Veterinary Medicine Library

White Snakeroot (Eupatorium rugosum Hout.)
(formerly known as Eupatorium urticaefolium)

| Description | Distribution | Conditions of poisoning | Control | Toxic principle | Clinical signs | References

white snakeroot


White snakeroot is an erect, branched herb usually about 3 feet tall but varying from 1 to 5 feet. It has slender, round stems and branches bearing pointed, oval, oppositely placed leaves. These leaves, 3 to 5 inches long and petioled, are sharply toothed on the margins. Each leaf has 3 main veins that show prominently on the underside. The roots are fibrous, coarse, and shallow.

White Snakeroot (early growth) White Snakeroot in bloom
   Early growth     With flowers

In late summer, numerous small heads of minute white flowers appear at the top of the stem and the ends of the branches. These flower heads, except that they are white, are almost exactly like the flower heads of the familiar ageratum of gardens. Later the flowers are replaced in the heads by small black seeds each with a crown of soft white hairs.

Because the leaves of white snakeroot resemble those of the nettle, other plants with nettle-like leaves are often mistaken for it. Two such plants are the nettle-leaved sage and the nettle-leaved vervain. Even without flowers or fruit, these plants can be easily distinguished from white snakeroot. The nettle-leaved sage, a rare plant in some southern Illinois counties, has square stems; white snakeroot stems are round. The nettle-leaved vervain, a common weed throughout Illinois, has lance-shaped leaves; white snakeroot leaves are broad at the base but narrow quickly in a wedge-shaped part to the petiole.


White snakeroot is found in woods of all types and along streams in wooded pastures throughout the Midwest. It persists after woods are cut, and often may be found many years after the land has been cleared, although usually in such areas it occurs only as scattered unthrifty plants. In prairie regions, it is not often found except in the woods bordering streams.

Conditions of poisoning

An animal may die from eating either a large amount of white snakeroot at one time or small amounts over a long period. The eating of small quantities more or less continuously gives rise to the animal disease known as trembles. It is also the cause of the well-known and much-feared milk sickness of man -- a disease that is contracted from drinking milk or eating milk products from poisoned cows. Milk sickness claimed thousands of lives in the early 1800s, perhaps the most well-known victim being Abraham Lincoln's mother. Nursing calves and lambs may die from their mothers' milk contaminated with snakeroot even though the mother animals show no signs of poisoning. Cattle, horses, and sheep are the animals most often poisoned.


During the dry period of late summer, animals should not be pastured in woods or fields where there is white snakeroot. If the pasture is known to be infested, animals should be moved out of it within the first few days of July and should not be returned to it until the following year.

Eradication of white snakeroot is not easy. Chemical weed-killers cannot be used satisfactorily, because they endanger trees and other plants of the pasture. The best way to reduce the number of the plants is to pull them out by the roots and burn them; the best time to do this is in September, when the plants are more easily identified by their white blossoms. If the plants are pulled after a hard rain while the ground is soft, the shallow roots come out readily.

Toxic principle

Clinical signs

White snakeroot can endanger the lives of persons and animals other than those that have actually eaten the plant.

Other References:

White Snakeroot entry in Wikipedia

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