Plants perennial; cespitose, occasionally rhizomatous. Culms 40-130(150)
cm tall, 1-4 mm thick, frequently glaucous. Sheaths with sparsely hairy
apices, hairs to 3 mm , not conspicuously tufted; uppermost sheaths 0.5-3
mm wide; ligules 0.1-0.4 mm; blades 4-23 cm long, 1.5-4 mm wide,
flat or involute, abaxial surface glabrous or pilose, adaxial surface glabrous
or scabridulous, margins glabrous. Panicles terminal and axillary, 5-11
cm long, 0.04-0.2(0.3) cm wide, with 10-40 spikelets per cm2, narrow,
sometimes spikelike, included in the uppermost sheath; lower nodes with
1-2(3) branches; primary branches 0.4-5 cm, appressed, spikelet-bearing
to the base; secondary branches appressed; pulvini glabrous; pedicels
0.3-3.5 mm, appressed, glabrous or scabridulous. Spikelets 4-9(10) mm,
stramineous to purplish-tinged. Glumes subequal, lanceolate, membranous
to chartaceous, midveins usually greenish; lower glumes 1.5-6.2 mm; upper
glumes (2)2.5-5(6.5) mm, slightly shorter or longer than the lemmas; lemmas
(2.2)3-7(7.4) mm, lanceolate, chartaceous and opaque, minutely appressed pubescent
or scabridulous, occasionally 2- or 3-veined, acute to obtuse; paleas (2.2)3-9(10)
mm, ovate to lanceolate, chartaceous; anthers 2.2-3.2 mm, yellow to orangish.
Fruits (1.5)2.4-3.5 mm, ellipsoid, laterally flattened, often striate,
reddish-brown; pericarps loose, but neither gelatinous nor slipping from
the seeds when wet. 2n = unknown.
Sporobolus clandestinus grows primarily in sandy soils along the coast
and, inland, along roadsides. In the southeastern United States, it is found in
dry to mesic longleaf pine-oak-grass communities and cedar glades. Its range lies
entirely within the Flora region.
Perennial tufted herb, sometimes forming rhizomes 40 cm - 1.6 m tall Leaves: with open sheaths to 3 mm wide and ending in sparsely hairy (to 3 mm long) tips. The ligules are made of hairs 0.1 - 0.4 mm long, and the blades are 4 - 23 cm long, 1.5 - 4 mm wide, flat or with margins rolling toward the upper surface of the midvein (involute), hairless or soft-haired beneath, and hairless or minutely rough above. Inflorescence: terminal and axillary, branched (panicle) and sometimes spike-like, 5 - 11 cm long, 0.4 - 3 mm wide, the base surrounded by the sheath. The appressed primary branches are 0.4 - 5 cm long and bear spikelets to the base, and the swelling in the branch axils (pulvinus) is hairless. Fruit: a reddish brown caryopsis, 1.5 - 3.5 mm long, elliptic, flattened laterally, usually longitudinally lined. The matured ovary wall (pericarp) is loose but does not become gelatinous or separate from the seeds when wet. Culm: 40 cm - 1.5 m long, 1 - 4 mm across, hairless, often covered with a whitish waxy coating (glaucous). Spikelets: ten to 40 per square cm, tan to purple-tinged, 4 - 10 mm long, borne on an appressed and hairless or minutely rough stalk 0.3 - 3.5 mm long. Glumes: nearly equal, lance-shaped, membranous to thin but firm (chartaceous), usually having greenish midveins. The lower glume is 1.5 - 6.2 mm long, and the upper glume is 2 - 6.5 mm long. Florets: usually one per spikelet, with yellow to orangish anthers 2.2 - 3.2 mm long. Lemma: 2.2 - 7.4 mm long, lance-shaped with a pointed to blunt tip, sometimes two- to three-veined, opaque, thin but firm (chartaceous), minutely rough or minutely appressed-hairy. Palea: 2.2 - 10 mm long, egg-shaped to lance-shaped, hairless, thin but firm (chartaceous), two-veined, often splitting between the veins when mature.
Similar species: Sporobolus neglectus and Sporobolus vaginiflorus are annuals that are easily distinguished by their inflated sheaths. The spikelets of Sporobolus cryptandrus are less than 3 mm long. Sporobolus compositus var. compositus has transparent, hairless lemmas and 1 - 1.8 mm long caryopses, while Sporobolus heterolepis has open, fragrant inflorescences extending above the uppermost leaf sheaths.
Habitat and ecology: Local in sandy prairies.
Occurence in the Chicago region: native
Etymology: Sporobolus comes from the Greek words sporos, meaning seed, and ballein, meaning "to cast forth." Clandestinus means concealed.
Much like no. 7 [Sporobolus asper (P. Beauv.) Kunth]; perennial, occasionally rhizomatous, with solitary or tufted culms 4-17 dm; lower sheaths frequently pubescent, the collar usually pubescent but only rarely pilose; lvs often hairy, lemma (2.5-)3-7 mm, pubescent; palea pubescent, equaling to sometimes much surpassing the lemma; pericarp becoming loose when wet, but not gelatinous; 2n=46, 48, 52, 54, 56. Dry sandy soil and prairies; Tex. to Fla., n. to Kans., Io., s. Wis., Ind., Va., and near the coast to Mass. (S. asper var. c.; S. canovirens)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.