Poison Hemlock

Invasive:

Queen Ann’s Lace, or Wild Carrot (Daucus carota) is sometimes mistaken for Poison Hemlock, but this plant has one densely-packed, umbrella-shaped flower cluster on a narrow, hairy stem. Wild Carrot also flowers later in the summer.

 

 

 

 

Native:

Water Hemlock (Cicuta maculata) is also similar to Poison Hemlock, but the leaf veins end in notches between the teeth of the leaflets, whereas in Poison Hemlock they end at the tips of the teeth.

Poison Hemlock originates from Europe, and was introduced in North America as a garden ornamental.

Poison Hemlock thrives in wet ditches and moist disturbed sites, but it can also withstand dry soils. It is often found near roadsides, field borders, hiking trails, railroad tracks, stream banks, irrigation ditches, waste areas, riparian woodlands and open floodplains.

This plant spreads by seed. Poison Hemlock is a biennial plant; it forms a short, leafy rosette the first year, and develops a tall hollow stem and several clusters of flowers the following season. One plant can produce over 1000 seeds, which remain viable in the soil for 3 – 5 years, leading to the rapid formation of a seed bank.

Poison Hemlock seeds are spread by machinery, on clothing, or in transported soil. They are also dispersed to a lesser extent by water and wind.

Poison Hemlock is not yet found in the Sea to Sky Corridor, so the best approach to controlling its spread is by PREVENTION.

Learn to identify Poison Hemlock: use the images presented in this profile page to learn how to identify Poison Hemlock.

What to do if you spot it: You can report any Poison Hemlock sighting by clicking here.

 

DO:

• Regularly monitor properties for weed infestations.
• Ensure soil, gravel, and fill material are uncontaminated before transport.
• Minimize soil disturbances (e.g. use grazing plans that prevent soil exposure from overgrazing), and use seed mixes with dense, early colonization to revegetate exposed soil and resist invasion.
• Maintain a strong population of native perennials to provide competition to any Poison Hemlock plants.
• Ensure all plant parts are bagged or covered to prevent spread during transport to designated disposal sites (e.g., landfill).

DO NOT:

• Do not unload, park or store equipment or vehicles in infested areas; remove plant material from any equipment, vehicles or clothing used in such areas and wash equipment and vehicles at designated cleaning sites before leaving infested areas.
• Do not plant Poison Hemlock in a garden, no matter how well-contained its enclosure may seem.
• Do NOT compost! Instead, dispose of Poison Hemlock in the general/household waste stream at the landfill as the seeds will be able to persist the composting process.
• Do not move soil, gravel, or fill material that has been contaminated with Poison Hemlock.

 

Control

Mechanical

• Please exercise extreme caution when working near Poison Hemlock. Minimize exposure by wearing gloves and taking frequent breaks when pulling or mowing large amounts of plants.
• Mowing or hand-pulling before seed set will eventually deplete the seed bank.

Chemical

• Since Poison Hemlock tends to grow in wet areas, the use of herbicides may be restricted or impossible.
• Where possible, foliar applications at the rosette stage (before the plant flowers) of dicamba, 2,4-D, and glyphosate have been used for chemical control of Poison Hemlock.
• Herbicide treatment may need to be repeated for several years until the seed bank is depleted.
• We recommend that any herbicide application is carried out by a person holding a valid BC Pesticide Applicator Certificate. Before selecting and applying herbicides, you must review and follow herbicide labels and application rates; municipal, regional, provincial and federal laws and regulations; species-specific treatment recommendations, and site-specific goals and objectives.

Biological

No biocontrol agents are available in BC, but Agonopterix alstroemeriana (moth) was accidentally introduced into the US and feeds exclusively on Poison Hemlock. It is used as a biological control agent in Idaho, Oregon and Washington, but it is not found in BC.