Ageratina altissima, commonly known as white snakeroot, is a perennial herbaceous plant native to eastern and central North America. This species holds historical significance due to its toxicity, particularly to livestock, and its indirect role in the death of Abraham Lincoln's mother. White snakeroot is a member of the Asteraceae family, which includes daisies and sunflowers. This plant typically grows to a height of 1 to 5 feet, forming upright clumps. Its stems are smooth and often purplish or green. The leaves are opposite, simple, and ovate to triangular in shape, with serrated margins and prominent veins. They are typically 3 to 7 inches long and 2 to 4 inches wide, with long petioles. In late summer and fall, white snakeroot produces clusters of small, white, daisy-like flowers at the top of the stems. These flower heads are composed of numerous tiny florets and lack the ray petals characteristic of many other Asteraceae members. The flowers mature into small, dry fruits called achenes, each bearing a tuft of bristles (pappus) that aids in wind dispersal. White snakeroot thrives in a variety of habitats, preferring moist, shaded to partially shaded environments. It is commonly found in woodlands, forest edges, thickets, stream banks, and disturbed areas such as roadsides and old fields. Its native range extends across much of eastern and central North America, from southern Canada down to Florida and west to Texas and the Great Plains. While it prefers moist conditions, it can tolerate some drought once established. It is adaptable to various soil types, as long as they are well-drained. The primary ecological and historical importance of Ageratina altissima lies in its toxicity. The plant contains tremetol, a toxic alcohol that, when ingested by grazing animals, can cause a condition known as "trembles." If humans consume milk or meat from animals suffering from trembles, they can also be poisoned, a condition known as "milk sickness." This was a significant threat to early settlers in North America. Ecologically, white snakeroot serves as a nectar source for various pollinators, including butterflies and bees, during its late blooming period. It is also a host plant for certain insect larvae. While not typically cultivated for ornamental purposes due to its toxicity and somewhat weedy nature, its late-season blooms can add visual interest to naturalized gardens in appropriate settings. An interesting adaptation of white snakeroot is its ability to colonize disturbed habitats, often appearing in areas where the soil has been turned or where shade has been reduced. Its wind-dispersed seeds allow it to spread effectively into new areas. The plant's perennial nature, with its roots surviving the winter to send up new shoots in spring, contributes to its persistence in suitable environments.