Amaranthus retroflexus L.
Amaranthus retroflexus L. var. salicifolius I.M. Johnst.
Although other members of the Amaranthus genus are popular as food sources or landscaping plants, pigweed doesn’t get much respect. It is a common, gangly, rather unappealing weed. It is native to the tropical regions of the Americas, but has become more widespread.
Identification: Pigweed can reach 9' (2.7 m), but I usually see much smaller plants. Stems are often reddish near the base. Leaves are between 3-7" (7.6-17 cm) long. The flowers are green, about ¾" (1.9 cm) wide and 2-8" (5-20 cm) long.
Edibility: This is edible, and is eaten in some regions, but it may be high in oxalic acid or nitrates, so it should be boiled and the water discarded. Many other species of Amaranthus, such as pendent amaranth, serve as significant food sources.
Amaranthus retroflexus on the Virginia Tech Weed Identification Guide
Amaranthus retroflexus on the USDA Forest Service's Fire Effects Information Database
Amaranthus retroflexus at the Lady Bird Johnson Wildflower Center
Amaranthus retroflexus on Invasive.org, Center for Invasive Species and Ecosystem Health
Amaranthus retroflexus on Ontario Wildflowers
Amaranthus retroflexus on CalPhotos
Amaranthus retroflexus on Plants for a Future, a resource and information centre for edible and otherwise useful plants
Amaranthus retroflexus on the Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries
Amaranthus retroflexus at the University of Wisconsin's Robert W. Freckmann Herbarium
Amaranthus retroflexus on eFloras
Amaranthus retroflexus description by Thomas H. Kent, last updated 20 May 2018.