This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Prenanthes racemose, Michx. (Nabalus racemosus, DC.)
Native. Perennial. Propagates by seeds.
Time of bloom: August to September.
Seed-time: September to October.
Range: New Brunswick to the Northwest Territory, southward to New York, New Jersey, Missouri, and Colorado. Habitat: Moist soil; prairies and banks of streams, wet meadows, and marshes.
A plant of very stately appearance, with a stout stalk, two to six feet or more in height, erect, simple, finely ridged, smooth, and glaucous, springing from a thick, tuberous, and very bitter root. Leaves light green, rather thick in texture, smooth, glaucous, the lower ones sometimes oval but usually oblong to obovate, four to eight inches in length, obtuse at apex, tapering to long, margined petioles, the edges with sparse and shallow teeth; upper ones much smaller, long-ovate to lance-shaped, acute, often entire, sessile, and partly clasping. Heads in a long, interrupted, spike-like panicle, the clusters densely crowded, some of the heads nodding but the greater number erect; florets pale purple, eight to fifteen in each head; involucre cylindric, with eight to ten linear bracts in its principal row, with a few short, spreading outer ones. Achenes small, slender, with fine, straw-colored pappus.
Fig. 382. - Smooth White Lettuce (Prenanthes racemosa).
Cut flower-stalks close to the ground before the buds unfold, thus preventing seed development and distribution. Drainage and cultivation of the soil are necessary in order to kill the perennial roots.