Impressive but invasive

text and photos : Norma A. Hubbard (August 2013)

Before we moved in, the previous owners had walked the land with us to point out trees and plants. I can clearly recall how excited she was to tell me about an impressive plant that grew to great heights. She said a friend had given it to her. The first spring it didn’t grow tall but was spreading everywhere, so I cut it back. This summer was a different situation. It grew rapidly and was spreading again, but it was also growing tall stalks. Again, I cut it back but left some stalks. I did not know it was Giant Hogweed (Heracleum mantegazzianum) and I was waiting for it to flower. Then we saw a warning on the news, but not soon enough. Unfortunately, Ron had been working around these plants and he must have had some contact with the sap. Since we did not know it was dangerous, he had not taken any precautions. I was just lucky that I was not exposed to the sap since I usually wear gloves while gardening.

Contact with the sap causes a reaction on the skin similar to burns. The sap reacts to UV rays, which causes the skin to become sensitive and even blister after exposed to sunlight. Severe cases need medical treatment. Initial contact is not painful or itchy, and symptoms can develop within 48 hours after exposure. According to Health Quebec, if you do come in to contact with the sap you should, “remove the sap as quickly as possible without spreading it. Use a sheet of absorbent paper and do not rub. Wash the affected area with soap and rinse thoroughly with water. Then wash your hands. Change and wash your clothes to avoid contaminating other parts of your body or other people. Cover affected areas (gloves, long pants, and long sleeves) to avoid exposing them to light (including artificial light) for at least 48 hours.” Sensitivity to the sun can remain up to several months. Anyone exposed to the sap should contact a doctor.

This plant should never be planted nor be encouraged to grow in our area. Not only is it a health risk to us, it is also an environmental concern. As a non-native but inva- sive plant, it can quickly take over space inhabited by native plants. Giant Hogweed is biannual-perennial plant that grows between 2 to 5 meters high. It has white flowers and the stalk is hairy with burgundy-coloured spots. It first ap- peared in Quebec in 1990 and is found in several regions.

If you find Giant Hogweed on your property, before attemp ing to remove it you must protect yourself. Health Quebec suggests you should not expose any skin by wearing pants, long-sleeve shirt, gloves, boots, hat, and glasses (a full-face visor would be ideal, but glasses are a minimum). If possible, wear synthetic or non-absorbing type clothing. If you are using a mechanical weed-cutter or mower, make sure no one else can be hit with sap or plant cuttings. Clean all tools well, then carefully remove work clothing to avoid contact with skin. Wash clothing immediately and be sure to wash your hands and face with plenty of soap and water. I try not to use herbicides, but if you do, be sure to follow instructions carefully. One natural herbicide is water, vinegar, and dish soap – but I haven’t tried it. Whichever method you use, do so with plenty of caution.

Reference: www.msss.gouv.qc.ca