Modified (16 Jun 2009) to reflect the discovery of O. burmannii in Florida and (10 Oct 2010) recognition of O. undulatifolius as a species rather than a subspecies. M. Barkworth

Plants annual or perennial. Culms 10-100 cm, weak, trailing on the ground, branching. Leaves cauline; ligules membranous and ciliate, or of hairs; blades lanceolate. Inflorescences terminal, panicles of unilateral branches, spikelets paired (but the first spikelet sometimes reduced), rachises and branches terminating in a spikelet; branches 0.1-7 cm, persistent; disarticulation below the glumes. Spikelets dorsally compressed, not sunken into the rachis, lacking subtending bristles, with 2 florets. Lower glumes awned; upper glumes not ciliate on the margins, unawned or with awns shorter than those of the lower glumes, awns of both glumes often becoming viscid; lower florets sterile or staminate; lower lemmas acute to shortly awned; lower paleas present or absent; upper florets bisexual; upper lemmas papery to leathery, glabrous, smooth, unawned, white or yellow at maturity; upper paleas similar to the upper lemmas. x = 9. Name from the Greek hoplismenos, armed, alluding to the awned spikelets.

This treatment is based on Scholz (1981; English translation), according to which Oplismenus is a genus of five closely-related species that grow in shady, mesic forests of tropical and subtropical regions. Her work was based almost entirely on examination of herbarium specimens. The modifications made here reflect recent work. In the Flora region, it is represented by two native taxa and two recently introduced weedy taxa. The aggressive nature of one of the introduced taxa, O. undulatifolius, was not recognized until relatively recently.

The awns of some species of Oplismenus become viscid at maturity, aiding in fruit dispersal (Scholz 1981; Davidse 1987).

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SELECTED REFERENCES Chen, SL. and S.M. Phillips. 2006. Oplismenus. Pp. 501-504 in ZY. Wu, P.H. Raven and DY Hong (eds).Poaceae, Flora of China vol. 22. Science Press and Missouri Botanical Garden Press; Davey, J.C. and W.D. Clayton. 1977. Some multiple discriminant function studies on Oplismenus. Kew Bull. 33:147-157; Davidse, G. 1987. Fruit dispersal in Poaceae. Pp. 143-155 in T.R. Soderstrom, K.W. Hilu, C.S. Campbell, and M.E. Barkworth (eds.). Grass Systematics and Evolution. Smithsonian Institution Press, Washington, D.C., U.S.A. 473 pp.; Davis, S. B., W. S. Judd, and K. D. Perkins. 2006. Noteworthy collection in Florida. Castanea 71: 333–334; McVaugh, R. 1983. Flora Novo-Galiciana. A descriptive account of the vascular plants of western Mexico. Gramineae 14:1–436. University of Michigan Press, Ann Arbor, Michigan; Peterson, P.M., E.E. Terrell, E.C. Uebel, C.A. Davis, H. Scholz, and R.J. Soreng. 1999. Oplismenus hirtellus subspecies undulatifolius, a new record for North America. Castanea 64:201-202; Scholz, U. 1981. Monographie der Gattung Oplismenus (Gramineae). Phanerog. Monogr. Tomus XIII. J. Cramer, Vaduz, Germany. 217 pp. English translation being posted.

Oplismenus burmannii (Retz.) P. Beauv.
Burmann's Basketgrass

Plants annual, usually slender. Culms (15)25-45(65) cm tall; nodes hairy; internodes grooved, usually hairy in the grooves, less so than over the nodes. Leaves light green; sheaths glabrous or sparsely hairy, the edges ciliate; ligules 0.6-1.2(1.8) mm, ciliate; blades (2)3-7(8) cm long, 6-13 (16) mm wide, ovate-oblong to oblong-lanceolate, usually hairy , midvein weak, with 2-3 lateral veins on each side, cross venation usually visible. Panicles (3)4-8(10) cm, sometimes hairy, with 3-10 primary branches; lower primary branches (0.2)0.5-1.5(3) cm long, with (3)10-20(25) spikelets, spikelets borne in pairs, usually encircled at the base with hairs almost as long as the spikelets. Spikelets (2)2.8-3.5 mm long, usually densely hairy, sometimes glabrous, flattened to rounded on the back. Lower glumes (1.3)1.9-2.4 mm, 0.7-0.9(1.2) mm wide, oblong-oval, densely hairy, with 3-5(7) veins, awned, awns (3)6-11(15) mm long, frail, whitish, and scabrous; upper glumes (1.5)2-2.3 mm long, (0.7)-1.2(1.5) mm wide, similar to the lower glumes in shape, fairly densely hairy, with 5-7 veins, awned, awns (0.4)3-6(9) mm long, frail, whitish, and scabrous; lower lemmas (2)-2.6-3.5 mm long, (1)1.7-2.4 m wide, oblong, with (5)7-9(11) veins, pointed or shortly awned; lower paleas absent. Caryopsis oblong-lanceolate.

