Stem

  • Up to 10 ft. tall, green with purple spots, stout, hollow except at nodes and highly branched with lengthwise ridges
Photo of poison-hemlock stem
 

Leaves

  • Triangular, 4-12 in. long, finely pinnate-divided (fern-like) and lack hair (glabrous); leaflets have toothed edges; foliage has a musty odor
Photo of poison-hemlock rosette
 

Flower

  • Small and white; arranged in umbrella-like clusters at end of a stalk
Photo of poison-hemlock with white flowers
 

Root

  • Thick, deep taproot
Photo of poison-hemlock small bush

Other

  • Grows best in moist sites; often infests crop fields, waterways, roadsides and waste areas; known to occur in Carson City, Douglas, Elko, Lander, Lincoln, Lyon, Nye, Storey, Washoe, and White Pine counties
  • Biennial; reproduces by seed
  • Highly toxic to animals and humans when consumed 
 
Photo of poison-hemlock with white flowers

Control

  • Repeated mowing or tillage prior to seed production is effective; hand-removal by cutting the taproot below the crown can also eliminate plants, avoid contact with skin
  • An insect biological control agent is available 
  • Apply 2,4-D, chlorsulfuron, glyphosate, metsulfuron or triclopyr to actively growing young plants; aminopyralid, imazapic, or imazapyr preemergence or on young plants
Blecker, L., Creech, E., Dick, J., Gephart, S., Hefner, M., Kratsch, H., Moe, A., Schultz, B. 2020, Nevada Noxious Weed Field Guide – Poison-hemlock, Extension, University of Nevada, Reno, Field Guide

Learn more about the author(s)

Heidi Kratsch
Heidi Kratsch
 

Also of Interest:

 
Managing Poison and Western Water Hemlocks
This fact sheet contains several ways to manage poison and western water hemlocks by taking a look at the habitat, impact, identification, and weed management options.
 Graham, J. and Johnson, W. 2004, Extension | University of Nevada, Reno, FS-04-09
 

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