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 November.
Range: Throughout North America except the far North. Native of tropical America and indigenous in the Southwest. Habitat: Cultivated ground; waste places.
Fig. 73. - Russian Pigweed (Axyris ama-rantoides). X 1/4.
Like the Smooth Pigweed, this plant is rarely absent from cultivated ground. One reason for its constant recurrence lies in the long vitality of its seeds, which are known to survive in the soil for more than thirty years; they are also a frequent impurity of all commercial seeds.
Stem stout, tough, erect, green, rough-hairy, much branched, occasionally attaining a height of ten feet, but usually one to six feet tall, springing from a long, fleshy, red taproot, befringed with pink or white rootlets. Leaves long ovate or rhombic-ovate, three to six inches in length, dull green, rough-hairy, with long petioles and prominent ribs and veins. Flowers on large, dense, terminal and axillary panicles, each subtended by three rigid, prickly bracts; they are very small, greenish, with five sepals and five stamens; stigmas two or three. Each flower produces but one oval, flattened, jet-black, and shining seed which readily falls from its place when ripe. (Fig. 74.)
Prevent seed production. This means that attention must be given to cultivated crops after the horse-hoe has ceased its rounds, either hand-pulling or hoe-cutting late plants which persistently strive to reproduce themselves. If they are nearing maturity, remove the plants from the ground, for seeds will ripen on the stout stalks. In grain fields, seedlings may be dragged out with a weeding harrow in the spring, when the crop is but a few inches tall. Or later, but before the weed blooms or the grain begins to head, spray with Iron or Copper sulfate.
Fig. 74. - Rough Pigweed (Amaranthus retroflexus). X 1/4.