Family Compositae or Asteraceae (Composite family). This is one of the Thoroughwort group in the Composite family, all of which were previously placed in the genus Eupatorium, but have now been distributed among several genera.
One of our most decorative late-summer and autumn
flowers, White Snakeroot lights up the edge of the
woods and can form a perfect ornamental border around
a field. Its beauty comes at a price: it’s poisonous
to cattle, and the poison can be transmitted through
their milk. “Milk sickness” killed Abraham Lincoln’s
mother. But if you don’t have cattle, and you don’t
eat the plant yourself, there’s no reason not to enjoy
this beautiful wild native. The plants above grew at
the edge of the woods in Beechview, where they were
blooming in late September.
As a member of the Composite family, this species is
especially interesting for the way the individual
little five-parted flowers are easily distinguishable
in the heads. It’s a good plant for demonstrating the
construction of a Composite flower to children.
Flowers: Heads discoid (that is, with no ray flowers), in irregular flattish corymbs; flowers pure white, with protruding stamens, also white.
Leaves. Opposite; oval, pointed, toothed, finely rough; underside with many prominent ribs; lower leaves flattish at base or almost cordate; on petioles about 1/3 the length of the leaves.
Stem: Smooth, flexible; much branched from leaf axils; averaging about 4 feet, but quite variable and can be much taller.
Gray lists this plant as Eupatorium urticaefolium:
EUPATÒRIUM [Tourn.] L. THOROUGHWORT. Heads discoid, 3-many-flowered; flowers perfect. Involucre cylindrical or bell-shaped, of more than 4 bracts. Receptacle flat or conical, naked. Corolla 6-toothed. Achenes 6-angled ; pappus a single row of slender capillary barely roughish bristles. — Erect perennial herbs, often sprinkled with hitter resinous dots, with generally corymbose heads of white, bluish, or purple blossoms, appearing near the close of summer. (Dedicated to Eupator Mithridates, who is said to have used a species of the genus in medicine.)
1. EUPATORIUM proper. Receptacle flat.
Heads 5-30-flowered; involucral brada nearly equal, in one row or but a very few of the outermost shorter; leaves opposite, ovate, petioled, triple-nerved, not resinous-dotted.
Leaves broadly ovate; flowers pure white.
E. urticaefólium Reichard. (WHITE SNAKEROOT.) Smooth, branching, 0.5-1 m high; leaves broadly ovate, pointed, coarsely and sharply toothed, long-petioled, thin, 7-12 cm. long; corymbs compound. (E. ageratoides L. f.) — Rich woods, not rare. Var. villicaúle Fernald. Stems and petioles viscid-villous. — Pa. (Heller) to Va. (Curtías).