White Snakeroot are upright or sometimes ascending, growing to 1.5 meters tall, producing single or multi-stemmed clumps. They are found in woods and brush thickets were they bloom mid to late summer or fall. The flowers are a clean white color and after blooming small seeds with fluffy white tails are released to blow in the wind.

This species is adaptive to different growing conditions and can be found in open shady areas with open bare ground, it can be weedy in shady landscapes and in hedgerows.

There are two different varieties Ageratina altissima var. angustata and Ageratina altissima var. roanensis (Appalachian white snakeroot); they differ in the length of the flower phyllaries and shape of the apices.

Toxicity

White Snakeroot contains the toxin tremetol and when consumed by cattle the meat and milk become contaminated. When milk or meat from cattle feeding on White Snakeroot is consumed by humans, the poison is passed onto humans and can result in tremetol poisoning called milk sickness (notably the cause of death of Nancy Hanks, mother of Abraham Lincoln).

It is also poisonous to horses, goats, and sheep. Signs of poisoning in these animals include depression and lethargy, hind feet placed close together (horses, goats, cattle) or held far apart (sheep), nasal discharge, excessive salivation, arched body posture, and rapid or difficult breathing.