piggish hogweed

In late May, we were travelling through Quebec and at a picturesque roadside I saw something I had only ever heard about.  Giant Hogweed was brought to North America by avid gardeners who admired the huge, toothed, tropical-looking leaves and white umbrels of flowers that look like Queen Anne's Lace on steroids. 
But this is the stuff of nightmares.  The leaves and stems contain a sap that can burn the skin and even cause blindness if it get in the eyes.  The sap can't be washed off, and the effects can last for years.  The skin becomes super sensitive, and will burn over and over again when exposed to light.  What's more, this plant likes to colonize stream beds, and it produces thousands of seeds, which drop into the water and float on the current to colonize new areas further downstream.  Removing the stuff requires extreme care and a haz mat suit, so beware!

Purple spines along the stem are a sure way to identify this hazardous invasive.