A summer annual with thick stems that may reach 5 feet in height. One of the few grass weeds in which ligules are absent. Found throughout the United States, Canada, and Mexico as a weed of many agronomic crops, nurseries, landscape, and turf. Leaves are without hairs (glabrous), auricles, and ligules, and the leaf sheaths are often tinted red or maroon at the base. The stems are usually erect, thick, without hairs (glabrous), often branched at the lower nodes, and may be tinted red to maroon at the base.

Prior to seedhead formation, Fall Panicum (Panicum dichotomiflorum) and barnyardgrass are often confused due to their similar growth habit and appearance. However, the characteristic absent ligule of barnyardgrass helps to distinguish this weed from most other grasses in both the seedling and mature stage of growth.