It's not pot. It's this:

Biologists and health officials in southern Ontario are scrambling to contain an invasive plant that can cause blindness and severe burns. Heracleum mantegazzianum, or giant hogweed, is a poisonous plant most recently found growing in Renfrew County, west of Ottawa. "The concern is it's a very poisonous plant, in the sense that if you get any of the sap from this plant on your skin, it can cause severe blistering and very bad burns," said Jeff Muzzi, manager of forestry services for Renfrew County.

"If you should happen to get the sap in your eyes, it can blind you either temporarily or permanently."

He said the burns can cause permanent scarring and any areas affected will be sensitive to sunlight for many years.