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 Jersey to Illinois and Kansas, southward to Florida and Texas. Habitat: Rich soil; moist meadows and thickets.
Stems one to three feet tall, finely appressed-hairy, branching at the top. Leaves opposite, triangular ovate, truncate or heart-shaped at base, coarsely and bluntly toothed, with prominent veins and rather short petioles. Heads in rather compact corymbose clusters, each less than a quarter-inch across but very numerous, light blue or violet, the florets five-lobed and perfect. Achenes oblong, five-angled, the pappus a single funnel-formed row of tawny bristles.
Means of control the same as for Joe-Pye Weed.
 
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