HISTORY: Originally from Europe, poison hemlock is an aggressive invasive weed commonly found along roadsides and ditches and poorly drained areas.
FEATURES: The plants grow up to 10 feet high and have smooth, hairless green stems covered in purple blotches. Poison hemlock has finely divided fern-like leaves, flat-topped clusters of tiny, white five-petaled flowers and a musky, unpleasant odor described as similar to mouse urine.
POISONOUS: The plant contains poisonous compounds affecting the nervous system. Initial symptoms may include a burning sensation in the mouth, nausea, vomiting, confusion, trouble breathing and muscle paralysis. When death occurs, it is usually rapid and due to respiratory paralysis. There is no antidote to the poison.
REMOVAL: Wear gloves to protect skin from plant juices. Small patches may be dug up - including roots - but mowing poison hemlock won't kill it. Put the plant in a sealed garbage bag, let it bake in the sun and then throw the bag in the trash. Do not compost - the dried plants remain toxic. Treat clothing similar to poison oak and wash it separately. If you get juice on your skin, wash immediately. Herbicides containing glyphosate are effective in killing poison hemlock. The best time to spray is when the leaves are just a basil rosette and before the plant forms flowers. The plants may regerminate and require follow-up control.
MORE: For help identifying noxious weeds, call the Cowlitz County Noxious Weed Control Board at 360-577-3117 or go to www.co.cowlitz.wa.us/noxiousweeds. For more about poison hemlock poisoning and symptoms, call the Washington Poison Center at 1-800-222-1222.
Source: Washington State Noxious Weed Control Board