Dormancy

    Redroot Pigweed

    Amaranthus retroflexus

    redroot pigweed

    Redroot pigweed (Howard F. Schwartz, Colorado State University, Bugwood.org)

    redroot pigweed

    Redroot pigweed flowers (Joseph M. DiTomaso, Bugwood.org)

     

    Description

    • 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

    Location

    • 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.