Poison hemlock is now in full growth around Idaho, noxious weed officials are warning, and people are being asked to watch for it and remove it wherever possible; hand pulling, while wearing rubber gloves, is recommended, along with herbicide treatments. “This dangerous noxious weed presents an issue of public and animal safety,” said Roger Batt, coordinator of the Idaho Weed Awareness Campaign. “It is so toxic that horses and cows literally can die within hours after eating this poisonous plant.”
Poison hemlock grows three to eight feet tall with a smooth green stem that’s usually spotted or streaked with red or purple spots. It has finely divided, lacy leaves that look like those of a carrot plant, and small, white clustered flowers. It also has a taproot that’s white and fleshy; there’s more info here. Batt said there are documented cases in which people have mistaken poison hemlock’s roots for parsnips and its leaves for parsley or fennel.