Hazardous plants

Some plants that grow in Rouge National Urban Park can be hazardous. Learn how to identify and avoid them.

Poison ivy

Poison ivy can often be found growing along the edges of park trails. Touching the plant transfers an oily resin called urushiol to your skin, which causes an itchy rash or blisters. Poison ivy can be identified by its clusters of three leaves, with the middle leaf having a longer stem than the two side leaves. Poison ivy can grow in short patches close to the ground or as a vine that climbs up trees, shrubs, and posts. The plant appears reddish in the spring, green in the summer, and red, orange, or yellow in the fall. You can avoid contact with poison ivy by staying on trail and keeping your dog on a leash to reduce the chance of the resin transferring from your pet's fur to your skin.

Stinging nettle

Stinging nettles are covered in tiny hollow hairs called trichomes. These trichomes detach from the plant when you brush against it and act as tiny needles that inject chemicals into your skin, causing a painful stinging sensation. Stinging nettle grows to about 1 metre in height and has jagged egg or heart shaped leaves that grow in pairs on opposite sides of the stem. Stay on park trails to avoid accidental contact.

Cow parsnip

The sap of this plant contains a phototoxin which reacts with UV radiation. It can cause a rash if it gets onto your skin when you are out in the sun. Cow parsnip grows to 1 to 3 metres in height and has clusters of small white flowers, thick stems, and large compound leaves.

Spotted water hemlock

Spotted water hemlock is considered the most poisonous native plant in Ontario. All plant parts contain a potent toxin called cicutoxin. Ingesting the plant can cause severe illness or death in humans and animals.

Spotted water hemlock is present throughout North America and can usually be found growing near water. The plant has tiny white clusters of umbrella-shaped flowers that bloom between June and August and reaches an average height of between one and two metres. If you find spotted water hemlock in Rouge National Urban Park, please email rouge@pc.gc.ca or call 416-264-2020 and be prepared to share the plant's location and GPS details.