This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual. Propagates by seeds.
Time of bloom: July to September.
Seed-time: August to October.
Range: Throughout North America except the far North.
Habitat: All soils; invades all crops.
Fig. 10. - Green Foxtail (Setaria viridis). X 1/4.
Culms one to three feet tall, erect, usually simple but sometimes branched, growing in tufts. Sheaths smooth; blades three to ten inches long, one-fourth to one-half inch wide, rough on the margins, dark green. Spikes two to four inches in length, rather thick, the involucral bristles subtending the spikelets being nearly a half-inch long, two to six for each flower, green or sometimes yellowish, barbed upward. Seed similar to that of Yellow Foxtail but slightly smaller, very common in clover seed. Also it seems a worse pest in lawns and gardens than either of its relatives. (Fig. 10.)
Hoe-cutting or hand-pulling while the tufts are small, in lawns and gardens; surface cultivation or burning over of stubbles after harvest; prevention of seeding in all ways possible.