Annual tufted herb 10 - 50 cm long
Leaves: having open sheaths that are inflated and hairless except for the small tufts of hairs (to 3 mm long) at the tips. The ligules are made of hairs 0.1 - 0.3 mm long, and the blades are 1 - 12 cm long, 0.6 - 2 mm wide, flat or with margins loosely rolling toward the upper surface of the midvein (involute), with smooth to minutely rough margins, hairless lower surfaces, minutely rough upper surfaces, and (occasionally) warty-based hairs near the base.
Inflorescence: terminal to axillary, branched (panicle), 2 - 5 cm long, 0.2 - 0.5 cm wide, cylindrical, with the base surrounded by the sheath. The primary branches are 0.4 - 1.8 cm long, appressed, and bear spikelets to the base.
Fruit: a transluscent light brownish to orangish-brown caryopsis, 1.2 - 1.8 mm long, inversely egg-shaped, flattened laterally, with fine longitudinal lines.
Culm: 10 - 45 cm long, erect to decumbent, thin but stiff, hairless.
Spikelets: 1.6 - 3 mm long, yellowish to cream, sometimes with a purple tinge, borne on an appressed stalk 0.1 - 2.5 mm long and minutely rough.
Glumes: nearly equal, lance-shaped to egg-shaped, membranous to thin but firm (chartaceous), hairless. The lower glume is 1.5 - 2.4 mm long, usually with a greenish midvein, and the upper glume is 1.7 - 2.7 mm long.
Florets: usually one per spikelet, with three purplish anthers 1.1 - 1.6 mm long.
Lemma: 1.6 - 2.9 mm long, egg-shaped with a pointed tip, thin but firm (chartaceous), hairless.
Palea: 1.6 - 3 mm long, egg-shaped, thin but firm (chartaceous), hairless, two-veined, often splitting between the veins when mature.
Similar species: Sporobolus vaginiflorus has sheaths that are sparsely hairy near the base, longer spikelets (2.3 - 6 mm), and lemmas with longitudinal lines. The other species of Sporobolus in the Chicago Region are perennials lacking inflated sheaths.
Flowering: September
Habitat and ecology: Compacted soils along road shoulders and railroad ballast.
Occurence in the Chicago region: native
Etymology: Sporobolus comes from the Greek words sporos, meaning seed, and ballein, meaning "to cast forth." Neglectus means overlooked.
Author: The Morton Arboretum
