Seedling
The first leaf blade is linear and opens parallel to the ground. Leaves are rolled in the bud, lack auricles and have no ligule. Blades are 7-14 cm long and 3-5 mm wide, smooth on both surfaces, with rough margins. Sheaths are somewhat compressed/flattened, tinted maroon or purple toward the base and usually smooth. The collar is green and smooth.
Juvenile plant
In corn, barnyardgrass may be coarse, sprawling, and purple tinged; sometimes even prostrate and fan-shaped; or it may grow more upright like fall panicum.
Mature plant
Leaves are similar to those of seedlings, and ligules are absent. Blades are 10-20 cm long and 5-20 mm wide, lack hairs and are smooth to somewhat rough on both surfaces. The midvein is distinct and keeled near the base. Sheaths are open, compressed, and smooth, perhaps with a tuft of short hair at the base. The collar is whitish, broad, and smooth.
Root structure description
Roots are fibrous and shallow. Tillers often form adventitious roots where they touch the soil.
Flowers
Flowering occurs July-September. The seedhead is a coarsely branched green to purplish panicle. Spikelets are single-seeded, barbed along the nerves, and can have a long terminal awn.
Post senescene
Barnyardgrass plants are killed by the first hard frost, but the large thick stems and fan shape of the tillers remain well into winter.
