This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Perennial. Propagates by seeds and by rootstocks.
Time of bloom: June to August.
Seed-time: July to October.
Range: Southern Maine to New Jersey, westward to Michigan.
Habitat: Roadsides, waste places.
Not a common weed in this country as yet, and should not be permitted to become so, for its creeping, horizontal rootstocks make it difficult to dislodge when once established; like the Cypress Spurge it grows in patches, smothering all weaker growths in its way.
Stems thickly clustered, ten inches to two feet tall, erect, slender, scaly at base, smooth above, branching near the top. Leaves narrowly oblong to lance-shape, a half-inch to nearly two inches in length, entire, sessile, whorled at the base of the umbel, few and scattering on the stalk. Umbel compound, its many rays fork-branched and bearing numerous opposite, greenish yellow bracts, broadly heart-shaped, with midvein extended in a minute bristle; involucres bell-shaped, nearly sessile, bearing four unappendaged, crescent-shaped brown glands. Capsule smooth, nodding on a long stipe; the seeds drab-gray, oblong, round and smooth, car-uncled at base.
Small areas, newly infested, should be grubbed out or destroyed with hot brine or caustic soda. Where too abundant to make such treatment practicable, close, persistent cutting, in order to starve the roots and prevent all seed development, will finally suppress the weed.