Ageratina altissima (L.) R.M. King & H. Rob.
White snakeroot, tall boneset, white sanicle
White snakeroot is native to eastern North America.
Plants: Up to 5' (1.5 m) high, growing as a single plant or a clump with multiple stems. Stems are light green, sometimes tan, round, with few or no hairs.
Leaves: Near the base of the plant, leaves are are heart-shaped to oval (cordate to cordate-ovate). Leaves further up the stem are narrower and more lance-shaped (lanceolate). The leaves are 2½-6" (6.3-15 cm) × 1-3" (2.5-7.6 cm), with sharp, coarse serrations. Leaf undersides have prominent veins. Leaf stems are longer than most, from ½-2½" (1.3-6.3 cm) long.
Flowers: White snakeroot blooms in rounded corymbs, each containing 10 to 25 white flowers about ⅛" (5 mm) around. Each flower is a composite flower, composed of a central disc and surrounding petals. Since each petal is technically a flower in its own right, you could say that white snakeroot contains flowers within flowers within flowers. Or petals and disc flowers within flowerets within inflorescences. Or just white fuzzy-looking flowers.
Fruits: Tiny black bristled 5-angled achenes equipped with equally tiny parachutes.
Edibility: Poisonous Plants contain tremetol and glycosides, which together cause staggers, a potentially fatal disease in cows. These plants are also toxic to people, and milk from cows exposed to white snakeroot can also cause illness called “milk sickness” in people. In the 1800s, when drought sometimes forced cows to forage in forests for food, this caused extensive deaths.
Ageratina altissima at Illinois Wildflowers
Ageratina altissima at the Northeast School of Botanical Medicine (describes this and similar species)
Ageratina altissima on Kansas Wildflowers and Grasses
Ageratina altissima on Southeastern Flora, the Southeastern U.S. Plant Identification Resource
Ageratina altissima at Minnesota Wildflowers
Ageratina altissima at the Vanderbilt University Bioimages web site
Ageratina altissima on the Connecticut Botanical Society's Connecticut wildflowers site
Ageratina altissima on Plants for a Future, a resource and information centre for edible and otherwise useful plants
Ageratina altissima on www.pinecreekvalley.com
Ageratina altissima on Discover Life
Ageratina altissima description by Thomas H. Kent, last updated 1 Sep 2021.
Range: Zones 4-8: