Plants & Weeds Toxic to Horses

— Written By N.C. Cooperative Extension
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This is a listing of the most commonly found toxic weeds in horse pastures in Burke County and is not all-inclusive. For example, Carolina jessamine, one of the most dangerous plants in North Carolina, is not listed because it does not occur in Burke County or the western areas of the state. In most cases, the weeds are unpalatable and will not be grazed unless desirable forages are unavailable. The notable exceptions are black cherry and red maple leaves. These leaves are toxic in even small amounts. A horse will sometimes eat the wilted leaves from a blown down black cherry and a few fallen red maple leaves can easily be picked up when grazing. A few years ago three horses died in Burke County when their owner fed their hay under a red maple during leaf drop. Some of these plants may surprise you and you will probably despair of ever learning them all. But learning them all is not the point. Your stock are living in a dangerous environment and the best way to protect them from toxic weeds is to develop and utilize a comprehensive weed control program. Such a program that involves both mowing and herbicides. Depending on mowing alone will result in a prevalence of perennial weeds while reliance on herbicides alone will develop an annual weed problem. A dual approach is best. Poisonous Weeds Toxicity Level Alfalfa (when blister beetles are baled in it) Dangerous!! Annual Buttercup Widespread, but of minor importance Arbovitae Dangerous, but uncommon Bitterweed or bitter sneezeweed Dangerous!!

Poisonous Weeds Toxicity Level
Alfalfa (when blister beetles are baled in it) Dangerous!!
Annual Buttercup Widespread, but of minor importance
Arbovitae Dangerous, but uncommon
Bitterweed or bitter sneezeweed Dangerous!!
Black cherry (when stressed) Dangerous!!
Black locust Dangerous!!
Black nightshade Dangerous!!
Black Walnut Dangerous, but rarely eaten
Bladderpod Dangerous, but rarely eaten
Bleeding heart Dangerous, but rarely eaten
Bloodroot Dangerous, but rarely eaten
Boxwood Dangerous, but generally unavailable
Braken fern Dangerous!!
Buckeye Dangerous!!
Buttonbush Dangerous, but rarely eaten
Camas, death camas, black snakeroot Dangerous, but rarely eaten
Castorbean Dangerous, but generally unavailable
Cedars Slight
Chinaberry Minor importance
Climbing bittersweet Minor importance
Cocklebur Dangerous!!
Corn Cockle Dangerous, but rarely eaten
Crotalaria Dangerous!!
Dogbane Dangerous!!
Elderberry Dangerous, but rarely eaten
False Hellebore Dangerous, but rarely eaten
Fumewort Dangerous, but uncommon
Ground cherry Dangerous, but rarely eaten
Horsenettle Dangerous, but rarely eaten
Horsetail or scouring rush Dangerous, but rarely eaten
Hydrangea Dangerous, but uncommon
Jimsonweed Dangerous!!
Johnsongrass (when stressed) Dangerous, but rarely eaten by horses
Lily-of-the-Valley Dangerous, but uncommon
Mayapple or mandrake Dangerous, but rarely eaten
Milkweed Dangerous, but rarely eaten
Milo (Grain Sorghum) (when stressed) Dangerous!!
Mistletoe Minor importance
Monkshod Dangerous, but uncommon
Mountain Laurel Dangerous!!
Oak Leaves and Acorns Minor importance
Oleander Dangerous, but uncommon
Perilla Mint Minor importance
Pigweed Dangerous, but rarely eaten
Pines Slight
Poison hemlock Dangerous, but rarely eaten
Pokeweed Dangerous!!
Rattlebox Dangerous
Red Maple (stressed leaves) Dangerous!! but rarely eaten
Rhododrendron Dangerous!!
Scarlet pimpernel Dangerous, but rare
Scott’s broom or scotch broom Minor importance
Sesbania Dangerous, but uncommon
Smartweed Minor importance
Sorghum and sudangrass hybrids (when stressed) Dangerous
Spruce Minor importance
Spurge Minor importance
St John’s Wort Minor importance
Staggergrass Dangerous!!
Star-of-Bethlehem Dangerous, but uncommon
Sweetshrub (Sweet Bubby) Dangerous, but rarely eaten
Sweet Clover (when frosted or baled wet) Minor importance
Tall fescue(endophyte) Moderately toxic problems common
White Snakeroot Dangerous!!
Wild parsnip or spotted cowbane Dangerous!!
Yew Dangerous, but uncommon
Wooly croton Minor importance

Associated Toxicities of Some Pasture Plants Red Clover Black patch fungus on leaves causes slobbers. In horses, it can cause dehydration to a life-threatening degree. This fungus is also found quite often on white clover types and should be suspected anytime excessive slobbering is observed in the horse. Sudangrass or Sorghum Can cause cystitis syndrome when grazed after a prolonged drought or heavy frost. While these compounds break down in hay in a matter of a few weeks these forages are still not recommended for horse hay due to the difficulty in drying down the thick stems and the attendant risk of the hay molding in the bales. Nitrates Can cause poisoning and death in heavily fertilized grass pastures and hay fields, especially in drought conditions. German Millet When fed as a major forage can cause kidney, joint and bone problems, especially when plants are mature. Lush pastures Horses unaccustomed to lush pasture can colic or founder if suddenly changed to them. Tall fescue Tall fescue is our most common pasture grass and hay species primarily because of its resiliency and low maintenance. A large measure of these benefits can be attributed to the presence of an endophyte fungus living in a symbiotic relationship within the plant. The fungus also produces an alkaloid which causes a number of problems for cattle and bred mares.

Updated on May 11, 2018
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