Outdoor Safety: Hazardous Plants Information

Across Ontario there are many different hazardous plants that can leave you with an unpleasant outdoor experience.  The best way to avoid such an experience, is to know what plants to watch for and how to handle these plants if they are present.

Poison Ivy and Sumac
Contact with poison ivy and poison sumac can result in painful rashes caused by an oil in the plant. The oil can be transferred to the skin either directly or through cross-contamination with equipment and/or clothing and can be contracted from the plant any time of the year.

Poison IvyPoison Ivy
Poison ivy can be found as a low lying herbaceous plant or as a climbing vine. The leaves hang from the stem in groups of three. The lobes on the bottom edge of the lower leaves are more distinct than the top edges (1), the middle stem is longer than the other two (2), and the middle leaf is only lobed on the top half of the leaf (3) see below.

 Poison SumacPoison Sumac
Poison Sumac takes form as a small shrub to tree ranging anywhere between 1.5 to 6 metres in height. The plant has red stems containing 7 to 13 leaflets. Each leaflet is between 5 and 8 centimetres long and between 2.5 and 5 centimetres wide. The leaflets appear bright orange but change to dark green and glossy mid-season finishing off with a bright red/orange colouration. Poison sumac has bright white berries when ripe and a smooth edge.  The sap of these plants contain chemicals that react with skin and cause photodermatitis, a condition where the skin becomes more sensitive to UV rays. The reaction can result in severe burns and blisters that result in long term scarring.

Wild ParsnipWild Parsnip
The leaves of Wild Parsnip are heavily toothed and can have a distinct mitten shape. The plant has 5 to 7 leaflets per leaf that form a diamond shape leaflet structure. The plant produces clusters of individual bright yellow flowers, 1-20 cm in diameter. Wild parsnip can grow to a height of 1-1.5 metres.


Giant Hogweed Giant Hogweed 2Giant Hogweed
Giant Hogweed can grow to be up to 5 meters once fully grown. The plant lives its first year as just a rosette of leaves and matures to develop a tall stalk. The leaves can be a meter wide with jagged deeply cut leaflets. The stem is hollow, similar to bamboo, and is covered in red blotches and bristles. Once the Giant Hogweed starts to flower it creates a large white umbrella of flowers. The flower cluster can be up to 120 cm wide containing close to 40 branches with 30 – 40 white flowers, each.

Stinging NettleStinging Nettle
Stinging Nettle is covered in sharp hollow hairs that can inject irritating chemicals into the skin if contact occurs. Reaction to the chemical can result in an itchy and burning sensation that may last for more than 12 hours. Stinging nettle can grow up to 1 metre in height. The leaves have serrated edges and are usually 10 to 15 centimetres in length. Each layer of leaves is perpendicular to the layer above and below it.

Working With Hazardous Plants

  1. Wear long pants and long sleeve clothing when working outside to protect yourself
  2. Wash or dispose of all equipment that may have come into contact with plants
  3. Do not burn or use power tools near Hazardous Plants
  4. Do not wash skin in warm or hot water
  5. Do not attempt to remove any hazardous plants. Plants should be removed by trained personnel.

Sources of Information:

The County of Hastings would like to recognize the County of Peterborough for the generous sharing of their information.

If you spot any of the plants mentioned in this brochure, please notify the County Weed Inspector at: 613-848-1010 or weedinspector@hastingscounty.com