Toxicodendron radicans, commonly known as eastern poison ivy or poison ivy, is a species of allergenic flowering plant. It has numerous subtaxons and forms both vines and shrubs. Despite its common name, it is not a true ivy, but rather a member of the cashew and sumac family, Anacardiaceae. It is different from western poison ivy, Toxicodendron rydbergii, and resembles a number of species. The species is found in North America. Although commonly eaten by animals, with birds consuming the seeds, T. radicans is considered a noxious weed. As a poison ivy, it causes urushiol-induced contact dermatitis in most people who touch it, producing an itchy, irritating, and sometimes painful rash.
Description Numerous subspecies and/or varieties of T. radicans are known. They can be found growing in any of the following forms, all having woody stems:
as a climbing vine that grows on trees or some other support as a shrub up to 1.2 metres (4 feet) tall as a trailing vine that is 10–25 centimetres (4–10 inches) long. The deciduous leaves of T. radicans are trifoliate with three almond-shaped leaflets. The leaf color ranges from light green (usually when young) to dark green (in maturity), turning red, orange or yellow in fall; some sources say the leaves are also reddish when expanding (before becoming dark green). The leaflets are 3–12 cm (1+1⁄4–4+3⁄4 in) long, rarely up to 30 cm (12 in), and somewhat shiny in maturity. Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth. Leaflet clusters are alternate on the vine, and the plant has no thorns. Vines growing on the trunk of a tree become firmly attached through numerous aerial rootlets. The vines develop adventitious roots, or the plant can spread from rhizomes or root crowns. The milky sap of poison ivy darkens after exposure to the air.
T. radicans spreads either vegetatively or sexually. It is dioecious; flowering occurs from May to July. The yellowish- or greenish-white flowers are typically inconspicuous and are located in clusters up to 8 cm (3 in) above the leaves. The berry-like fruit, a drupe, mature by August to November with a grayish-white colour.
Identification These four characteristics are sufficient to identify poison ivy in most situations: (a) clusters of three leaflets, (b) alternate leaf arrangement, (c) lack of thorns, and (d) each group of three leaflets grows on its own stem, which connects to the main vine, the middle stem is longer. The appearance of poison ivy can vary greatly among environments, and even within a large area. Identification by experienced people is often made difficult by leaf damage, the plant's leafless condition during winter, and unusual growth forms due to environmental or genetic factors. Various mnemonic rhymes describe the characteristic appearance of poison ivy:
"Leaves of three, let it be" is the best known and most useful cautionary rhyme. It applies to poison oak, as well as to poison ivy. However, some other innocuous plants have similar leaves. "Hairy vine, no friend of mine" "Berries white, run in fright" and "Berries white, danger in sight"
… excerpt ends here. Continue reading the full article.
