This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual or biennial. Propagates by seeds.
Time of bloom: July to September.
Seed-time: August to October.
Range: Locally distributed in Nova Scotia and Ontario and near the seaports of the Atlantic States; has reached as far inland as Ohio.
Habitat: Fields, roadsides, and waste places.
The achenes of this plant have been reported as an impurity in alfalfa seeds; it is a very unpleasant weed, rejected by grazing animals because of its bitter juices and prickly-hairy foliage, and it should, if possible, be hindered from extending its range.
Stems fifteen to thirty inches tall, branched, and closely set with stiff, prickly bristles. Lower and basal leaves large, spatulate, irregularly toothed, narrowed to margined petioles; stem-leaves much smaller, usually entire, sessile and clasping. Heads yellow, in spreading corymbose panicles, on short peduncles, each about a half-inch broad, the outer bracts of the involucre very large and leaf-like, prickly-hairy, the inner ones membranous, narrow and pointed. Achenes reddish brown, long-beaked like those of the Dandelion, with a very plumose pappus to help in their distribution. (Fig. 367.)
Fig. 367.- Bristly Oxtongue (Picris echoides).
Deep cutting with hoe or spud while in first flower, making certain that no seed is allowed to mature.