Poison Plants
Credit: D. Gordon E. Robertson

 There are often hidden dangers in the great outdoors, and this includes a few of our native plants — some of which are poisonous to the touch.

The good news is that there are also a few homegrown antidotes, often right nearby. Keep reading to find out more, and click the links for images and more info:

The Big Three

The three most well-known contact poisonous plants are:

Symptoms

Symptoms can range from mild itchiness and redness, to skin blistering and hive-like swellings, to severe lesions with fever, depending on the individual.

Distribution

  • Poison ivy is found throughout southern Canada.
  • Poison oak is found mostly in southwestern BC.
  • Poison sumac is found mostly in southern Ontario and Quebec.

Antidote

Jewel weed, Impatiens capensis, is often recommended as an effective antidote, but there is some research that questions its effectiveness. However, if one is suffering from the painful effects of these plants, any nearby potential remedy is welcome. Simply crush and rub jewel weed onto the affected area.

Hikers should carry some calamine lotion if heading into areas where these plants are found — it will soothe the itch. Washing with soap and water several times also helps. 

Stinging Nettle – Urtica dioica

The stinging nettle's Latin name comes from “uro,” which means to burn — and “burn the skin” is exactly what it does. When skin comes into contact with this plant, its stinging hairs break off and force a stream of formic acid/histamine compound into the flesh, much like tiny hypodermic needles.

Symptoms

A painful sting followed by a rash, itching, swelling and numbness, depending on the person.

Distribution

Found across Canada, particularly in areas that were formerly cultivated. The presence of nettles is usually a good sign that the soil is fertile.

Antidote

Try rubbing the crushed horsetail plant (Equisetum species) juices or the leaves of the dock plant (Rumex obtusifolius) to relieve the sting and itch. One or both of these plants are often found growing in the same areas as stinging nettles.

Canada Nettle — Laportea canadensis

The Canada nettle also has stinging hairs on its leaves and stems and, when brushed against, has a similar effect as stinging nettles. Again, horsetails and dock plant work in this instance; however, applying water may increase the sting. This weed is found in moist woods and near streams across much of the country.

Yellow Lady’s Slipper – Cypripedium calceolus var. pubescens

The yellow lady's slipper is a native perennial wildflower orchid is found across Canada. It has tiny hairs that can cause itching and rashes of varying severity on susceptible persons, resembling the dermatitis caused by poison ivy and its relatives. Calamine lotion is your go-to remedy here.

Three More to Watch For:

Other native plants that can cause dermatitis in susceptible people include the following:

Canada fleabane (Erigeron vulgare): native on dry sites across Canada.

False ragweed (Iva xanthifolia): found across southern Canada.

Wild Ginger (Asarum canadense): a native wildflower of the woods of eastern Canada.

 This article originally appeared in our Summer 2013 issue; written by Jesse Trail.

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