Toxicodendron radicans

Poison-ivy

Anacardiaceae

The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta(FLowering plants). Class - Magnoliopsida. Order - Sapindales. Family - Anacardiaceae (Sumac family). Genus -Toxicodendron Mill. Species - Toxicodendren radicans (L.) Kuntze.

Ecology: Poison-ivies occur in a variety of plant communities from barrier-island sand dunes to subalpine sites. They occur primarily in wetlands, floodplains, bottomlands, and riparian communities throughout their ranges, but they also occur frequently in upland hardwood, mixed hardwood-conifer, and conifer forests and woodlands. In forests, they often occur in canopy gaps and on edges. They also occur in prairies and other grasslands as well as on rocky fields, talus slopes, and cliffs.

Identification

General: Deciduous shrub 1-2 m tall or woody climbing vine up to 15 m tall, glabrous to hairy, exuding milky juice when cut.

Leaves: Leaflets 3-5, rounded, obtuse or sometimes sharp-pointed at the tips, 3-7 cm long, turning scarlet in autumn.

Flowers: Inflorescence in loose, axillary, often reflexed panicles; flowers bisexual or unisexual, 1-2 mm long, yellowish-green; stamens exserted.

Fruits: Berrylike drupes, 5 mm long, white, glabrous.

Notes: Many people develop an itching or burning rash after contacting this plant because of its slightly volatile oil.

Threats

Immediate fire effect on plant: The aboveground portions of poison-ivies are probably easily killed by fire. However, poison-ivies may sprout from rhizomes or root crowns that are protected from fire by soil.

Plant response to fire: Poison-ivies sprout from the root crown and/or from rhizomes after top-kill by fire

Reproduction

Pollination and breeding system: Poison-ivies are dioecious [88,124,171]. Their flowers are not specialized for any particular pollinator type. They are visited and pollinated by ants, bees, beetles, butterflies, flies, true bugs, and wasps. Ants, bees, and wasps appear to be the most important pollinators.

Seed production: Because male and female flowers are on separate plants, not all poison-ivy plants bear fruit. Poison-ivy fruit and seed production is often high. Seeds of poison-ivies are dispersed by birds and mammals and sometimes by water. Fruits are eaten and dispersed by numerous birds and mammals during fall, winter, and early spring, and the hard seeds pass through their digestive tracts in viable condition.

Seedling Development - Once established, survival of poison-ivies may be high and their growth rapid.

Vegetative Reproduction - Poison-ivies sprout from root crowns and rhizomes. Plants may reproduce vegetatively in their 1st growing season. In Canada, poison-ivy plants in their 1st or 2nd growing seasons may produce rhizomes from the base of the primary vertical shoot. Rhizomes have buds that produce secondary vertical stems similar to the primary vertical stem; they usually also produce adventitious roots just below each bud. The secondary vertical stems produce further rhizomes, resulting in a large interconnected clone with many vertical stems and rhizomes above or beneath the ground.

Species Distribution

Citation

E-Flora of British Columbia
In Klinkenberg, Brian. (Editor) 2015. E-Flora BC: Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver.

USDA Plants Database
USDA, NRCS. 2017. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
Distribution Map photo credit

USFS Plant Database
Innes, Robin J. 2012. Toxicodendron radicans, T. rydbergii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer)

Jepson eFlora: Taxon Page
John M. Miller & Dieter H. Wilken 2017. Toxicodendron, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=9982, accessed on February 13, 20

Burke Museum of Natural History and Culture
Burke Museum. 2017. Toxicodendron radicans [Online]. University of Washington.
Photo credit: 2005, Ben Legler