Poison Hemlock: Timing our control methods to have the biggest impact

Written by Jacob Luken
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Why is Poison Hemlock Important?
Poison Hemlock (Conium maculatum) is a particularly harmful noxious weed belonging to the carrot family that shades out native plants, chemically alters the soil, and is notoriously toxic to humans and livestock.

When Can I Control Poison Hemlock?

• March is the best time to remove Poison Hemlock by pulling it and spraying it with the appropriate herbicides
• Hemlock can be treated almost as soon as it sprouts
• Once Poison Hemlock flowers are in full bloom (see picture below) it is too late to treat for the season. The first flowers usually start to show in June, but keep your eye out for new sprouts throughout the summer.

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​How Do I Control Poison Hemlock?

• Mechanical – Poison Hemlock has a deep taproot (see right) that develops quickly, but if you spot it before the plant is more than a foot or two tall, you can pull or dig the plant up. It’s important to wear gloves and long sleeves to protect your skin as well as make sure you get the entire root up when you pull it to ensure control.

• ​Chemical – Chemical control is most effective for large or dense patches of Poison Hemlock. By using a hand-held sprayer, backpack style sprayer, or other chemical spray applicators you can cover a wide area with a fine mist of herbicide. This targeted spray technique is most on sunny days with temperatures over 55° Fahrenheit and spraying in March before native plants start popping up helps to minimize overspray.

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​Native Look-Alikes
As a member of the carrot family, Poison Hemlock bears a strong resemblance to other native or common species in Indiana such as Queen Anne’s Lace, Purple-Stemmed Angelica, and Spotted Water Hemlock.

​Read more here to learn more about how to identify, remove, and protect yourself from Poison Hemlock. If you are a Hamilton County Resident and have more questions or are unsure if you have Poison Hemlock on your property, call or email our office to receive our free technical services.