The Dangers of Giant Hogweed

Giant Hogweed is an invasive plant found throughout Ontario, including along the banks of the Grand River. When in bloom, it can grow to an impressive height of up to 14 feet. Key identifying features include large umbrella-shaped white flower clusters, thick green stems with distinctive purple blotches, coarse white hairs along the stems, and large jagged leaves that can exceed one metre in width.

While striking in appearance, Giant Hogweed poses a significant health risk. Its sap contains toxic compounds that can cause severe skin irritation, including burns, blistering, skin discolouration, and long-term sensitivity to sunlight. Symptoms may not appear immediately and can develop several hours after exposure.

If you come into contact with Giant Hogweed, avoid further sun exposure for at least 48 hours, as sunlight can intensify the reaction. Wash the affected area thoroughly with soap and cold water as soon as possible, ideally within 20 minutes of exposure. Avoid touching your face or eyes, and seek immediate medical attention if sap comes into contact with your eyes.

To help ensure a safe and enjoyable experience on the Grand River, we recommend wearing closed-toe footwear during portages, along with long pants and socks when travelling through natural shoreline areas. Visitors should remain on designated launch sites and trails and avoid entering dense shoreline vegetation whenever possible.