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 October. Seed-time: September to November.
Range: Ontario to the Northwest Territory, southward to Virginia, Illinois, and Missouri. Habitat: Damp fields and meadows, borders of swamps.
Stem two to five feet tall, nearly smooth, slender, brownish, with many ascending, paniculate branches. Leaves narrow lance-shaped to linear, three to six inches in length, long-pointed, thin, smooth, sessile and entire or the lower ones toothed along the middle of each side and tapering to petioles. Heads in large, very numerous raceme-like panicles, smaller than related species or rather more than a half-inch broad, the many narrow rays white or very pale purple; involucre broadly top-shaped, its bracts closely imbricated, linear, acute, green-tipped. Achenes minutely hairy, with a white pappus.
Means of control the same as for the Purple-stemmed Aster.