How to Get Rid of Poison Hemlock Safely

Poison hemlock is a safety problem before it is a removal problem. All parts of the plant are toxic if swallowed, and the sap can irritate skin. Do not pull it bare-handed, do not burn it, and do not let children or pets near a pulled pile.

Read the safety rules first. Then decide on a method.

Before you start: the safety rules

These come from Penn State Extension and the University of Maryland Extension.

• Every part of the plant is poisonous. Penn State Extension says all parts are toxic to humans and other animals, and that the roots and seeds contain the highest concentration of alkaloids. The University of Maryland Extension says the plant can be fatal to livestock and humans if eaten.
• The sap can hurt your skin. Penn State Extension describes the sap as a skin irritant. The University of Maryland Extension notes that some people and animals develop dermatitis from direct contact.
• Do not burn it. The University of Maryland Extension warns against burning poison hemlock because of accidental inhalation by people or nearby animals.
• Cover your skin. Wear gloves. Cover your arms and legs so sap cannot reach bare skin. Do not touch your face while you work.
• Keep it away from your mouth. Do not eat, drink or smoke while handling it, and wash your hands and tools when you finish.
• If someone swallows any part of the plant, get emergency medical help right away. Do not wait for symptoms.

Penn State Extension adds a warning about power tools: even a weed trimmer needs precautions so that plant material does not come into contact with your body. That is a good reason to leave trimming to the last resort, not the first.

Identify it before you touch it

Poison hemlock is a biennial. In its first year it forms a low rosette of fern-like leaves. In its second year it sends up a stem, branches and white umbrella-shaped flowers, then dies after setting seed.

The stem is the safest feature to check from a distance. It is smooth, hollow and marked with purple spots. The University of Maryland Extension describes the plant as six to ten feet tall; Penn State Extension gives six feet. Height varies with site, so use the stem and the flower shape, not the height alone.

The dangerous confusion is with Queen Anne’s lace and other carrot-family plants. Check the stem for purple spots before you touch anything. If you are not certain, do not touch it. See poison hemlock vs Queen Anne’s lace and the poison hemlock species profile.

Pull, cut or treat

The right method depends on how many plants you have and where they are.

The logic behind the table is simple: kill the plant before it makes seed. The University of Maryland Extension calls prevention of seed production the best defense. Seeds drop close to the parent plant and can move with water, birds and rodents, and they stay viable for two to three years.

When to treat poison hemlock

Treat rosettes. That is the one timing rule that both extension programs support.

• First-year rosettes are the target. They are low, they are easy to spot in early spring, and they have not yet spent energy on a flower stalk.
• Second-year plants are harder to kill and are about to make seed. Treat them before the flowers open, or stop and get advice if you cannot.
• Flowering runs from June into August in Pennsylvania, according to Penn State Extension. The University of Maryland Extension gives June and July for Maryland. Seed is set after that.

The University of Maryland Extension says control may take more than one or two years, and that a single application will not solve it. Plan for a follow-up season.

What the extension programs name for herbicide

Penn State Extension names diquat, pelargonic acid, glyphosate and 2,4-D as post-emergent options. It notes that the first three are non-selective, meaning they injure or kill most green plants they contact, and that there are no pre-emergent herbicides for poison hemlock in ornamental settings. The University of Maryland Extension names glyphosate and 2,4-D.

This page does not give rates or mixes. Product strengths differ, and the label for the product you are holding is the only rate that applies. Follow the product label; the label is the law. If the label and this page disagree, the label wins.

Two practical points from the sources:

• Treat early, when the plant is a rosette. The University of Maryland Extension says most products require action at the rosette stage.
• If the plants are near water, stop and ask before you spray. Label restrictions for aquatic sites are different, and Penn State Extension notes that poison hemlock sometimes grows along the banks of water bodies.

What to do with the material

Bag it and put it in the trash. Do not compost it, and do not burn it.

• Pulled plants should go straight into a bag, not into a pile where children or animals can reach them.
• Cut flower heads should be bagged separately so seed cannot scatter.
• Gloves and tools should be washed after use.

The invasive plant disposal guide covers bagging, solarizing and state rules in more detail.

When to stop and call for help

Stop and get advice if any of these are true:

• The stand is too large to clear before the plants flower.
• The plants are within reach of a stream, ditch, pond or well.
• The plants are in a pasture or anywhere livestock graze.
• The plants cross a property line.
• You are not sure the plant is poison hemlock.

Call your county extension office or your state agriculture department. For a stand near water or livestock, ask before you buy or apply anything, because the label restrictions are different and the wrong product can create a second problem.

If anyone may have eaten any part of the plant, call Poison Control at 1-800-222-1222 (free, confidential, 24 hours) or use poison.org right away. If the person is having trouble breathing, a seizure or is unconscious, call 911.

Related WildScope pages

• Poison hemlock species profile for identification.
• Poison hemlock vs Queen Anne’s lace for the look-alike that causes the most confusion.
• How to dispose of invasive plants for bagging and trashing the material.
• When to treat invasive plants for seasonal timing.
• Removal guides for other species.