Above: White Snakeroot along shore of Ho-Nee-Um Pond in Madison, Wisconsin on August 21, 2019.
White Snakeroot - Ageratina altissima (Potentially invasive)
White Snakeroot is a hazardous native plant that grows from 1'- 5' tall. White Snakeroot prefers slightly dry to moderate moisture areas such as woods, shady seeps, bluffs, woodland meadows along rivers, pastures, fence rows and disturbed sites like vacant lots.
White Snakeroot upper stems terminate in compound corymbs (flat-headed panicles of flowerheads) that span 2-6" across. Each flowerhead is made up of 10 or more white 5-parted disk florets (like "flowers within a flower"). Each floret is about 1/6 inch across and has protruding white styles.
White Snakeroot blooms July-October.
White Snakeroot is often confused with Common Boneset. However, White Snakeroot can easily be distinguished from Bonsets by its leaves. Among the species in this group, White Snakeroot has the broadest leaves; its lower leaves are cordate or broadly ovate, and these leaves have long petioles (a stalk that attaches a leaf). Common Boneset has pierced leaves (see Eupatorium perfoliatum drawing) and Tall Boneset has long slender leaves.
Above: (L) White Snakeroot leaves and (R) Common Boneset pierced leaves (leaves that surrounding the stem).
NOTE: White Snakeroot has caused fatalities from "Milk Sickness" because the White Snakeroot toxins can pass through the milk of dairy cattle to humans. It is reported that White Snakeroot is the plant that killed Abraham Lincoln's mother in 1818.
Above: White Snakeroot leaves along shore of Ho-Nee-Um Pond in Madison, Wisconsin. (8/22/19)
For more information on White Snakeroot, visit Wikipedia.
Or, for information on White Snakeroot (Ageratina altissima) visit the: Wisconsin State Herbarium.
Above: White Snakeroot in Oak Savanna in Madison, Wisconsin (7/21/20).
Above: White Snakeroot along shore of Ho-Nee-Um Pond in Madison, Wisconsin (9/12/20).
Above: White Snakeroot by Agawa Path in Madison, Wisconsin (9/13/20).
Above: White Snakeroot in Oak Savanna in Madison, Wisconsin (9/8/22).
Above: White Snakeroot specimen collected in Grant County near Platteville on September 9, 1987.
Above: 1913 White Snakeroot illustration.
Above: 1970 White Snakeroot illustration from USDA.
Above: For comparison reference, Common Boneset (Eupatorium perfoliatum) illustration by C.F. Millspaugh circa 1892.