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Watch for these toxic weeds on pasture

Droughty conditions could cause a spike in toxic weed pressure. Take some extra precautions to keep that from happening.

Allison Lynch, Indiana Prairie Farmer Senior Editor

October 29, 2024

3 Min Read
Poison hemlock is a common sight in pastures during dry conditions
EXPECT THIS: Poison hemlock is a common sight in pastures during dry conditions. Pull your animals off pasture if you see this plant, which features lacy leaves and red blotches on the stems.Tom J. Bechman

Not everything that is green in the pasture is good for your livestock. This becomes even more true under dry conditions, when undesirable plants start dotting the landscape.

The droughty conditions this fall could lead to an influx of toxic plants on pasture entering the winter months. This means it will be key to prevent growth of these plants and keep your livestock away from them should they start popping up in your pasture.

“With most poisonous plants in general, they don’t taste good, and most animals usually don’t eat them unless there’s nothing else for them to eat,” says Bill Johnson, a Purdue Extension weed control specialist. However, this fall and early winter could pose a scenario where there is nothing else to eat if dry conditions persist.

Top three

There are three main plants to keep an eye on as we enter the colder months: poison hemlock, white snakeroot and perilla mint. Here is how to identify them:

Poison hemlock. This plant is often confused with common ragweed, with lacy, dark-green leaves. However, the stems are hairless and covered with red blotches.

“Poison hemlock really seems to take off when we have dry weather conditions,” Johnson says. He shares that you are almost guaranteed to see poison hemlock across the state when it’s dry.

Related:6 ways to reduce summer slump on pasture

Victor Shelton - Highly toxic white snakeroot has white flowers and hairless stems, with petioles attaching the leaves to the stem

White snakeroot. This plant has white flowers in clusters, as well as a hairless stem and petioles connecting the leaves to the stem. White snakeroot largely poses a risk to cattle and horses, and it can be found near wooded areas. Additionally, Johnson shares that the poison from this plant can be passed through milk from lactating animals to humans.

Victor Shelton, a retired agronomist/grazing specialist with the Natural Resources Conservation Service, says that he already has been called to examine a handful of sites this year where this plant is present. Johnson adds that this plant likely will be more prevalent in southern Indiana.

Perilla mint. This plant is identified by its broad leaves, shaped like ovals or hearts with serrated edges. It also has square stems, small tubular flowers and a strong minty scent. Often, it is found around wooded areas. Johnson shares that perilla mint is still new to the Midwest.

Victor Shelton - Perilla mint has broad leaves, square stems and a minty scent can pose a threat to your livestock

Proper management

The largest piece of management advice to prevent this scenario is pulling livestock off pasture before they have the chance to overgraze.

“It’s better to protect forage plants and livestock by pulling them off pasture and feeding hay,” Shelton says.

If you find yourself in a situation where these toxic plants are already present, Johnson recommends consulting the Purdue Extension weed-control guides. There, you can find weed response tables that will walk you through how to best control those plants.

Related:Be wary of overgrazing pastures this fall

“The big thing is to pay attention to the animals, identify the weeds, and then utilize the resources out there — the Extension weed-control guide or the weed-control guides the industry publishes,” Johnson says.

About the Author

Allison Lynch

Indiana Prairie Farmer Senior Editor, Farm Progress

Allison Lynch, aka Allison Lund, worked as a staff writer for Indiana Prairie Farmer before becoming editor in 2024. She graduated from Purdue University with a major in agricultural communications and a minor in crop science. She served as president of Purdue’s Agricultural Communicators of Tomorrow chapter. In 2022, she received the American FFA Degree. 

Lynch grew up on a cash grain farm in south-central Wisconsin, where the primary crops were corn, soybeans, wheat and alfalfa. Her family also raised chewing tobacco and Hereford cattle. She spent most of her time helping with the tobacco crop in the summer and raising Boer goats for FFA projects. She lives near Winamac, Ind.

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