Poison Ivy

While poison ivy (Toxicodendron rydbergii) is a native plant, it can have invasive tendencies. Poison ivy is also known as western poison ivy to distinguish it from eastern poison ivy (T. radicans), and often incorrectly referred to as poison oak. Western poison ivy, hereafter referred to simply as ‘poison ivy’, is the most northerly occurring taxa within the Toxicodendron complex, ranging across southern Canada from British Columbia to Nova Scotia. In BC, poison ivy occurs east of the Cascade Mountains and is scattered and locally abundant mostly in the dry Okanagan Basin, but also in widely scattered locations north to Williams Lake. Poison ivy commonly grows in open Douglas-fir and ponderosa pine forests, frequently in moist gullies, along lakeshores or at the base of talus slopes. Poison ivy is considered a ubiquitous weed throughout much of its distribution and easily invades disturbed areas such as roadsides, floodplains, fence lines, cutblocks and railroad rights-of-way.  Throughout the western portion of its distribution, poison ivy is usually associated with riparian (river, creek or lakeside) communities, with plants frequently found on floodplains and river terraces. Popular walking and biking trails, such as along the Okanagan River channel near Oliver, is where people typically come into contact with this plant.

Poison ivy is a spreading, deciduous shrub, typically reaching heights of less than 1.0 metre tall, although plants can reach heights of up to 3 metres which I have personally observed along the old railway bed near Oliver. Stems are somewhat woody, arising from a heavily branched rootstock.  Long-stalked leaves are borne alternately near the summit of the stem and are divided into three coarse-toothed leaflets, hence the saying “leaves in three, let them be”. The shiny green leaves turn to bright scarlet in the fall. Ivory-coloured fruits are usually well developed by fall and often persist on the plant through the winter.

Keep your distance from this plant. Approximately 90 percent of North Americans are allergic to poison ivy. It has a milky oil called urushiol (pronounced oo-roo-shee-ohl) which can cause redness, swelling and blistering of human skin within a few hours of contact.  For the first time sufferer, it generally takes longer for the rash to show up – generally in 7 to 10 days. Plants must somehow be damaged in order for the oil to be emitted.  Skin rashes can result from contact with either the liquid oil or its dried, blackened residue. Secondary objects such as boots, pants, hand tools or the fur of pets can also transmit the poison. Since the skin reaction is an allergic one, people may develop progressively stronger reactions after repeated exposures, or show no immune response on their first exposure, but show sensitivity on following exposures. As urushiol oil stays active on any surface, including dead plants, for up to 5 years, anyone that comes into physical contact with poison ivy must take extreme caution.

Most importantly, learn to identify poison ivy plants in all stages and be fully aware of the precautions that should be taken to prevent exposure. Teach your kids and grand children about the “leaves in three” and explain the importance of not touching the plant. If exposed to poison ivy, cleanse exposed skin with generous amounts of isopropyl (rubbing) alcohol.  Wash exposed skin with water, then take a shower with soap and warm water. Do not use soap before this point because soap tends to pick up some of the urushiol from the surface of the skin and move it around. Clothes, shoes, tools, and anything else that may have been in contact with the urushiol should be wiped off with alcohol and water.

If you have poison ivy on your property and desire removal, CLICK HERE for further information or contact your local Invasive Plant Coordinator for advice. Its removal requires considerable caution and because of the creeping roots, it can prove challenging.

Despite the negative associations most people have with poison ivy, it does possess some redeeming qualities. Poison ivy helps protect the soil and adds beauty in the summer with its dark green leaves and in autumn with bright colors to forests and shrub lands. Although it causes browsing animals no ill effects, western poison ivy is low in protein and energy and consequently is only occasionally grazed by domestic animals and wild ungulates. However, quail, wild turkeys, and some songbirds eat the fruits. It does provide cover for small mammals and birds. In herbal medicine, extracts of the leaves of this and other Toxicodendron species have been and still are used to treat the herpes virus, palsy and rheumatism.

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