Plants you don't want in the pasture

May 29, 2007|by JEFF SEMLER

The weather has been lovely although we could use a shower or two. Hay is being made at a furious pace and thousands of head of livestock are enjoying pasture.

As pasture questions go, after what grasses should I plant for pasture, what poisonous plants should I worry about in my pastures is a close second.

There is good news and bad news in the area of poisonous plants. There are many plants that can be poisonous. That is the bad news.

The good news is, in most cases, an animal would have to be starving to eat them. The other piece of good news is dilution is the solution to pollution.


In other words, if your animal would happen to get a bite of the plant, all the other good plants it eats lessens or eliminates the issue.

While the list is long, most plants are not a concern. If you want an extensive list go to

This site belongs to the University of Pennsylvania vet school and is loaded with information.

The two most dangerous plants for us to be concerned about regardless of specie are Wild Cherry and Japanese Yew.

Japanese Yew is a common landscape plant. Livestock rarely come in contact with it on their own. The common source of Yew poisoning is a well-intentioned neighbor. They trim their shrubs and throw the clippings into a pasture field as a treat for the stock. Unbeknownst to them, Yew is extremely poisonous and the next day, the stock owner encounters dead animals.

So if you want to be a good neighbor, put your landscape trimmings in your compost pile or take them to the landfill where they can be composted with other plant material from across the county.

Wild Cherry, on the other hand, grows everywhere - in fence rows and fields. This tree is of no concern on most days. However as we approach thunderstorm season, we need to monitor our cherry trees.

Broken limbs with wilted leaves are extremely toxic to animals. Not green leaves on the living tree nor brown leaves in the fall, it is the wilted leaves from situations like storm damage.

I am often asked, should I cut down all my cherry trees?

The answer is yes unless you are going to walk your pastures immediately after a storm. It makes good firewood and if it is large enough, it makes beautiful lumber for woodworking.

For horse owners, there is one more tree of concern and that is the Red Maple. For the record, Red Maples have green leaves, so if you have a Crimson Maple or some of the other varieties with the red leaves, give your chainsaw a rest.

Red Maple is a typical maple with opposite simple leaves. The leaves are broad and have three to five lobes with palmately arranged veins. The fruit is a two-winged, two-seeded structure; the wings form a "V" and the two seeds lie at the bottom of the V. Twigs, buds, and flowers are reddish but the leaves are green. It is common to have groups of buds on side leaf scars (characteristic of red maple). Young trunk bark is smooth and gray; older bark is broken and dark. Height is 20-40 feet; diameter 1-2 feet.

Fresh, wilted and dried leaves are toxic and ingestion of as little as 0.3 percent of the body weight as leaves is toxic to horses.

Clinical signs are typical of acute hemolytic disease: depression, icterus, anemia, hemoglobinemia and hemoglobinuria. Polypnea and tachycardia may result from severe anemia and cyanosis may also be present.

Laboratory diagnosis of blood reveals a low packed cell volume (PCV), mild methemoglobinemia, Heinz bodies, hyperbilirubinemia and, sometimes, increased creatine phosphokinase.

Lesions are consistent with damage caused by hemolysis and hypoxia. The kidneys, spleen, liver and adrenal glands can be affected. Treatment is completely supportive, because there is no antidote.

Prevention is the best medicine. Do not plant Red Maples near horse pastures. Remove existing Red Maples in or near pastures.

The moral to this story is caution not panic. Walk your pastures and remember most plants are not a problem, just a nuisance.

Jeff Semler is an Extension educator, specializing in agriculture and natural resources, for the University of Maryland Cooperative Extension. He is based in Washington County. He can be reached weekdays by telephone at 301-791-1404, ext. 25, or by e-mail at

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