Flowering plant, Lee County, Iowa
(Amaranthus hybridus, AMACH)
drawings of plant features
Seed leaves are long and narrow. First true leaves are strongly egg-shaped
with a deep notch at the tip. Seedlings become hairy as they mature.
Smooth pigweeds are tall plants with few branches. Stems and leaves tend
to be red or green. Leaves are egg-shaped. Stem and leaves tend to be
slightly hairy, but not roughly hairy like redroot pigweed. Seedhead
branches are numerous, long, thick, and slightly prickly.
Bracts short, 3-5 mm long. Tepals 5, shorter than the
fruit; apices acute to acuminate; straight. Stigmas 3.
Smooth pigweed is less common than redroot pigweed in Iowa,
and appears to be restricted to the southeastern corner of the state.
Because it is extremely weedy in Illinois and Missouri, the potential for
spread into Iowa from these states is great. Management of smooth pigweed
is similar to that of redroot pigweed. Smooth pigweed biotypes outside of
Iowa have been found with multiple resistances to ALS and triazine