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: June to September. Seed-time: Late July to November.
Range: Massachusetts to Michigan, Illinois, and Kansas, southward to the Gulf of Mexico. Habitat: Cultivated ground, meadows, lawns, and waste places.
A native of tropical America and a very common and troublesome weed, particularly in the Southern States. Not known north of Mason and Dixon's Line until after the Civil War, when it suddenly appeared in many places - most probably transported in the feed-bags of returning cavalrymen, which is the reason why it is called Soldier Weed, not because of its own weapons. Stem one to four feet tall, stout, grooved, erect, smooth, branching and bushy, dark green or often purplish red. Leaves one to three inches long, broadly lance-shaped, pointed at both ends, the lower ones with long petioles; at the base of each leaf is a pair of diverging stipular spines, one-fourth to one-half inch long, rigid, keen as awls. Flowers small, greenish, the upper ones mostly staminate, forming long, slender spikes; fertile ones below in the axils, the clusters usually nearly globular; bracts awl-like, about as long as the scarious, sharp-pointed sepals; stamens five. Seed very small, lens-shaped, smooth, dark, shining brown, imperfectly covered by the utricle; it is too often an impurity of other seeds, and, like all its family, is possessed of long vitality in the soil. (Fig. 77.)
Fig. 77. -Spiny Amaranth (Amaranthus spinosus). X 1/4.
Prevent seed production. In meadows or permanent pastures every stalk should be closely cut or hand-pulled before the flower-spikes develop. Cultivated ground should not be neglected in the latter part of the season, for it is the late-blooming plants that usually seed the soil. Potato and corn land should be plowed or well disked after harvest, and a winter crop sown which will keep down the weed.