. Photo gallery