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Early Season Poison Hemlock Control

Poison hemlock is a difficult species of noxious weed that can be found commonly along roadsides, fencelines, and in vacant properties. But what is poison hemlock and how do you get rid of it? Let's start off with a few basics.


Poison Hemlock has several identifying features that set it apart from other look a-likes such as Queen Anne's Lace and Giant Hogweed. The best way to identify poison hemlock is by looking at its foliage and stems. The stem is the most important part of identification- it will be hairless and have red/purple splotches present towards the base, as opposed to Queen Anne's Lace which has a hairy stem and no red/purple splotches. The leaves also have a very particular shape, what is described as 'fern-like', and are not present on Giant Hogweed.

Poison Hemlock is a biennial, in its first year it will grow large rosette leaves lower to the ground, and during the Spring of its second year it will bolt up to 12-feet in height, flowering by the Summer.

If you have questions about identification contact OSU Extension Butler County at (513) 887-3722.

Poisonous Qualities

Poison Hemlock is just that - poisonous. Every part of the plant can cause physical harm, and even death for humans. Not only can it cause harm when it enters the body, many people have dermal reactions to it as well. One of the worst things a person can do is mow or weed whack over it and inhale the particulates, so if you do plan on mowing this plant, always wear a respirator and eye protection. There is no known cure for a Poison Hemlock infection, which makes this plant even more dangerous to humans. The best thing you can do is to know how to identify, eradicate, and to inform others, especially young children.


The best time to get rid of Poison Hemlock is when it's in its first year growing stage. There are several different recommendations depending on the severity of infestation. If you choose to eradicate by mowing or pulling be sure to wear proper protective equipment (PPE). If possible, something should be immediately planted to help subdue any potential seed bank that may be present. If there is a larger infestation then the recommended eradication method is to use an herbicide. Broadleaf herbicides may work best as they will only kill the poison hemlock and not any surrounding grasses. Be sure to positively identify suspected populations and spray carefully as to not damage any of the surrounding vegetation. Most importantly read herbicide labels carefully and completely, the label is the law!


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