Poison hemlock is growing in Missouri this summer. How to identify and get rid of it

Joseph Hernandez
·4 min read

Don’t let the poison hemlock’s white spring flowers fool you when you come across it in the wild. The plant is highly invasive and dangerous, causing illnesses to people and animals that come into contact with it.

The poisonous plant blends in with nonpoisonous plants and grows all across Missouri, blooming from May until September, according to the Missouri Department of Conservation.

The plant takes two years to grow and produces up to 38,000 seeds per plant, University of Missouri Extension weed scientist Kevin Bradley wrote in a blog post. It’s one of the first plants to green up in the spring and can be found at roadsides, on edges of cultivated fields, along creekbeds, near irrigation ditches and in waste areas, the United States Department of Agriculture says.

Here’s what else you need to know about the poison hemlock.

WHAT DOES POISON HEMLOCK LOOK LIKE?

Poison hemlock grows from a center stalk and has light green stems and fern-like leaves that can grow up to 6 feet tall in Missouri’s climate. It forms umbrella-shaped clusters of 12-15 white flowers with five petals in the spring in its second year of growth.

Poison hemlock
Poison hemlock

HOW POISONOUS IS THE HEMLOCK?

Every part of the plant is poisonous. Poisoning can happen in humans from inhaling the plant’s fumes or through skin contact. Eating part of the plant can be fatal to humans. It’s more dangerous than poison ivy, which causes itching to a person’s body part if they touch the plant.

The plant is also toxic for animals, including cats, dogs and horses. Contact a veterinarian immediately or call the Pet Poison Helpline at 855-764-7661 if your pet shows signs of poisoning. Death can occur quickly.

HOW TO GET RID OF POISON HEMLOCK

If you find what you suspect to be poison hemlock on your property, get rid of it right away. There are two ways to get rid of hemlock: Dig it up or use herbicide.

If the hemlock is around other plants you don’t want to harm, it’s recommended to dig it up. While you’re removing the plant, you should wear long sleeves, gloves and eye protection, as every part of the plant is poisonous. When throwing the plant away, you should put it in a separate plastic bag and make sure to not burn it, as the smoke is dangerous.

If you’re using herbicide but want to protect the turf grass around the plant, Bradley recommends using 2-4-d-based herbicide or one with the active ingredient triclopyr.

“The key to control is applying the herbicide when plants are young and still in the rosette stage,” Bradley said in a blog post. “Mature plants do not respond to chemical control measures.”

WHAT PLANTS LOOK LIKE HEMLOCK?

Poison hemlock can get confused with other plants. Here are a few of its lookalikes and what you should know about them:

  • Queen Anne’s Lace/wild carrot: This edible and medicinal plant grows shorter than hemlock. Its stem has hairs, unlike hemlock’s smooth stem.

  • Yarrow: Edible and medicinal, it grows shorter than hemlock and has distinct frilly leaves.

  • Wild fennel: The plant is edible, and its flowers are yellow instead of white. Entire plant smells like anise or licorice.

  • Elderflower: Its flower blossoms are edible, with leaves that branch off in opposite directions, where hemlock leaves alternate.

  • Cow parsley: Edible, this plant grows shorter than hemlock. Stems are ridged, not smooth like hemlock, and hairs grow on underside of leaves.

The stems of poison hemlock have purple spots, which can help in identifying the plant.
The stems of poison hemlock have purple spots, which can help in identifying the plant.

WHAT SHOULD I DO IF I TOUCH HEMLOCK?

The Centers for Disease Control and Prevention says you should perform the following steps if you touch a poisonous plant like hemlock:

  • Rinse immediately with rubbing alcohol, poison plant washes or dishwashing soap and plenty of water.

  • Scrub under nails. Apply wet compresses, calamine lotion or hydrocortisone cream to the skin to reduce itching and blistering.

  • Take an antihistamine like Benadryl to help relieve itching.

  • Get medical help in severe cases, or if the rash is on the face or genitals.

  • Call 911 or go to a hospital emergency room if you have a severe reaction, such as swelling or difficulty breathing.

Symptoms of poison hemlock may include vomiting, sweating, dilated pupils, rapid heartbeat, dry mouth, high blood pressure, increased salivation, restlessness and confusion, according to the Cleveland Clinic.