Oplismenus burmannii is a pan-tropical species that is most abundant in Africa. It was discovered in Florida in 2006 (Davis et al. 2006). It was treated by Scholz (1981) as O. hirtellus subsp. affinis. Davis et al. (2006) cite McVaugh (1983) in support of its recognition as a species.

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Oplismenus hirtellus (L.) P. Beauv.
Bristle Basketgrass

Plants perennial. Culms to 90 cm, mostly decumbent and rooting at the nodes, distal 15-35 cm ascending when flowering; nodes usually pubescent; internodes usually pubescent along 1 side (sometimes glabrous). Sheaths conspicuously ciliate on the margins; ligules 0.4-1.6(2.3) mm, ciliate; blades (0.6)1.3-11.5 cm long, 2-20 mm wide, glabrous, scabrous, or pubescent, margin(s) usually undulating. Panicles (1.5)2.5-16.5 cm, with 2-10 primary branches; branches 0.1-2.5 cm. Spikelets 2.2-3.5(4.5) mm; calluses shortly pubescent at the base awns usually purplish. Lower glumes 1.5-3 mm, scabridulous and/or pubescent, 3-5-veined, awns (1.6)3.2-14.5 mm; upper glumes 1.5-2.5 mm, sparsely pubescent, 5-7-veined, awns 0.8-6(10) mm; lower florets usually sterile, occasionally staminate; lower lemmas 2.2-3.1 mm, sparsely pubescent above, (5)7-9-veined, awns 0.1-1.2 mm; lower paleas absent or to 2.3 mm, hyaline; upper lemmas (2.1)2.3-3 mm, glabrous, weakly cartilaginous, white to cream-colored; anthers 3, 1.3-1.7 mm. Caryopses 1.7-1.8 mm long, 0.5-0.9 mm wide, glabrous. 2n = 36, (54), 72, (90).

Oplismenus hirtellus grows at scattered locations in the southeastern United States, extending south in subtropical and tropical habitats to Argentina. Scholz (1981) recognized 11 subspecies and two forms within the species, but they overlap, both morphologically and geographically. The key below includes two subspecies attributed to the Flora region. In addition, a variegated form is cultivated as an ornamental and sold as Panicum variegatum. A third taxon, O. undulatifolius, was treated by Scholz as a subspecies of O. hirtellus but treatment as a species seems more appropriate.

According to Scholz (1981), O. hirtellus subsp. fasciculatus U. Scholz is restricted to southern Louisiana and eastern Mexico; O. hirtellus subsp. setarius (Lam.) Mez ex Ekman is more widely distributed, growing both in the southeastern United States and Mexico. Oplismenus hirtellus subsp. undulatifolius (Ard.) U. Scholz was found recently in Maryland (Peterson et al. 1999); it is native to the Eastern Hemisphere.

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Oplismenus undulatifolius (Ard.) P. Beauv.

Plants perennial. Culms 20-50 cm takkm straggling, ascending from a prostrate base. Leaves: sheaths usually densely tuberculate-hairy, sometimes glabrous; ligules about 1 mm long; blades 1-15 cm long, 0.3-3 cm wide, glabrous or hairy, lanceolate to narrowly ovate, base somewhat rounded to oblique, tip acute. Panicles 9-15 cm long, glabrous or hispdulous; branches 4-9, up to 2 cm long, axes often setose, spikelets in 3-5 pairs. Spikelets lanceolate, hispidulous. Lower glumes 3-5-veined, awned, awn 5-10(15) mm long; upper glumes 5-veined, awned, awn 2-5 mm long; lower lemmas herbaceous, 5-9-veined, mucronate, mucro 1-2 mm long; upper lemmas subcoriaceous, smooth.

Oplismenus uyndulatifolius grows in moist, lightly shaded areas in forests. It is native in warm-temperate and subtropical regions of Asia, India, and Africa and has become an invasive weed in the eastern United States. It is treated in FNA 25 as a subspecies of O. hirtellus in accordance with the treatment by Scholz (1981) but differs in its shorter panicle branches as well as in being hairy. It is treated as a species in Australia and China. Preliminary results from work in the U.S. by Vanessa Beauchamp (Townson University) and Sharon Talley (APHIS). The description is taken from Chen and Phillips (2006).