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Poison Hemlock

Conium maculatum



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, - See more at:



Invasive Plant Atlas of the United States

Texas Invasives

Center for Aquatic and Invasive Plants


Early Detection & Distribution Mapping System

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