Green foxtail Setaria viridis (L.) Beauv.
Life cycle: Annual
Native status: Introduced from China
Habitat: Crop fields, disturbed areas.
General description: Typically shorter than the other foxtails, but some biotypes can reach 3 to 4 ft in height. No hairs on the leaf blade, but margin of sheath has hairs. The tip of the seedhead bends slightly, whereas giant’s droops and yellow foxtail’s is erect.
Key ID traits: Hairy ligule. No hairs on upper leaf surface. The margin of the leaf sheath has hairs.
Similar species: The lack of hairs on leaf blade distinguishes green foxtail from the other foxtails. Fall panicum also has a hairy ligule and no hairs on leaf blade; however, the margin of fall panicum’s leaf sheath has no hairs, whereas green foxtail’s does. On larger plants, fall panicum has a prominent, light colored mid-vein on leaves and nodes on stems are swollen.
Miscellaneous: Several distinct biotypes of green foxtail are present in Iowa. They have been named robust purple foxtail, robust white foxtail, and giant green foxtail. At one time there was an effort to classify them as distinct species, but since they readily interbreed it was determined they should be considered biotypes, not species.