Poisonous Plants of the Southern United States

whitesnakeroot.jpg (59678 bytes)white snakeroot
Eupatorium rugosum

Perennial herb, .6 to 1.5 m tall, with erect branched or unbranched stems arising from a mat of fibrous roots. Leaves opposite, simple, ovate, 3.5 to 17 cm long, 2.5 to 11 cm wide, crenate to serrate. Flowers showy, white; borne in open, terminal clusters, blooming late in summer or fall. Easily confused with near relatives that are not poisonous. Positive identification requires the services of a trained botanist. Probably found in all southern states east of the Mississippi River except perhaps Mississippi but rare in the southern portion of the region and in lower elevations; rich, moist, open, deciduous woods or bordering streams.


The toxic principle has been identified as an alcohol called tremetol. It is found in all parts of the plant whether green or dry. All domestic livestock, some laboratory animals, and human beings are all susceptible to the effects of this plant. Animals may be poisoned from consuming the actual plant or from ingesting milk from cows, sheep or mares that have eaten the plant. Drinking milk from cows eating white snakeroot has accounted for illness called "milk sickness" and for deaths in humans.


Trembling is the most commonly observed sign. The condition has been called "trembles." Animals are stiff and sluggish, stand with feet wide apart and may eventually become recumbent. Slobbering, vomiting, constipation and dribbling of urine are also seen. A ketone odor may be detected on the breath. Humans may exhibit delirium after drinking toxic milk.


Laxatives may be of benefit but there is no specific treatment.


commonsneezeweed.jpg (55795 bytes)common sneezeweed
Helenium autumnale

Clump-forming, perennial herb from a crown,.5 to 2 m tall. Leaves alternate, simple, elliptic to lanceolate, serrate to almost entire, 6 to 15 cm long, 1 to 3 cm wide; bases of leaves continuing as lines down the stem. Flowers yellow; borne in conspicuous heads. Found throughout the south but less common in coastal plain; moist places in pastures, bogs and ditches.


The toxic principle is a glucoside, dugaldin, and a phenol. Sneezeweed appears to cause more severe signs than does bitterweed. In the Rocky Mountain area, sheep have been severely poisoned by consumption of all portions of the sneezeweed plant. Cattle may also be affected but require a much larger amount.

The plant retains its toxicity even after drying, therefore, heavily contaminated hay can cause problems. Most cases occur when animals are on summer pasture and other forage is not available.


Sneezeweed is a severe irritant to the mucous membranes. Dullness, trembling and weakness are first observed. In many instances, vomiting is prominent. For this reason, it has been called "spewing sickness" by sheepmen. Many vomiting animals inhale part of the regurgitated material into the trachea and develop inhalation pneumonia. These animals usually survive only to become chronically poor performers and perhaps die later from secondary ailments.

Bitterweed can cause similar problems under experimental conditions. Cattle consume bitterweed only if other forage is unavailable


There is no effective treatment

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