Source: J.D. Green, extension weed scientist

In about a month, many of you will begin cutting your first hay of the season. While making hay, it is important for you to notice and remove poison hemlock from your hay or pasture fields.

Native to Europe, poison hemlock is an invasive weed that was introduced as an ornamental in the United States during the 1800s. It is potentially poisonous if ingested by livestock or humans in both its vegetative growth stages and when dry. The weed is often found along fencerows, roadways and other areas not used for cropland across most of Kentucky and the United States. However, in the past several years, its presence has increased across Kentucky, and it is now found in some hay and pasture fields.

If consumed, poisoning symptoms appear rather quickly in livestock and include nervousness, trembling, muscle weakness, loss of coordination, pupil dilation, coma and eventually death from respiratory failure. Livestock usually do not eat poison hemlock when in its natural growing state because of its unpalatable taste. However, they will eat it if no other forage is available or when they inadvertently consume it through hay.

Ideally, you should control poison hemlock with herbicide products applied during the plant's early vegetative growth stage during the late winter or early spring or with an herbicide treatment in the fall. By this time of the year it may now be too late for effective control with 2,4-D applied alone and may require other herbicide options for best control. With herbicide applications to grazed pastures remove livestock from the field until plants have fully died. You can also control poison hemlock by mowing or mechanically removing the plant before it produces new seeds, which occurs soon after flowering. If you find it while cutting hay, either mow around the weed or mow it separate from your stored hay.

The easiest way to identify poison hemlock is by its smooth, purple-spotted stem. Poison hemlock is often confused with the nontoxic weed Queen Anne’s Lace (also called Wild Carrot) because both produce clusters of small, white flowers but Queen Anne’s Lace will have hairs along its stem and leaf bases. Poison hemlock usually reaches its peak bloom in late May or early June, while Queen Anne’s Lace blooms a little later in late June and July.

For more information on controlling weeds in pastures, contact the (COUNTY NAME) office of the University of Kentucky Cooperative Extension Service.

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