Toronto
Master Gardener Factsheet 
Toronto Master Gardeners are trained volunteers dedicated to providing horticultural information to the public.
For answers to horticultural questions contact the Toronto Master Gardeners' Info Line at the Toronto Botanical Garden (416) 397-1345 (Mon. to Fri. 10 a.m. to 1 p.m and Sat., Sun. and Holidays noon to 3 p.m.) or our web site.
Links
 |
 |
 |
 |
 |
Toronto Botanical Garden is a volunteer-based, charitable organization whose purpose is to inspire passion, respect and understanding of gardening, horticulture, the natural landscape and a healthy environment.
777 Lawrence Avenue East
Toronto, ON M3C 1P2
Tel. 416-397-1340
Fax. 416-397-1354
www.torontobotanicalgarden.ca
Poison Ivy (Rhus radicans L.)
Poison ivy is a perennial shrub like plant, 20 cm to 2 m (2 to 7 ft) tall, containing poisonous oil called urushiol or toxicodentrol. Its leaves, on long stalks 10 to 35 cm (4 to 14 in) long, are divided into three broad, pointed leaflets (smooth or toothed). The many veined leaflets can vary greatly in size, but are usually oval in shape with pointed tips, up 4 inches long. When mature the leaves are commonly dark, glossy green above and slightly hairy below. They are reddish in spring when they emerge and become various shades of yellow, orange or red in autumn. Gray berrylike drupes follow small, yellowish or greenish flowers.
There is a climbing or trailing form that is found in southwestern Quebec.
Poison ivy is a member of the cashew family (Anacardiaceae). Poison ivy is often confused with other species (e.g. Poison oak) that does not grow in Ontario. It has highly variable growth forms, which makes classification confusing. Poison ivy is often referred by two names: Rhus radicans and Toxicodendron radicans. Some writers even refer to shrubby forms as poison oak, adding to the confusion.
| Poison oak: | The name poison oak is often applied to the shrub like forms of poison ivy and to at least two similar plants considered separate species of the cashew family - Rhus quercifolia, native to the southeastern U.S. and R. diversiloba, native to the U.S. Pacific coast (sometimes referred to as Toxicodendron diversilobum). Both contain poisonous substances identical or closely related to that in poison ivy. |
| Poison sumach: | Poison sumac is considered more virulent than poison ivy. Also of the cashew family, poison sumac (Rhus vernix, sometimes referred to as Toxicodendron vernix) inhabits the eastern United States. A shrub or small tree, it grows 6 m (20 ft) tall and has a smooth gray, black-speckled bark. Its leaves, with 7 to 13 smooth-margined leaflets, are 15 to 38 cm (6 to 15 in.) long, have bright red stalks and scarlet fall coloration. Small, greenish white or yellowish green flowers that grow in drooping clusters on purplish stalks are followed by clusters of small, grayish, berry-like drupes. |
Poison ivy is often found in large colonies. The plant spreads by means of running rootstocks that extend up to 12 ft from the parent plant. Birds spread the seeds. In spring the reddish leaves appear on old stems or on new ones that rise from stolons. After the leaves expand they take on their characteristic shiny, dark green colour. Poison ivy is found in many habitats from woodlands to fields and can grow unabated in poorly tended areas such a roadsides or paths. It grows well in rocky, dry, well-lit areas.
Allergy to poison ivy is one of the most common in North America. Contamination by poison ivy can occur through direct contact to any part of the plant, indirect contact (such as handling clothing, pets, garden tools contaminated with urushiol) or by exposure from smoke from burning plant parts. Sensitivity to an oily residue (urushiol) can occur at any time. Response will vary with the individual. The resulting dermatitis is limited first to the site of contact but may later spread (if the urushiol is spread). Response can range from itching and redness to severe swelling with oozing blisters.
The City of Toronto adopted a new municipal by-law (spring 2004) that restricts the use of pesticides. For details about the by-law visit the Pesticide by-law page on Toronto Public Health's Web site at www.city.toronto.on.ca/pesticides or www.toronto.ca/health. Questions may be e-mailed to pesticide@toronto.ca.
Immediately after contact with this plant, wash the affected area with copious amounts of cold water and soap to remove as much of the urushiol as possible (using hot water will open the pores enabling further absorption of the contaminant).
Contact your druggist or doctor for additional treatment options.
It appears that upwards of 90% of the population may be allergic to poison ivy. Exposure to only an extremely tiny amount of urushiol can cause a response. Frequency and length of exposure is important. The more a person is exposed the more likely he/she will respond. Urushiol stays active on surfaces (including dead leaves) up to five years. Stay away from forest fires or burnings that may cause the urushiol to become air borne. Poison ivy is considered a noxious weed in Ontario and should be removed by landowners.
Factsheets are produced by the Toronto Master Gardeners in association with the Toronto Botanical Garden. They provide introductory information about a broad range of horticultural topics and are intended for personal use and study purposes. Should your gardening group or organization wish to use multiple copies we ask that you inform the Toronto Botanical Garden at info@torontobotanicalgarden.ca.
Date revised: January 8, 2006
