Ageratina altissima
Common names: white snakeroot, richweed, white sanicle; also known as Eupatorium rugosum
Description: herbaceous perennial
Native regions and distribution: eastern and central North America
Urban habitat: shady areas with open bare ground
Ecological function: host to many species of butterflies, bees, wasps, and flies and is the larval host to several varieties of moths. The plant is host to insect galls, which are highly distinctive plant structures formed by some herbivorous insects as their own microhabitats. The species is hermaphrodite (has both male and female organs) and is pollinated by insects.
History: The plant has been widely used medicinally by native American peoples. The Cherokee used it to as a diuretic, and to treat diarrhea, urinary diseases, and fever. The Iroquois used it to treat venereal disease, snakebite, and also used it ceremonially. The Chickasaw and Choctaw used it to treat toothache and the Meskwaki used it as a stimulant and as a steaming agent in sweatbath. Ageratina altissima contains the toxin tremetol; when the plants are consumed by cattle, the meat and milk become contaminated with the toxin. When milk or meat containing the toxin is consumed, the poison is passed on to humans. If consumed in large enough quantities, it can cause tremetol poisoning in humans. The poisoning is also called milk sickness, as humans often ingested the toxin by drinking the milk of cows that had eaten snakeroot. Although 80% of the plant's toxin, tremetone, decreases after being dried and stored away for 5 years, its toxic properties remain the same. During the early 19th century, when large numbers of European Americans began settling in the plant's habitat, many thousands were killed by milk sickness. Notably, milk sickness was possibly the cause of death in 1818 of Nancy Hanks Lincoln, mother of Abraham Lincoln. In addition to cattle, the plant is also poisonous to horses, goats, and sheep.