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Dangerous Plants
by Dan Clost
by Dan Clost


First serious garden earned 25 cents from the Kemptville Horticultural Society when I was 12. Have been poor in horticulture ever since but rich in spirit.

Went to work writing the Good Earth column (over 500 articles published in newspaper, magazine, website and journal.) and learned that what was printed wasn't what I wanted to say and certainly not what Gentle Reader understood me to say. Subsequently have developed a certain clarity and economy of words.

Day job- nursery and production manager for a large nursery/garden centre
Side job- Garden restoration and renovations, design consultations, remedial pruning.
Night job- garden writer and communicator (overnight success in another 20 years)

Dan gardens in Canadian Zone 5b

June 5, 2011

My e-mails are full of questions about the Giant Hogweed. We are constantly getting calls at work concerning sightings of this "new" weed. Recent media reports have this plant growing everywhere, with huge numbers of people being scarred for life and even the possibility of blindness (both temporary and permanent) by the sap. I have noticed a sameness of arm and scar in the photos that accompany these stories.

Yes hogweed is around; in fact, it probably has been around for a very long time but, because the low incidence of contact and susceptibility by people, it is not very well known. There is a common hogweed, in fact there are I am not a Giant Hogweed expert. I’m not even a Little Hogweed expert. I could do what some of the "instant expert" media folk have done- prepared a synopsis of a quick internet search married up with a few downloaded pics and an instant expert is born. I’ve never seen a giant hogweed except in pictures. The flowers (umbrella like in shape) do look a lot like wild carrot, Daucus carotus or Queen Anne’s Lace. One huge difference between the two is you look down at the wild carrot and you look waaaay up at the Giant Hogweed. I also read that purple blotching on the stems I is indicative as are the presence of bristles. My suspicion though is that eight feet tall or more is the eye-catching feature.

Our local municipal folk haven’t seen it yet either but lots of Queen Anne’s Lace is being mistaken for it. Again, are you looking up or down? There has been one reported sighting in the Stockdale area by a reputable (read a knowledgeable plantsman) landscaper.

In fact, there was some at the Frankford Golf Course but it was removed long before the current furor. I did send e-mails to our closest municipalities, Quinte West and Belleville. At QW, I was directed to the Health and Safety Employee Services Officer who was quite helpful. The city had already contacted Jeff Cutten, a hogweed expert at the Ministry of Ontario Environment; as well they consult with Don Bourassa of the Ministry of Natural Resources. They had not seen any yet (the sighting at Stockdale not yet checked out) although they have seen a lot of Queenie. If you do think you have spotted it, then give those folks a call but expect them to ask you for a photo.

The man in the know for the City of Belleville is Chuck Naphan, who happens to be an old friend. (He’s ever so much older than I.) Chuck sent along a fax from Weeds of Ontario, Publication 505 in which common hogweed is included. Their, B’vlle, experience matches that of Trenton. So, although it may take a phone call or two to get to the person who knows, rest assured that our municipal employees are on the job.

Gentle Reader, I’m not bent out of shape over this one but please don’t think I’m discounting it. If I were known to be one of those susceptible to sap-induced problems, I might take a different stance. For example, most folks will get a mild rash when they contact poison ivy. Me? It covers me from head to toe, and I have spent some uncomfortable days in the hospital as a result. Poison ivy is number one on my weed hit list.

What else do you think might be found in the ditches? How about Poison Hemlock, same family as giant hogweed, been here forever, and could kill you if you eat it. How about wild oleander- did you know an ounce of oleander leaves can kill a thousand pound horse? I did the "become an instant expert" thing by taking am OMAFRA internet quiz.

Did you know that giant Hogweed was sold as a landscape plant? I found two sources still selling it for that purpose in the United States. How could anyone be that stupid, right? Think about the Castor bean plant (Ricinus communis, source of ricin poison), or Datura (hallucinogenic with toxic overdose possibilities)…in fact, the Landscape Ontario website lists 72 commonly sold plants that have toxic or deleterious effects to humans.

If you do have Giant Hogweed, take comfort knowing that it is an annual. When you see the flowers, have someone take a photo of you standing under them. Then cut them off before they turn to seed, slip them into a plastic bag and let them rot. Wear gloves.

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