Poison Hemlock - Ask Extension
We have discovered poison hemlock on a back part of our yard. How do we get rid of it safely?
Knowledgebase
Poison Hemlock #793862
Asked June 02, 2022, 2:01 PM EDT
We have discovered poison hemlock on a back part of our yard. How do we get rid of it safely?
Logan County Ohio
Expert Response
Hello,
Poison hemlock is a biennial, which means during year one it forms a basal rosette (usually very large) and the second year it flowers. The plant is highly toxic if ingested so take great care when handling all parts of the plant. Protective clothing and eye covering should be worn at all times and care should be taken not to touch your face while working with the plant. Poison hemlock will not cause a skin rash; a similar-looking and related plant, wild parsnip - which has yellow flowers, can cause severe skin reactions.
Since these plants are already starting to flower it’s very important to remove the flowers and dispose of them in the trash. Do not leave flowers lying on the ground or put them in yard waste or compost as the flowers could still form seeds even after they are cut off.
Similarly, at this stage in its development herbicide will not be effective as the flowers will continue to develop and form seeds before the herbicide will kill the plant.
If you identify other poison hemlock plants in their first year of development (basal leaves only) you can spray these with herbicide or dig them up but watch the area very carefully this season for continued flower development.
If this is a small population of poison hemlock you may very well be able to control it in one year with these treatment suggestions, but you should continue to monitor the area in subsequent years for new plants as there could still be ungerminated seed in the area. It’s possible that there is poison hemlock growing unchecked in a nearby area where the seed originated so you should continue to monitor all areas of your property to catch new plants in their first year of development.
If the poison hemlock covers a large area, you may need to hire a professional to apply the proper type and amount of herbicide to control it. However, this treatment should be done only on first year rosettes or early next spring (March or April) as soon as the leaves appear. Once the plant flowers, it is too late for herbicide treatment to be effective.
In my personal experience removing a single poison hemlock plant, I was able to cover the plant with a large garbage bag, dig it out, and invert and tie up the garbage bag, thereby avoiding any contact with the plant,
If you choose to apply herbicide, be sure to follow all label instructions carefully and do not use a chemical for an application not specifically listed on the label.
This article from Ohio State provides more information on poison hemlock and wild parsnip. Note that the article is from March of this year; the most effective time of the year to deal with either of these non-native plants.
https://bygl.osu.edu/node/1935
Poison hemlock is a biennial, which means during year one it forms a basal rosette (usually very large) and the second year it flowers. The plant is highly toxic if ingested so take great care when handling all parts of the plant. Protective clothing and eye covering should be worn at all times and care should be taken not to touch your face while working with the plant. Poison hemlock will not cause a skin rash; a similar-looking and related plant, wild parsnip - which has yellow flowers, can cause severe skin reactions.
Since these plants are already starting to flower it’s very important to remove the flowers and dispose of them in the trash. Do not leave flowers lying on the ground or put them in yard waste or compost as the flowers could still form seeds even after they are cut off.
Similarly, at this stage in its development herbicide will not be effective as the flowers will continue to develop and form seeds before the herbicide will kill the plant.
If you identify other poison hemlock plants in their first year of development (basal leaves only) you can spray these with herbicide or dig them up but watch the area very carefully this season for continued flower development.
If this is a small population of poison hemlock you may very well be able to control it in one year with these treatment suggestions, but you should continue to monitor the area in subsequent years for new plants as there could still be ungerminated seed in the area. It’s possible that there is poison hemlock growing unchecked in a nearby area where the seed originated so you should continue to monitor all areas of your property to catch new plants in their first year of development.
If the poison hemlock covers a large area, you may need to hire a professional to apply the proper type and amount of herbicide to control it. However, this treatment should be done only on first year rosettes or early next spring (March or April) as soon as the leaves appear. Once the plant flowers, it is too late for herbicide treatment to be effective.
In my personal experience removing a single poison hemlock plant, I was able to cover the plant with a large garbage bag, dig it out, and invert and tie up the garbage bag, thereby avoiding any contact with the plant,
If you choose to apply herbicide, be sure to follow all label instructions carefully and do not use a chemical for an application not specifically listed on the label.
This article from Ohio State provides more information on poison hemlock and wild parsnip. Note that the article is from March of this year; the most effective time of the year to deal with either of these non-native plants.
https://bygl.osu.edu/node/1935
