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: New Brunswick to Minnesota, southward to Georgia and Missouri. Habitat: Woodland borders, fields, and roadsides, fence rows, and thickets.
Stem one to four feet tall, erect, slender, round, and smooth. Leaves thin, finely rough, hairy, sharply toothed, heart-shaped to broadly ovate, long-pointed, the lower ones often five or six inches long and nearly as broad, with slender petioles; the upper ones much smaller, ovate to lance-shaped, short-petioled or sessile. Heads very numerous, in profuse panicled clusters at the ends of stem and branches, each about a half-inch broad, the rays light violet-blue; involucre top-shaped, its bracts appressed and tipped with short, obtuse, green points. Achenes very small, with whitish pappus.
Means of control the same as for New England Aster.