Urochloa
Plants annual or perennial; usually cespitose, sometimes mat-forming, sometimes stoloniferous. Culms 5-500 cm, herbaceous, erect, geniculate, or decumbent and rooting at the lower nodes. Sheaths open; auricles rarely present; ligules apparently of hairs, the basal membranous portion inconspicuous; blades ovate-lanceolate to lanceolate, flat. Inflorescences terminal or terminal and axillary, usually panicles of spikelike primary branches in 2 or more ranks, rachises not concealed by the spikelets; primary branches usually alternate or subopposite, spikelike, and 1-sided, less frequently verticillate, axes flat or triquetrous, usually terminating in a well-developed, rudimentary spikelet; secondary branches present or absent, axes flat or triquetrous; disarticulation beneath the spikelets. Spikelets solitary, paired, or in triplets, subsessile or pedicellate, divergent or appressed, ovoid to ellipsoid, dorsally compressed, in 1-2(4) rows, with 2 florets, lower or upper glumes adjacent to the branch axes. Glumes not saccate basally; lower glumes usually 1/5 – 2/3 as long as the spikelets, occasionally equaling the upper florets, (0)1-11-veined; upper glumes 5-13-veined; lower florets sterile or staminate; lower lemmas similar to the upper glumes, 5-9-veined; lower paleas if present, usually hyaline, 2-veined; upper florets bisexual, sessile, ovoid to ellipsoid, usually plano-convex, usually glabrous, not disarticulating, mucronate or acuminate; upper lemmas indurate, transversely rugose and verrucose, 5-veined, margins involute, apices round to mucronate, or aristate; upper palea rugose, shiny or lustrous; lodicules 2, cuneate, truncate; anthers 3. Caryopses ovoid to elliptic, dorsally compressed; embryos 1/2 - 3/4 as long as the caryopses; hila punctate to linear, x = 7, 8, 9, or 10.
Distribution
Pacific Islands (Hawaii), Fla., Md., S.C., Puerto Rico, N.J., N.Mex., Tex., La., N.C., Ala., Ark., Tenn., Pa., Oreg., Okla., Va., Virgin Islands, Calif., Ill., Ga., Ariz., Mass., Mo., Kans., Miss., Ky.
Discussion
Urochloa is a genus of approximately 100 tropical and subtropical species. There are 19 species found in the Flora region. Eight species are established introductions, six are native, three are cultivated as grain or forage crops, and two have been found in the region but are not known to be established.
Urochloa differs from Moorochloa in its two or more ranks of panicles and rugose, non-disarticulating, distal florets. The rugose, often mucronate or aristate, distal florets also distinguish it from most species of Panicum.
Selected References
Lower Taxa
Key
| 1 | Branches at the lowest node of the inflorescence verticillate; inflorescences simple, open panicles, the primary branches with well-developed secondary and tertiary branches; plants perennial | Megathyrsus maximus |
| 1 | Branches at the lowest node of the inflorescence not verticillate; inflorescences usually with spikelike branches, secondary branches absent or inconspicuous, sometimes simple panicles; plants annual or perennial. | > 2 |
| 2 | Spikelets paired at mid-branch length, sometimes solitary distally. | > 3 |
| 3 | Axes of the primary panicle branches flat; lower glumes (0)1-3-veined. | > 4 |
| 4 | Plants annual; culms 10-35 cm tall; spikelets 1.8-2.2 mm long | Urochloa reptans |
| 4 | Plants perennial; culms 20-500 cm tall; spikelets 2.5-5 mm long. | > 5 |
| 5 | Upper lemmas awned, the awns 0.5-1.2 mm; lower glumes 3-veined, with 1-3 conspicuous, rigid hairs | Urochloa mosambicensis |
| 5 | Upper lemmas unawned; lower glumes 1-3-veined, glabrous | Urochloa mutica |
