Pigweed, red root, careless weed, green amaranth, Chinamanís greens
Characteristics. This native to tropical Latin America is now widespread in the United States and commonly found in cultivated crops, landscaping and wastelands. A related species, Powell araranth, is readily distinguished from redroot pigweed by the presence of longer, narrower and spiny appearing flower bracts in the former. This weed will germinate all year long with sufficient soil moisture, but first frost will annihilate all redroot pigweed. So control measures are not necessary to kill this weed late in the year. Pigweeds contain nitrates that can be toxic to livestock when consumed.
Identifying Characteristics. This coarse erect annual typically grows to 2 to 4 feet tall; however, growth is variable depending largely on its environment. In the open, with no competing vegetation, pigweed will grow erect and at the same time develop branches that grow laterally and then up. Pigweed can grow and reproduce very close to the ground if mowing or similar disturbances prevent it from growing upright. Generally, pigweed grows upright in large masses or clumps. Pigweed (Amaranthus retroflexus) foliage is simple, often with a wavy margin, ovate in shape, and dull green. Venation in the leaves is distinct.
Redroot pigweed flowers are green and form terminal and axillary panicle-like spikes. When under stress, or constantly mowed to a low height, pigweed can flower at a very small size.† As the name indicates the upper root areas of this plant are typically red in coloration.
Seedlings have linear cotyledons and leaves with distinct veins and long stems.