Redroot Pigweed

Weeds

red root, rough pigweed, Chinamens greens

Amaranthus retroflexus


Redroot pigweed is a summer annual broadleaf weed that is typically associated with new establishments and other areas of disturbed soil (compost piles, gardens). Redroot pigweed is a prolific seeder and is associated with late summer allergies. The leaves of redroot pigweed are ovate (wider in the middle), shiny and very thin. The veins on the leaves are very prominent. Flowers form at the terminal and in axillary spikes. Pigweed will not usually persist in a mowed turf. However, it can establish in cool-season lawns during July and August when mowing frequency is reduced due to high temperatures and minimal soil moisture. Increased turf density and a little patience is the best remedy for redroot pigweed.

  • Crops Affected: Turfgrass

    Management

    Redroot pigweed is a small-seeded summer annual weed that needs soil disruption to expose the seed and encourage germination. Redroot pigweed is most common in new establishments where the turfgrass is not very dense or competitive. Patience is the best cure for redroot pigweed as it will not persist once routine mowing is applied. Redroot pigweed re-establishes by seed each season. For this reason, it is unlikely that redroot pigweed will invade a thick vigorous turf in the year after establishment. This is a case where improved turfgrass vigor and density is extremely effective at limiting future populations.

    Similar Species

    There are a few pigweeds common to Michigan. Smooth Pigweed, Powell Amaranth, and Redroot Pigweed are somewhat difficult to distinguish until they produce seed. Powell amaranth is most often confused with redroot pigweed. The management recommendations for these species is the same (improve turfgrass vigor and density). If flowering, Powell amaranth produces a much more slender spike than redroot pigweed. Prostrate pigweed is a mat-forming cousin of redroot pigweed that has entire margins and is typically wider at the apex. Common lambsquarters also invades new seedings but serrated, thicker leaves with less-prominent veins.