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: June to September.
Seed-time: August to November.
Range: New Brunswick to Minnesota, southward to Florida and Texas. Habitat: Fields, meadows, roadsides, and waste places.
Seeds of this plant are said to retain their vitality for several years, and they are too often an impurity of poorly cleaned clover and grass seed. Stem three to five feet in height, slender, four-sided, finely rough-hairy or sometimes smooth, with ascending branches. Leaves opposite, thin, oblong ovate, long-pointed, coarsely toothed, with short, grooved petioles; they are often splotched or covered with a white mildew fungus, which makes the weed most unsightly and a menace to better plants. Spikes loosely panicled, very long, slender, numerous, set very sparsely with tiny, white flowers, of which only a few are open at a time and these are hardly noticeable. Nutlets soon fall after ripening.
Small areas may be grubbed out or hand-pulled when the ground is soft; but land badly infested with this weed should be put under cultivation for a short rotation, in order that its perennial roots and dormant seeds may be cleaned from the soil.