Common Poisonous Plants

Roger High, OSU Ohio State Sheep Extension Specialist

While most plants are beneficial, some are hazardous to animal and human life. Ohio has about 100 toxic plants and some of these are responsible for deaths of domestic livestock every year. The number of cases of toxicosis (plant poisoning) in livestock far outweighs those reported for humans. Accurate statistics are not available, but it is estimated that several thousand animals die annually in the U.S. from plant toxicosis.

With houses springing up everywhere in Ohio, the rural/urban interface is dramatically increasing. Many farm neighbors are unfamiliar with the plants that are toxic and many of them are found in our home landscapes. Homeowners bordering farmland or pastures should not throw yard waste over the fence or onto cropland without consulting the farmer or landowner.

The following are some common plants that are poisonous to farm animals:

Garden Iris
Grown as an ornamental plant, the iris contains an irritant in the leaves or root stalks which can produce gastroenteritis if ingested by livestock in sufficient amounts.

Common holly, a favored ornamental in landscapes around the home, has berries that are poisonous and cause vomiting, diarrhea, and stupor in animals if ingested in large amounts.

Morning Glory
Hogs, sheep, cattle and goats are especially susceptible to poisoning from overdoses of the hallucinogenic seeds produced by the morning glory.

Bracken Fern
This plant is poisonous in a fresh or dried condition causing rough hair coats, listless attitudes, and mucous discharge in ruminant animals like sheep, cattle, and goats. Elevated temperatures, swelling of the neck and difficult breathing may occur. Monogastrics, like swine, may show anorexia and incoordination.

The flat leaf blade is the toxic part of the rhubarb plant that causes staggering, excessive salivation, convulsions, and death in most classes of livestock.

English Ivy
All species of livestock have exhibited toxicosis from English Ivy with symptoms including local irritation, excessive salivation, nausea, excitement, difficult breathing, severe diarrhea, thirst, and coma.

Wild Cherry
As far as plants go, wild cherry is probably the most common cause of livestock poisoning known. The most common exposure occurs when limbs are blown down or are trimmed and thrown into a fenced area. Only the wilted leaves are toxic as they produce cyanide. Wilted cherry tree leaves cause anxiety, staggering, falling down, convulsions, rolling of the eyes, tongue hanging out, loss of sensation, and dilated pupils. The animal then becomes quiet, bloats and dies within a few hours of ingestion.

This popular, needlelike shrub grown around the home contains poisonous alkaloids. Symptoms of yew poisoning are gastric distress, diarrhea, vomiting, tremors, dilated pupils, respiratory difficulty, weakness, fatigue, collapse, coma, convulsions, circulatory failure, and death.  Survival after yew poisoning is rare.

Acorns and young shoots can cause severe poisoning especially if eaten in quantity. Cattle, sheep, horses, swine will display anorexia, constipation that develops into diarrhea, gastroenteritis, thirst, and excessive urination.

Mountain Laurel
Native or wild Mountain Laurel, Rhododendron and Azalea are all considered poisonous and highly toxic to ruminants. Symptoms of poisoning include: anorexia, repeated swallowing, profuse salivation, watering of the mouth, eyes, and nose, loss of energy, slow pulse, low blood pressure, incoordination, dullness, and depression. Death is proceeded by coma.

Editors note: It pays in the long run to periodically check pastures and around the fence lines for plants that are toxic and remove them.

Adapted from an article by:
Chester D. Hughes, Extension Agent – Livestock, Penn State University

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