How to Identify and Remove Poison Hemlock

Poison hemlock, also known as Conium maculatum, is an invasive, poisonous plant that can be harmful to humans and livestock if ingested. Learning how to properly identify and remove poison hemlock is important for safety. Here is a comprehensive guide on identifying poison hemlock and techniques for effective removal.

Identifying Poison Hemlock

Poison hemlock is a biennial or short-lived perennial herb that can grow to be 2-10 feet tall. Here are some key characteristics to look for when identifying poison hemlock:


  • Hollow, smooth green stems with purple speckles and a waxy appearance. Stems are branched and can be mistaken for wild carrots or Queen Anne’s lace.
  • Fern-like, lacy leaves that are doubly or triply pinnately compound. Leaves emit an unpleasant odor when crushed.
  • Umbrella shaped clusters of small white flowers that bloom in late spring. Flowers produce green ridged seeds.
  • Taproot is thick, white and looks similar to parsnips or wild carrots when young.


  • Often found growing along roadsides, ditches, edges of cultivated fields, streams, disturbed areas.
  • Thrives in direct sunlight. Tolerates a variety of soils and moisture conditions.
  • Common across North America except for Florida and the Gulf Coast states. Also found in Europe.


  • All parts of the plant contain the toxic alkaloids coniine and gamma-coniceine which disrupts the central nervous system.
  • Toxic alkaloids are most concentrated in the flowers and seeds. Even small doses can be fatal if ingested.
  • Handling the plant can cause skin irritation in some individuals. Wear gloves when removing.


  • Poison hemlock resembles several edible members of the carrot family, including Queen Anne’s lace and wild carrots. Be 100% certain before consuming any wild plants.
  • Water hemlock has clusters of white flowers like poison hemlock but has different leaf structures and habitat.

Removing and Controlling Poison Hemlock

Once positively identified, poison hemlock needs to be carefully removed and controlled to prevent growth and toxicity. Here are some effective methods:

Manual Removal

  • Wear protective gloves, long sleeves and pants. Rinse gloves after.
  • Hand pull small infestations, ensuring the entire taproot is removed.
  • Dig deep around the taproot using a shovel, then lift out the entire plant.
  • Place plant parts in thick garbage bags, seal and dispose of in a landfill, not compost.


  • Mow or repeatedly cut plants as they emerge to prevent flowering and seed production.
  • Be sure to collect and dispose of clippings to prevent spread. Do not compost.
  • Repeat cutting throughout growing season to deplete root stores.


  • Systemic herbicides like glyphosate (Roundup) are effective when applied early in the season.
  • Follow all label instructions carefully for application method and timing.
  • Herbicides may not kill the taproot, so monitor and repeat treatment as needed.


  • Goats and sheep can graze on poison hemlock without ill effects. Do not graze other livestock like horses or cattle.
  • Supervise animals closely and do not overgraze an area. Rotate grazing sites.


  • Maintain healthy pastures and rangelands that outcompete poison hemlock.
  • Seed disturbed areas with desired vegetation to prevent invasion.
  • Clean equipment, animals, clothing after exposure to prevent spread.

With vigilance and persistence, poison hemlock can be safely identified and removed. Combining control methods often leads to the best long-term results. Being able to recognize this toxic plant can help protect people, pets and livestock.

Frequently Asked Questions About Poison Hemlock

How long do poison hemlock plants live?

Poison hemlock is generally a biennial plant, taking two years to complete its lifecycle. It produces foliage the first year, then flowers, sets seeds and dies the second year. However, some plants may continue growing for several years as short-lived perennials if left undisturbed.

What temperature kills poison hemlock?

Poison hemlock is hardy in most climates and can withstand cold winters. Prolonged freezing temperatures under 20°F may damage or kill some plants, but seeds in the soil would still germinate in spring. Mature taproots are quite cold tolerant once established.

Does pulling poison hemlock spread it?

Pulling or digging up poison hemlock can spread seeds if the plant has already flowered and gone to seed. It may also cause bits of the taproot to break off and resprout. Be sure to remove the entire plant including all root parts, seal in bags, and dispose of properly.

Is poison hemlock illegal?

Poison hemlock itself is not illegal, but may be considered a noxious weed in some areas. You should check with your local county noxious weed ordinances to see if poison hemlock is listed as a prohibited or controlled plant. Methods of removal and control may be specified.

What animals eat poison hemlock?

Poison hemlock is toxic to humans and most livestock animals like horses, cattle, swine and sheep. Goats and sheep can graze on poison hemlock with no ill effects. Some insects may feed on the plant as well. But animals generally avoid poisoning themselves by not consuming toxic plants.

What does poison hemlock do to the body?

The toxic alkaloids in poison hemlock attack the central nervous system. Symptoms appear within 30-90 minutes and include dilated pupils, increased heart rate, numbness, tremors, paralysis and respiratory failure in severe poisonings. Death can occur from respiratory paralysis.


Identifying and properly removing poison hemlock takes vigilance and persistence. Understanding the plant’s key characteristics, growth habits and methods of reproduction is the first step. Integrated management combining manual removal, repeated cutting/mowing, herbicide application and grazing allows for effective long-term control. With proper identification and removal techniques, poison hemlock can be eliminated to create safer spaces for people, pets and livestock. Being able to recognize this dangerous plant prevents accidental exposure to its toxins.