Amaranthus, which are short-lived herbs of the amaranthaceae family, generally are native to tropical and mild climates in almost all parts of the world. The genus of Amaranthus contains more than 50 species, including pigweed, tassel flower, and Joseph's coat. Although Amaranthus is primarily an ornamental plant, the Incas and Aztecs used the amaranth plant as a food, and in many regions people still do so.
Many species provide food as leaf vegetables, cereals, and flours, and most are highly nutritious. In many countries, people eat the leaves as greens, use the plant as an herb for flavoring, and eat the grains. Depending on the cultivar, the seeds may contain up to 20 percent protein, making them valuable for vegetarians. Many American health food stores carry amaranth flour and cereal. A popular treat called alegra is toasted amaranth grains mixed with honey or molasses.
The flowers are small and have perianth and bracts instead of petals, which range in color from white or greenish white to brownish red or red in color, varying by the cultivar. Most species have spikes or heads of long-lasting blooms. Depending on the species and cultivar, the flower groups may be upright or drooping panicles, which are loose branching pyramid-shaped flower clusters. The leaves often are colorfully mottled. Joseph's Coat, A. tricolor, usually has green, yellow, and scarlet splotched leaves that are three to six inches (about eight to 15 cm) long and two to four inches (about five to 10 cm) wide.
Often gardeners use Amaranthus in landscaping or container plantings. Most find that poor soil gives more colorful foliage. Some of the species that gardeners usually plant are the love-lies-bleeding or tassel flower, fire amaranthus, and fountain plant. A. hybridus is a common weed in most places, but a cultivar of it called hypochondriacus, or prince's feather, often is a fine garden specimen. Other plants in the Amaranthus family are weeds, notably pigweed and tumbleweed.
At least nine of the pigweed species have multiplied aggressively since the 1990s. Experts believe the rapid spread of these species is at least in part owing to new farming techniques, including reduced or no tillage, less herbicidal use, and herbicidal-resistance species. A new strain of the Palmer amaranth, Amaranthus palmeri, often is glyphosate resistant, and the most common herbicides do not kill it. Cotton and soybean growers generally are most at risk, although all farmers in temperate regions typically need to battle this weed. In field tests, soybean yields were reduced 17 to 68 percent because of the palmer amaranth infestation.