Integrated Pest Management

Redroot Pigweed

Amaranthus retroflexus

redroot pigweed

Redroot pigweed (Howard F. Schwartz, Colorado State University,

redroot pigweed

Redroot pigweed flowers (Joseph M. DiTomaso,



  • upright plant 1 – 6 feet tall with thick stems and a taproot
  • lower stems are often reddish or red striped
  • leaves are oval with a tapering point, occasionally tinted red
  • densely clustered flowers appear on a spike at the tip of branches
  • flowers are green with a pinkish tint


  • gardens, cropland and open spaces

Life Cycle

  • summer annual; germinates primarily in summer, and anytime when soil moisture is sufficient
  • plants produce tens of thousands of seeds that stay viable up to 10 years or more

IPM Recommendations

  • Seed populations can be reduced by soil solarization.
  • Competition for light from taller desired vegetation can help control weedy patches.
  • Apply a mulch layer 3 inches deep on planting beds to reduce seed germination.
  • Pre-emergent herbicides are not always effective since germination can take place year-round.
  • Apply an appropriate post-emergent herbicide directly to target weeds.