Description: This biennial herb can grow up to 8 feet tall. Poison hemlock has green stems with purple spots, is freely branched, and all parts are deadly poisonous. This plant has a five part white flower with mostly terminal umbels. It blooms June-August.
Ecological Threat: All parts of this plant are poisonous with the highest concentration in the seed. The alkaloid toxin affects both humans and livestock.
Biology & Spread: Poison hemlock often acts as a pioneer species that can quickly colonize disturbed sites. This trait means that it can displace natives during the early successional stages of a landscape.
Threat in Oklahoma: Poison hemlock can be mistaken for wild carrots or parsnips, poisoning the unsuspecting consumer.
Image Credit: Chris Evans, Illinois Wildlife Action Plan, Bugwood.org - See more at: http://www.invasive.org/browse/detail.cfm?imgnum=2117087#sthash.urJUGWEm.dpuf
Invasive Plant Atlas of the United States
Center for Aquatic and Invasive Plants