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   » » Wiki: Toxicodendron
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Toxicodendron is a genus of in the family, . It contains , and , including , , and the . All members of the genus produce the skin-irritating oil , which can cause a severe reaction. The generic name is derived from the words ( toxikos), meaning "poison," and ( dendron), meaning "tree". ξ1 The best known members of the genus in are poison ivy (T. radicans), practically ubiquitous throughout most of eastern North America, and western poison oak ( ), similarly ubiquitous throughout much of the western part of the continent.

The genus is a member of the complex, and has at various times been categorized as being either its own genus or a sub-genus of Rhus., page 89 There is evidence which points to keeping Toxicodendron as a separate genus, but researchers have stated that the Toxicodendron and Rhus groups are complex and require more study to be fully understood.http://onlinelibrary.wiley.com/doi/10.1111/j.1759-6831.2009.00045.x/full

Plants in the genus have compound, alternate leaves and whitish or grayish . They are quite variable in appearance. The leaves may have smooth, toothed or lobed edges, and all three types of leaf edge may be present in a single plant. The plants grow as creeping vines, climbing vines, shrubs, or, in the case of lacquer tree ( ) and poison sumac ( ), as trees. While leaves of poison ivy and poison oaks usually have three leaflets, sometimes there are five or, occasionally, even seven leaflets. Leaves of poison sumac have 7–13 leaflets, and of Lacquer Tree, 7–19 leaflets.

The common names come from similar appearances to other species that are not closely related and to the allergic response to the urushiol. Poison oak is not an ( Quercus, family ), but this common name comes from the leaves' resemblance to white oak ( ) leaves, while poison ivy is not an ( Hedera, family ), but has a superficially similar growth form. Technically, the plants do not contain a ; they contain a potent .

The of certain species native to , and other , such as lacquer tree ( T. vernicifluum) and wax tree ( ), are used to make , and, as a of lacquer , their berries are used to make .


Avoidance, treatment, and safety
For specific information on prevention and treatment of Toxicodendron rashes, see .


Selected species of Toxicodendron

  • Western poison oak ( or Rhus diversiloba) is found throughout much of western , ranging from the into the and between southern and southward into . It is extremely common in that region, where it is the predominant species of the genus. Indeed, it is California's most prevalent woody shrub. Extremely variable, it grows as a dense shrub in open sunlight, or as a climbing vine in shaded areas. It propagates by creeping or by seed.C.Michael Hogan (2008) Western poison-oak: Toxicodendron diversilobum, GlobalTwitcher, ed. Nicklas Stromberg [1] The compound leaves are divided into three leaflets, 35–100 mm long, with scalloped, toothed, or lobed edges. Californians learn to recognize it by the rhyme "leaves of three, let it be". The leaves may be red, yellow, green, or some combination of those colors, depending on various factors, such as the time of year.

  • Asian poison ivy ( , Rhus orientale or R. ambigua) is very similar to the American poison ivy, and replaces it throughout east Asia (so similar that some texts treat it as just a variety of the American species).

  • Potanin's lacquer tree or Chinese varnish tree ( or Rhus potaninii) from central China, is similar to T. vernicifluum but with (usually) fewer leaflets per leaf. Growing up to 20 m tall, like T. vernicifluum it is used for production. The leaves have 7–9 leaflets.

  • Atlantic poison oak ( or Rhus toxicarium) grows mostly in sandy soils in eastern parts of the United States. Growing as a shrub, its leaves are in groups of three. Leaves are typically rounded or lobed, and are densely haired. Although it is often confused with the more common poison ivy, even in the scientific literature, Atlantic Poison oak has small clumps of hair on the veins on the underside of the leaves, while Poison ivy does not.

  • Poison ivy ( or Rhus radicans) is extremely common in some areas of North America. In the United States it grows in all states east of the Rockies except North Dakota. It also grows in Central America. Appearing as a creeping vine, a climbing vine, or a shrub, it reproduces both by creeping rootstocks and by seeds. The appearance varies. Leaves, arranged in an alternate pattern, usually in groups of three, are from 20 to 50 mm long, pointed at the tip, and may be toothed, smooth, or lobed, but never serrated. Leaves may be shiny or dull, and the color varies with the season. Vines grow almost straight up rather than wrapping around their support, and can grow to 8–10 m in height. In some cases, Poison ivy may entirely engulf the supporting structure, and vines may extend outward like limbs, so that it appears to be a Poison ivy "tree".

  • Western poison ivy ( or Rhus rydbergii) is found in northern parts of the eastern United States. It also exists in the western United States and Canada, but is much less common than poison oak. It may grow as a vine or a shrub. It was once considered a subspecies of poison ivy. It does sometimes hybridize with the climbing species. Western poison ivy is found in much of western and central United States and Canada, although not on the West Coast. In the eastern United States it is rarely found south of New England.

  • Wax tree ( or Rhus succedanea), a native of Asia, although it has been planted elsewhere, most notably Australia and New Zealand. It is a large shrub or tree, up to 8 m tall, somewhat similar to a sumac tree. Because of its beautiful autumn foliage, it has been planted outside of Asia as an , often by gardeners who were apparently unaware of the dangers of allergic reactions. It is now officially classified as a noxious weed in Australia and New Zealand. The fatty-acid methyl ester of the kernel oil meets all of the major requirements in the USA (ASTM D 6751-02, ASTM PS 121-99), Germany (DIN V 51606) and European Union (EN 14214).http://dx.doi.org/10.1016/j.biombioe.2005.05.001

  • Lacquer tree or varnish tree ( or Rhus verniciflua) grows in Asia, especially China and Japan. Growing up to 20 m tall, its sap produces an extremely durable . The leaves have 7–19 leaflets (most often 11–13). The sap contains the allergenic oil, urushiol. Urushiol gets its name from this species which in is called Urushi. Other names for this species include Japanese lacquer tree, Japanese Varnish Tree and Japanese Sumac (Note: the term "varnish tree" is also occasionally applied to the , Aleurites moluccana, a southeast Asian tree unrelated to Toxicodendron).

  • Poison sumac ( or Rhus vernix) is a tall shrub or a small tree, from 2–7 m tall. It is found in swampy, open areas and reproduces by seeds. The leaves have between 7–13 untoothed leaflets, in a arrangement. ξ2 In terms of its potential to cause , poison sumac is far more virulent than other Toxicodendron species, even more virulent than poison ivy and poison oak. According to some botanists, T. vernix is the most plant species in the United States (Frankel, 1991).


Notes

  • Frankel, Edward, Ph.D. 1991. Poison Ivy, Poison Oak, Poison Sumac and Their Relatives; Pistachios, Mangoes and Cashews. The Boxwood Press. Pacific Grove, Calif. ISBN 0-940168-18-9.


External links


References
    ^ (2018). 9780521866453, Cambridge University Press. .
    ^ (1998). 9780395904558

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