Flowering plant, Lee County, Iowa
Redroot pigweed in cornfield, Jefferson County, Iowa
drawings of plant features
Seed leaves are long and narrow. First true leaves are strongly egg-shaped
with a deep notch at the tip. As seedlings mature the stem becomes very
Redroot pigweeds are tall plants with few branches. Stems tend to be green
or reddish in color with green leaves. Stems and leaves are very hairy.
Leaves are egg-shaped. Seedhead branches are few and tend to be short and
stout with a prickly appearance.
Bracts long, 4-7 mm. Tepals 5, longer than the fruit;
apices obtuse or retuse, sometimes reflexed. Stigmas 3.
Redroot pigweed is less difficult in general to manage than
common waterhemp. However, caution is needed. Some populations have
triazine resistant biotypes. Although not currently resistant to ALS
inhibiting herbicides, redroot pigweeds are known to hybridize with common
waterhemp in Iowa. Although most hybrid individuals are sterile, they can
produce some viable seed. These second generation hybrids have the
potential to backcross resistance genes into redroot pigweed populations.
An integrated program combining cultivation and appropriate herbicides
should facilitate effective redroot pigweed control.