Amaranthus retroflexus is a species of flowering plant in the Amaranthaceae family with several common names, including Red-root Amaranth, Redroot Pigweed, Red Rooted Pigweed, Common Amaranth, and common tumble weed.
True to its name, it forms a tumbleweed.It is native to the tropical Americas but it is widespread as an introduced species on most continents in a great number of habitats. This is an erect annual herb reaching a maximum height near 3 meters. The leaves are nearly 15 centimeters long on large individuals, the ones higher on the stem having a lance shape and those lower on the plant diamond or oval in shape. The plant is monoecious, with individuals bearing both male and female flowers. The inflorescence is a large, dense cluster of flowers interspersed with spiny green bracts. The fruit is a capsule less than 2 millimeters long with a "lid" which opens to reveal a tiny black seed.