| 3 | Axes of the primary panicle branches triquetrous; lower glumes 3-7-veined. | > 6 |
| 6 | Spikelets 4.8-6 mm long; hila linear, about 1/2 as long as the caryopses | Urochloa texana |
| 6 | Spikelets 2-4.2 mm long; hila punctate. | > 7 |
| 7 | Branch axes densely hairy, the hairs papillose-based | Urochloa arizonica |
| 7 | Branch axes sometimes densely hairy, with few or no papillose-based hairs. | > 8 |
| 8 | Upper glumes with evident cross venation extending from near the bases to the apices; spikelets obovoid; upper glumes and lower lemmas usually glabrous; lower lemmas 7-veined | Urochloa fusca |
| 8 | Upper glumes without evident cross venation, or the cross venation confined to the distal 1/2; spikelets ellipsoid; upper glumes and lower lemmas glabrous or pubescent; lower lemmas 5-veined. | > 9 |
| 9 | Cauline nodes glabrous; plants 20-120 cm tall; spikelet apices abruptly acuminate | Urochloa adspersa |
| 9 | Cauline nodes pubescent; plants 10-70 cm tall, spikelets apices broadly acute to acute. | > 10 |
| 10 | Upper glumes 5-veined; upper lemmas 1.8-2.1 mm long; glumes separated by an internode about 0.3 mm long | Urochloa villosa |
| 10 | Upper glumes 7-9-veined; upper lemmas 2.3-3.3 mm long; glumes not separated by a conspicuous internode | Urochloa ramosa |
| 2 | Spikelets solitary at mid-branch length. | > 11 |
| 11 | Panicle branches triquetrous, 0.2-0.4 mm wide. | > 12 |
| 12 | Plants perennial; upper glumes (9) 11-13-veined; upper lemmas 2.4-2.8 mm long; glumes not separated by a conspicuous internode; lower florets staminate | Urochloa ciliatissima |
| 12 | Plants annual; upper glumes 5-veined; upper lemmas 1.8-2.1 mm long; glumes separated by an internode about 0.3 mm long; lower florets sterile | Urochloa villosa |
| 11 | Panicle branches flat or crescent-shaped in cross section, 0.5-2.5 mm wide. | > 13 |
| 13 | Upper lemmas awned, the awns 0.3-1.2 mm long, apices rounded. | > 14 |
| 14 | Plants perennial; lower glumes with 1-3 conspicuous, rigid hairs, the lower glumes 1/2 - 3/4 as long as the spikelet; lower florets staminate | Urochloa mosambicensis |
| 14 | Plants annual; lower glumes without conspicuous, rigid hairs; the lower glumes 1/4 - 1/3(1/2) as long as the spikelet; lower florets sterile | Urochloa panicoides |
| 13 | Upper lemmas unawned; apices variable, with or without a mucronate tip. | > 15 |
| 15 | Spikelets in a single row along the branches; spikelets 4-6 mm long; lower florets staminate; panicle branch axes crescent-shaped in cross section | Urochloa brizantha |
| 15 | Spikelets in 2 rows along the branches; spikelets 2.5-6 mm long; lower florets sterile or staminate; panicle branches flat. | > 16 |
| 16 | Lower glumes 5-7-veined; glumes scarcely separated, the internode between them shorter than 0.3 mm. | > 17 |
| 17 | Upper glumes and lower lemmas pubescent, the hairs often long in the distal 1/3 | Urochloa piligera |
| 17 | Upper glumes and lower lemmas glabrous. | > 18 |
| 18 | Plants perennial, stoloniferous; lower florets staminate | Urochloa arrecta |
| 18 | Plants annual; lower florets sterile | Urochloa platyphylla |
| 16 | Lower glumes (7)9-11-veined; glumes separated by a conspicuous, 0.3-0.5 mm internode. | > 19 |
| 19 | Lower paleas absent; spikelets usually pubescent, sometimes glabrous | Urochloa piligera |
| 19 | Lower paleas present; spikelets glabrous. | > 20 |
| 20 | Spikelets 3.3-3.7 mm long; base of blades rounded to subcordate, not clasping the stem | Urochloa subquadripara |
| 20 | Spikelets 4-6 mm long; base of blades subcordate to cordate, clasping the stem | Urochloa plantaginea |