Giant Hogweed is a member of the parsley or carrot family. It is characterized by its size and may grow to 5 to 7 metres in height. It has a stout dark reddish-purple stem and spotted leaf stalks. The stem and stalks are hollow and the stems may be 5 to 10 cm in diameter. The compound leaves of giant hogweed may reach over one metre. Each leaflet is deeply incised. The flower cluster is a broad flat-topped umbel composed of many small white florets.
DO NOT TOUCH THIS PLANT - The plant exudes a clear watery sap, which sensitizes the skin to ultraviolet radiation. This can result in severe burns to the affected areas resulting in severe blistering and painful dermatitis. These blisters can develop into purplish or blackened scars. The sap can cause blindness if it enters the eyes.
Giant hogweed may grow along streams in Ontario where it forms a dense canopy out-competing native riverbank species and results in an increase in soil erosion along the stream banks where it occurs. While giant hogweed often grows in wet areas, it may also colonize in a wide variety of habitats such as along roadsides, other rights-of-way, vacant lots, streams and rivers.
Think you've spotted giant hogweed? Here's how to tell.
Ministry of Agriculture and Food Giant hogweed
Giant Hogweed - Ontario Invading Species
Poison-ivy may grow as dwarf, shrubby plants only a few centimetres high and carpeting the ground, as upright plants 60-90 cm high, or the vine-like form may twine around trees, shrubs and posts, and reach a considerable distance above the ground. Each leaf of poison-ivy consists of three leaflets so the leaf is said to be "compound", with the stalk of the middle leaflet longer than the stalks of the two side leaflets. All three leaflet stalks are joined together at the tip of one much longer stalk, called the petiole. When there are several leaves they usually alternate from one side of the stem to the other.
In the spring and early summer, the unfolding leaflets are reddish or bronzy green and they droop from the ends of the petioles. The leaflets gradually become firmer and stand out nearly level with the end of the petiole, and by the summer, their color has changed to bright green.
Poison ivy may cause contact dermatitis which can range from a mild, short-lived redness to severe swelling and blisters. Often, the rash contains linear streaks of tiny, itching blisters. The rash area may be very small or may cover a large area of the body.
Poison ivy occurs under forests, in edges of woodland, meadows, waste areas, fence lines, and roadsides throughout most of southern Ontario.
Ministry of Agriculture and Food - Poison Ivy
Government of Canada - Poison Ivy
Ontario Trees and Shrubs by Walter Muma - Poison Ivy