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: August to November. Range: Throughout the world. Habitat: Cultivated fields, gardens, waste places.
A succulent, swift-growing weed, which rapidly absorbs the food and moisture needed by the crops among which it intrudes. Pigs and sheep are very fond of it, and when young it makes quite as good "greens" as its cultivated relatives, the spinach and the beet; also, it is a frequent host of the insect enemies, mildews, and rusts that injure those plants. (Fig. 69.)
The stem sometimes attains to six feet, but is usually two to four feet tall, stout, erect, ridged and grooved, much branched, often striped with pink or purple, growing from a short, stout main root with many branching rootlets. Leaves rhombic-ovate or goosefoot-shaped near the base, but become more narrow and lance-shaped as they ascend the stem until those near the top are often nearly linear; smooth and green above but often covered on the under side with a mealy secretion, especially when young, the lower ones irregularly cut and toothed, with petioles often as long as the blades. Flowers small, green, crowded on spiked panicles in the axils and at the summit of stem and branches; calyx with five lobes, keeled and enfolding the seed, which is lens-shaped, small and black; these seeds have very long vitality, lying dormant in the soil for years and germinating when brought near the surface by cultivation. Pigweed seeds are nearly always found in dirty grain, and often in clover and grass seed and in alfalfa; though, being lighter, they should be easily removed.
In hoed crops the weed is very persistent and cultivation should be continued until late in the season, else the soil will be strewn with late matured seeds. In gardens and other small areas, it should be hoe-cut or hand-pulled while young. When the plant appears in grain fields, it should be harrowed out with one of the small-toothed harrows known as weeders, in the spring, when the grain is but a few inches high. Stubbles should be given surface cultivation after harvest for the purpose of stirring into life such seeds as lie on the ground, the young growth to be turned under at the fall plowing, or, it may be grazed off by sheep.
Fig. 69. - Smooth Pigweed (Chenopodium album). X 1/4.