A Very Dangerous Weed....Giant Hogweed

 I was very surprised last year, as I am sure most people were, when I heard about the very dangerous weed growing in Ontario, the Giant Hogweed. Obviously this weed has been around for ages, just never heard of it before. So of course now when I am in rural parts of our town I keep a look out for it, and as it happens I do see it quite often.

This weed has dangerous sap which when exposed to sunlight can create a chemical reaction on your skin causing serious burns and scarring. This weed has also been known to cause temporary blindness and in some cases even permanent loss of sight. Because of how dangerous this weed is I warn new residents to our town about it. I think I can best describe it as looking like giant Queens Anne's Lace, which is a perfectly harmless and pretty weed. Below are some pictures of the Giant Hogweed.

From www.halton.ca 

What is giant hogweed?

Giant hogweed is an invasive plant known for its enormous size.The plant has hollow stems with dark reddish-purple splotches and coarse white hair. It can grow from 8 – 14 feet high (2.5 – 4 metres). The leaves of the plant can grow to 3 feet (1 metre) in width and have hairs on the underside.The plant produces flattened oval shaped fruit and in the summer, small white flowers form.

 Is the Giant Hogweed a Risk to Human Health? 

Yes. A clear watery sap is found in the stem and hairs of giant hogweed. Contact with sap can cause a skin reaction where skin becomes sensitive to the ultraviolet light in sunlight.Reactions can occur up to 48 hours after contact, and sensitivity can lead to painful blisters and burns. Blisters can lead to purple and black scars that may last for long periods. Skin reactions will depend on the sensitivity of the individual. Heat and moisture (sweat) can enhance the skin reaction. Contact with eyes can also cause temporary and sometimes permanent blindness.

 What if I accidentally come into contact with giant hogweed?

 * If any sap reaches your skin, you must wash it immediately with cool, soapy running water.

* Avoid exposure to the sun for at least 48 hours after contact. This is important since the sap increases photosensitivity of the skin.

* Contact a medical professional as soon as possible for additional advice and treatment.



What do I do if I find giant hogweed in a park or other public area?

 If you see giant hogweed on Town or City property, pleasecall your local area municipality.

 City of Burlington: 905-335-7600

Town of Halton Hills: 905-873-2601

Town of Milton: 905-878-7252

Town of Oakville: 905-845-6601


Where can I get more information?

 For more information on giant hogweed, visit:

 􀂆 Conservation Halton: www.conservationhalton.on.ca 

􀂆 Ministry of Agriculture, Food, & Rural Affairs: www.omafra.gov.on.ca 

􀂆 Ontario Weeds: Ontario’s Online Weed Information &Identification Resource: www.ontarioweeds.com 

􀂆 Ontario Federation of Anglers and Hunters: Invading Species Awareness Program: www.invadingspecies.com/ 

􀂆 Service Ontario e-Laws: Ontario Weed Control Act:




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