Poison hemlock is one of the most prevalent poisonous weeds across Ohio.
Photo courtesy of Ohio Country Journal
This time of year, I get a lot of calls in the office about poison hemlock in people’s pastures, forest edges, or ditches. Poison hemlock is one of the most prevalent poisonous weeds across Ohio. This weed is a biennial meaning that it completes its life over a two-year period, starting as a low-growing rosette in the late fall and bolting in the spring. The rosettes will overwinter and then begins growth again in the spring. After bolting, the weed will produce flowers and then seeds. Poison Hemlock can reach heights of eight feet tall. Poison Hemlock as the name suggests is poisonous and contains cyanide. This weed can kill livestock and other animals when eaten.
Landowners should understand that the larger a weed gets, the less effective herbicides are in controlling the weed. Many people ask what they should spray on the Poison Hemlock now that they finally notice it going to flower, my reply is that herbicides will be most ineffective at this stage of growth. Herbicides are most effective in killing Poison Hemlock in two stages and times. 1.) In the fall when plants are in young rosette form, 2.) Early spring before bolting. Right now, the best thing landowners can do to control poison hemlock is to mow them down and try to prevent seed spread.
Herbicide control recommendations can be found on table 21 of the Weed Control Guide for Ohio, Indiana, and Illinois. Herbicides rated 8 or 9 are the most effective in controlling poison hemlock. A few options include Crossbow, Remedy Ultra, Cimarron Max, Curtail, Dicamba, and Glyphosate. Mixing Dicamba and Glyphosate can improve control compared to applying one or the other individually. Remember that the herbicide label is a legal document and must be followed entirely. Weed Control Guides can be purchased from the Clinton County Extension Office. For more information about poison hemlock call the Clinton County Extension Office at 937-382-0901.
*Information used from the C.O.R.N Newsletter
