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 seed.
Time of bloom: June to September.
Seed-time: August to November.
Range: Virginia to Illinois and Missouri, southward to Florida and Texas. Habitat: Moist soil; wet meadows, sides of streams, and ditches.
The range of this poisonous weed has been greatly widened by the agencies of impure commercial seeds and baled hay; it is now locally abundant in New England and Pennsylvania and through the Middle West. The plant hybridizes with its sister autumnale, transmitting to the progeny its own earlier habit of bloom by which the weed is made more obnoxious.
Stem one to three feet tall, slender, angled, and narrowly winged by decurrent leaf bases, branching near the top, the younger foliage sparsely hairy. Leaves narrow lance-shaped to linear or the lower ones spatulate and toothed, the upper ones entire, sessile, and decurrent on the stem. Heads numerous, clustered at the ends of the many short branches, each about an inch and a half broad; disks bulging to nearly globular form, purplish brown, the florets perfect and fertile; rays pistillate but sterile, drooping, threetoothed at tips, yellow, often shading into brown at their bases, sometimes entirely brown, occasionally lacking, hence the name nudiflorum. Seeds oblong, hairy, the pappus of five or more awned scales. (Fig. 335.)
Means of control the same as for the autumn Sneezeweed.