Monday, July 12, 2010

Giant Hogweed in Ontario

The CBC reported on Thursday that the invasive and toxic giant hogweed (Heracleum mantegazzianum) has been spotted in Eastern Ontario. Contact with the plant's sap can cause severe burns and even blindness if the sap gets into the eyes. As a nature photographer who frequently goes around stalking crickets and damselflies in all sorts of weeds, I was keen to learn how to stay away from this one.

From the pictures in the CBC's report, the plant looked alarmingly like Queen Anne's lace to me, so I thought I'd do some research and learn how to identify it.

Wikipedia has a much better picture in its article on giant hogweed, which thankfully eliminates any possibility of confusing it with Queen Anne's lace. The plant can reach 2 to 5 meters, and occasionally up to 7 meters. From the Wikipedia article:

"It is further distinguished by a stout, dark reddish-purple stem and spotted leaf stalks that are hollow and produce sturdy bristles. Stems vary from 3–8 cm in diameter, occasionally up to 10 cm. The stem shows a purplish-red pigmentation with raised nodules. Each purple spot on the stem surrounds a hair, and there are large, coarse white hairs at the base of the leaf stalk. The plant has deeply incised compound leaves which grow up to 1-1.7 m in width."

The Ontario Federation of Anglers and Hunters has an identification page on its web site. In case of exposure, the OFAH recommends washing the exposed area immediately with soap and water, keeping affected areas out of direct sunlight, and seeking medical attention.


For comparison, this is my own picture of Queen Anne's Lace (Daucus carota) at the Rockcliffe Airport. It would be difficult to confuse these gangly stems with giant hogweed, but they do closely resemble those of water hemlock (Cicuta), which is highly toxic. Because I am not an expert by any stretch of the imagination, I find it safer to avoid touching any plants in the field, and to be careful where I step when I'm wearing shorts.

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