White Snakeroot (Ageratina altissima), also known as White Sanicle or Tall Boneset, is a poisonous perennial herb in the family Asteraceae, native to eastern North America. An older binomial name for this species was Eupatorium rugosum, but the genus Eupatorium has undergone taxonomic revision by botanists and a number of the species once included there have been moved to other genera.
Plants 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.
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.
An asexual propagated cultivar, sold under the name Eupatorium rugosum
'Chocolate', is grown in gardens for its dark tinted foliage. The darkest color, which is a chocolaty black, occurs in a sunny position, the plants grow best in moisture retentive soils and are shade tolerant. More recently the plant can be found under the correct species name and is listed as Ageratina altissima