This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Native. Perennial. Propagates by seeds. Time of bloom: August to September. Seed-time: September to November.
Range: New Brunswick to Manitoba, southward to Florida and Texas. Habitat: Damp meadows, moist woods and thickets, sides of streams and ditches.
Joe Pye was an Indian "herb doctor" of early days in New England, who is said to have performed many marvelous cures, mostly with decoctions of this herb. However that may be, its woody, fibrous, blackish roots, gathered in autumn and carefully dried, are still salable in the drug market for two to four cents a pound.
Stem round, smooth or sometimes finely grooved, slender for its height of three to ten feet, usually purple, simple or with a few branches at the top. Leaves arranged in whorls of three to six, long-ovate, thin, smooth except for a slight hairiness of the veins beneath, finely scallop-toothed, tapering to short, slim petioles. Heads small, in rather long, round-topped, corymbose clusters, pinkish purple, fragrant; the florets all tubular and perfect. Achenes very small, black, angled, with a funnel-shaped pappus of fine, bristly hairs. The plant is often accompanied by a nearly related variety, the Spotted Joe-pye Weed (E. maculatum, L.), differing in that it has rough-hairy leaves and stem, green and more or less spotted with purple; heads similar, but with broader, flatter cluster and the root also is medicinally valuable. (Fig. 291.)
Fig. 291. - Joe-Pye Weed (Eupatorium purpureum).
Only grubbing out bodily or repeated deep cutting throughout the growing season will rid grasslands of this weed. Plants on waste grounds and in thickets should also be prevented from seed production.