Common Names

The white snakeroot is also known by the names white sanicle, Indian sanicle, squawweed, richweed, white top, and deer-wort-boneset.


This attractive, slender perennial of the woods grows to a considerable height and affords a supply of rich, green herbage in the late summer and autumn. The leaves are placed opposite one another on slender stalks. They are from three to six inches long and from one to three inches wide, ovate, thin, sharply pointed at the apex; rounded, straight or sometimes heart-shaped at the base. Their margins are coarsely and usually sharply toothed, sometimes varying to round-toothed. The inflorescence is rather loose and open. Each flowering head, consisting of from ten to thirty bright white flowers, is about a quarter of an inch wide and slightly longer, somewhat bell-shaped.


Snakeroot is found in rich, damp woods or on the borders of open woods in Canada from New Brunswick to Ontario. Sometimes it grows in abundance on hillsides and lately cleared land.

Poisonous Properties

Although it is apparent that white snakeroot is an unwholesome plant, very little is known of its chemical constituents. The earlier evidence of its connection with the disease known as "milk-sickness" is of a rather contradictory nature. Selby states that it is a "dangerous poisonous plant for Ohio, particularly in the more northerly districts. Animals which feed upon it, more especially cattle and sheep, are frequently seized by the disease known as 'trembles', often with fatal results. Persons who use the milk or butter from cows suffering from this disease are many times attacked by 'milk-sickness', at times with fatal results." He quotes from E. L. Mosely who made a chemical analysis of this plant and found considerable quantities of aluminum phosphate in the leaves. Moseley contends that the effect of feeding white snakeroot to various animals is identical with the symptoms of 'trembles'. On the other hand we have the report of A. C. Crawford as follows: "To sum up, it certainly cannot be said that it has been proved that milksickness is due to any constituent of E. urticaefolium. The transmission of the disease by eating small quantities of meat or milk of animals sick with the 'trembles,' and the fact that cooked meat or boiled milk does not produce this disorder, point primarily rather to a parasitic origin, while the fact that Eupatorium urticaefolium is abundant in areas where the disease is not known and absent in some milksick districts also indicates that the plant has no relation to the disease. If it does, it would be only an accidental carrier of some pathogenic organism. According to reports, the same flora may be in areas in which 'trembles' occur as in those free from it, and milk-sickness is also said to occur where no vegetation grows (inclosed pens). The disease also has disappeared from an area after simply clearing the woodland where it occurred and turning it into pasture. Again, severe epidemics have occurred in winter when the foliage has disappeared, which would tend to exclude the higher, non-evergreen plants as the cause of this disorder."

Plate XXXIX.

White Snakeroot.

Photo - F. Fyles.

White Snakeroot.

The later experiments however, of Curtis and Wolf, as well as those of Marsh and Clawson (1917) are conclusive in showing that, apart from the evident connection of milk-sickness with the symptoms caused by the ingestion of snakeroot, there is no doubt that this plant is poisonous to stock. The former says: . . . "white snakeroot had" previously been claimed by Moseley to cause trembles in animals. This claim has been substantiated by experiments with sheep in which green plants of E. ageratoides were fed"; and the latter: ". . . it has been clearly demonstrated that E. urticaefolium must be counted as one of the rather important stock-poisoning plants which produces serious losses of domestic animals." These experiments also showed that the plant loses a large part of its toxicity in drying.

In the following year, 1918, the experiments of Wolf, Curtis & Kaupp. in North Carolina, also proved that trembles and milksickness were due to this plant. According to them, the disease may appear "at any season of the year, but is most prevalent in late summer and autumn, especially when other vegetation is scarce because of drought. The disease is frequently fatal in domestic animals while the sequel of milksickness in man, in case of recovery, is lasting debility." "During the experimentation, 31 fatal cases of trembles and milksickness have been developed among the 44 ewes and lambs that were employed in some phase of the experimentation involving the feeding of white snakeroot. Two of these lambs contracted genuine cases of milksickness by suckling their mothers, demonstrating that the disease may be transmitted through the milk. This fact has for a long time been a matter of common belief among farmers. Furthermore, animals in lactation, having access to white snakeroot, may be apparently normal yet are capable of transmitting milksickness through their milk."

Animals Affected

The experiments referred to above proved that white snakeroot was poisonous to all domestic animals.


The action of the poison is cumulative. The general symptoms as given by Marsh and Clawson are, trembling, especially of the nose and legs, more marked after exercise; depression and inactivity; constipation with nausea and vomiting; pronounced weakness; difficulty in standing, the animals sometimes remaining down for a prolonged period before death.

Remedy And Means Of Control

As the plant produces an enormous quantity of small seeds it should not be allowed to reach maturity. Grubbing out or repeated cutting is the only effectual means of getting rid of this weed.