Redroot Pigweed: Amaranthus retroflexus
Weed Description: An erect summer annual that may reach 6 1/2 feet in height. Redroot pigweed is an abundant seed producer that may be found throughout the United States in horticultural, nursery, and agronomic crops, landscapes, roadsides, and also in pastures and forages.
Roots: A shallow taproot that is often, but not always, reddish in color.
Fruit: A single seeded utricle that reach 2 mm in length and are wrinkled when dry. Each utricle splits open in the middle to expose a single glossy black to dark brown seed that is 1 to 1.2 mm long and ovate in outline.
Identifying Characteristics: Dense, compact terminal panicles and relatively tall plants with alternately arranged leaves. Redroot pigweed is often confused with other similar pigweed species. For example, smooth pigweed is very similar, however this species has terminal panicles that appear less dense, compact, and bristly than those of redroot pigweed. Additionally, the bracts of smooth pigweed are only slightly longer than the sepals, unlike those of redroot pigweed. Palmer Amaranth (Amaranthus palmeri) also resembles redroot and smooth pigweed, however the terminal panicles of this species are much longer and narrower than the other pigweed species. These species may also resemble Common Lambsquarters (Chenopodium album) in the cotyledon stage, however common lambsquarter's cotyledons often have a mealy gray cast, and the first true leaves are alternate, unlike any of the pigweed species.