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This herbaceous perennial grows 1 to 3 feet tall with flat-topped panicles of brilliant white flowers that bloom from late July through October (the genus name is based on Greek words for “unaging”).  It adapts to a variety of soils, although it prefers rich, loamy soils with some moisture.  In the wild, it grows in shadier conditions and does not tolerate intense sun or drought.  A member of the aster family, white snakeroot lacks the daisy-like appearance of many familiar asters.  Instead, the small flower heads have up to 30 petite, tubular florets with white corollas surrounded by white pappi, or bristles, which give the flower heads a fuzzy appearance.  The flower heads occur in clusters at the tops of branches.  Each plant may have one or many erect stems that branch out near the top.  Pairs of branches ascend from the stems at an angle of about 45 degrees, displaying a mist of delicate, white flowers. The plant is loosely dressed in large, heart-shaped leaves that get smaller and more lance-like as they ascend. In spring, the leaves are easy to identify when Liriomyza eupatoriella, a leaf miner insect, uses them as a host for its larvae, which tunnel through the foliage and leave winding trails in their wake.  

 

White snakeroot’s leaves and stems contain tremetol, which is toxic to animals and humans.  Deer will not touch the plant, but cattle, goats, horses, and other livestock species have been poisoned by it.  “Milk sickness” used to be a common cause of death among 19th-century settlers (including Abraham Lincoln’s mother) who drank the tainted milk of poisoned animals.  Anna Pierce Hobbs Bixby, a frontier physician, learned about the plant’s toxicity from a Shawnee woman.  Bixby, whose own mother died from milk sickness, was instrumental in removing the plant from her community, but milk sickness occurred elsewhere until the 1920s.

 

White snakeroot resembles many white-flowered bonesets and thoroughworts, but white snakeroot has broader leaves, and its lower leaves are heart shaped with long petioles.  It also grows in shady woodlands, whereas the other species are found on sunnier sites.  

 

Native habitats include woods, roadsides, fields, thickets, under powerline clearances, and shady corners of pastures and yards.  Snakeroot spreads by rhizomes and seeds to form dense stands in woods and naturalized areas.  The plant is often used in cottage and rock gardens, water or rain gardens, woodland areas, and shady corners of borders.  

 

Plant Characteristics:

Grows 2-3’ tall and 2-4’ wide.

 

Prefers part to full shade.  Will grow less aggressively in sunny locations.     

 

Does best in moist to slightly dry, loamy soils but adapts to clay and chalky soils.

 

Each flower head is ½” across and has 10-30 disk florets with white, tubular, five-lobed corollas and long, divided styles.  Each disk floret is replaced by a black, elongated achene with a small tuft of white hairs for wind dispersal.  

 

Dark green leaves are mostly hairless and have coarsely serrated edges, round bases, and pointed tips.  They are arranged opposite on tan to light green stems.  

 

Wildlife Value:

Host plant to 7 species of Lepidoptera larvae, including clymene moth, dusky groundling, and eyed thyris.  The nectar attracts wasps; various flies; butterflies; moths; and many bees, including leafcutters, bumbles, small carpenters, honey, and halictids. The bees also collect pollen.  Songbirds eat the seeds.  

 

Medicinal, Edible, and Other Uses:

A root tea was used to treat diarrhea, kidney stones, and fever.  It was thought that burning fresh snakeroot leaves would produce smoke that was able to revive the unconscious.

 

Caution: Using snakeroot for medicinal purposes is not recommended.

Snakeroot, White, Ageratina altissima

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