Ageratina altissima (L.) R.M. King & H. Rob.

White snakeroot, tall boneset, white sanicle

Some similar species

	Eupatorium capillifolium	Eupatorium perfoliatum	You are here Ageratina altissima
Common Name	dogfennel	boneset	white snakeroot
Plant	1½–6½′ (50–200 cm) tall, erect, with several forked stems. Stems are round, light green or reddish to dark red or purple, and finely hairy. Stems are soft when young, becoming woody and tough later.	Plants reach 3′ (1 m) high. The stout, very hairy stem branches at the top to support the flowers.	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	Leaves are finely divided and needle-like. When crushed, they produce an unpleasant odor.	Opposite leaf pairs are joined around the stem, so that the stem appears to be growing through them. Leaves are up to 8″ (20 cm) long, long and narrow, with pointed ends and fine serrations. Prominent veins produce a rough upper surface and a hairy, somewhat sticky lower surface.	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 ⨉ 1–3″ (6.3–15 ⨉ 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	A profusion of tiny, inconspicuous greenish-white flowers 1/16–⅛″ (2–3 mm) long appear all over the upper segments of the plant. Flowers appear from June to November.	Small, dull white (sometimes pinkish) flowers are flat-topped or slightly dome-shaped clusters. Individual flowers are about ⅛″ (3 mm) in diameter. The flowers lack petals ("rays") and look like tiny shaving brushes.	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.
Fruit	Small achenes ~1/32″ (1–1.5 mm) long.	Achenes have small tufts of hair for wind dispersal.	Tiny black bristled 5-angled achenes equipped with equally tiny parachutes.
Range/ Zones	USDA Zones: 3-10	USDA Zones: 3-8	USDA Zones: 4-8
Habitats	On roadsides, in flatwoods, marshes, and disturbed areas.	Wet soils in low woods, thickets, stream banks, meadows and prairies.	Woods, brush thickets, and shady areas with open bare ground.

	Ageratina altissima ‘Chocolate’
Common Name	white snakeroot
Plant	Plants are 3–5′ (91–152 cm) high, and up to 3′ (91 cm) around, with single or multiple stems.
Leaves	Leaves are 2–5″ (5–12 cm) long, lance-shaped, and tapering at both ends; lower leaves are broader, more heart-shaped. Each leaf has three prominent veins and serrated edges. Leaf stems (petioles) are ½–1½″ (1.3–3.8 cm) long. Leaves are darker in the 'Chocolate' cultivar.
Flowers	Flowerheads are somewhat dome-shaped clusters, each with 10-30 white brushlike flowers with no petals. Each flower is about ⅛″ (4 mm) around.
Fruit	Tiny black bristled 5-angled achenes equipped with equally tiny parachutes.
Range/ Zones	USDA Zones: 4a-8b

Ageratina altissima description by Thomas H. Kent, not updated.

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