Flora of the Southeastern United States

1 Spikelets tuberculate or tuberculate-hispid, appearing conspicuously "warty"

1 Spikelets variously glabrous to pubescent but lacking a conspicuously tuberculate (warty) appearance.

  2 Panicle < 2 cm wide at maturity.

    3 Spikelets > 4.5 mm long; first glume > 2.4 mm long; ligule 4-6 mm long; [of coastal dunes]; [Panicum section Hiantes]

    3 Spikelets < 4 mm long; first glume < 2.1 mm long; ligule < 2 mm long; [not of coastal dunes].

      4 Blades involute, 1.5-4 mm wide; culms wiry

      4 Blades flat, the larger 2-20 mm wide; culms stout.

        5 Panicles constricted, 0.3-1.6 cm wide; spikelets subsessile to short-pediceled; summit of fertile palea not enclosed by fertile lemma

        5 Panicles > 1 cm wide; spikelets short to long-pediceled; summit of fertile palea enclosed by fertile lemma

  2 Panicle > 2 cm wide at maturity.

          6 Lower primary panicle branches in whorls of 4-7 at the nodes, stiffly spreading, naked on the proximal ½, the axils strongly pilose; lower culm internodes appressed papillose-pubescent; first glume acuminate, ½ as long as spikelet; fertile lemma chestnut brown at maturity; [Panicum section Panicum]

          6 Plants without the above combination of characters.

             7 Plants from a cluster of fibrous roots, lacking rhizomes or hard knotty crowns, annuals or perennials.

               8 First glume 1/5 to 1/3 length of spikelet, blunt to broadly rounded to truncate; sheaths usually glabrous (papillose-hispid in P. dichotomiflorum var. bartowense); nodes glabrous; [Panicum section Dichotomiflora].

                 9 Plants perennial, aquatic and often floating, rooting at the lower nodes; leaf blades 2-15 mm wide.

                 9 Plants annual, terrestrial; leaf blades 3-25 mm wide.

                   10 Spikelets ovoid to slenderly ellipsoid, 1.6-2.3 mm long, widest at middle with acute tips, second glume and sterile lemma thin, submembraneous; some to many pedicels > 3 mm long and longer than spikelets; culms to 6 dm long; leaf blades 1-8 mm wide

                   10 Spikelets oblong-lanceolate, (2.0-) 2.4-3.6 mm long, widest below middle, tapering to acuminate tips, second glume and sterile lemma firm, subcoriaceous; most pedicels < 3 mm long and shorter than spikelets; culms to 20 dm long; leaf blades 4-20 mm wide.

                     11 Sheaths conspicuously papillose-hispid; ligule 1.5-3 mm long; mature plant stout, erect, usually 10-20 dm long; spikelets 2.3-2.8 mm long

                     11 Sheaths glabrous to sparsely pilose, the hairs not papillose-based; ligule 1-2 mm long; mature plant usually spreading to ascending, 5-10 (20) dm long; spikelets 2.3-3.8 mm long

               8 First glume 1/3 to 1/2 length of spikelet, acute to subacute (sometimes 3/4 the length in P. hirticaule); sheaths villous, hirsute or hispid (except in the locally introduced P. bisulcatum); nodes often bearded.

                       12 Spikelets 4.5-6 mm long; panicle branches often nodding or drooping at maturity; [Panicum section Panicum].

                          13 Mature upper florets tan to orangish, not disarticulating; culms 2-12 dm tall; panicles usually nodding, not fully exserted, > 2× as long as wide; panicle branches ascending to appressed; pulvini well-developed

                          13 Mature upper florets blackish, disarticulating at maturity; culms 7-21 dm tall; panicles erect, exserted at maturity, about 2× as long as wide; panicle branches ascending to spreading; pulvini well-developed

                       12 Spikelets 1-4 mm long; panicle branches ascending to spreading at maturity (occasionally reflexed, as in P. trichoides, if so spikelets then also < 4 mm long).

                            14 Both the internodes and culms entirely glabrous; [Panicum section Monticola]

                            14 Internodes and culms not both glabrous (at least the nodes and/or internodes with some pubescence).

                              15 Plants perennial; leaf blades with prominent white midrib; [wet habitats from s. TX southward]; [Panicum section Panicum]

                              15 Plants annual; leaf blades with or without prominent white midrib (instead often, but not always, hyaline); [habitats dry to wet, collectively widespread but largely absent from s. TX (except P. capillare)].

                                16 Spikelets 1.0-1.4 mm long, 0.5-0.6 mm wide; internodes pilose; leaf blades 2-7 cm long; [TX southward]

                                16 Spikelets 1.4-4.2 mm long, (0.5-) 0.6-1.1 mm wide (1.4-2.4 mm long and 0.5-0.7 mm wide in P. philadelphicum complex); internodes glabrous to densely pilose; leaf blades 3-40+ cm long; [collectively widespread, including TX].

                                  17 Mature panicle slender, usually at least 1/2 as long as the plants and ca. 3x as long as wide, the panicle branches primarily ascending to slightly divergent (spreading); spikelets narrowly ovoid, the tips acuminate; nodes densely pilose; [plants of dry or often wet calcareous habitats (e.g., fens); the habitats often somewhat conservative]; [Panicum section Panicum]

                                  17 Mature panicle broader, 0.7-2x as long as wide, < 1/2 the total height of the plant (except P. capillare), the panicle branches divergent (spreading); spikelets acute, subacute or if sometimes acuminate (P. philadelphicum; P. hirticaule) then the spikelets ovoid or spherical in shape; nodes glabrous to densely pilose; [plants of various habitats, usually open and somewhat disturbed].

                                    18 Culms 10-70 cm tall; panicles 5-8 cm wide; spikelets 1.9-3.3 mm long, ovoid or spherical in shape; nodes shortly hirsute or glabrous (although sheaths sometimes hispid with papillose-based hairs)

                                    18 Culms 15-130 cm tall; panicles 4-24 cm wide; spikelets 1.4-4.0 mm long, ellipsoid to lanceoloid or sometimes narrowly ovoid in shape; nodes sparsely to densely pilose (the sheaths with papillose-based hairs).

                                       19 Panicle usually equal to or longer than portion of culm below panicle, often basally included at maturity; panicle rachis, branches, and pedicels usually scabrous with barbs > 0.05 mm; pulvini usually pilose to villous, especially at lower primary branches (sometimes glabrous); culm usually not obviously zig-zag; larger blades usually more than 10 mm wide; spikelets 1.6-2.9 (-4) mm long, short- to long-acuminate, lanceolate, lance-ovoid, or lance-ellipsoid; first glume 0.6-1.5 (-2) mm long; [Panicum capillare complex]

                                         20 Upper florets lacking a lunate (crescent-shaped) scar and usually stramineous (straw-colored); secondary branches conspicuously diverging; [widespread, including KS, OK and TX]

                                         20 Upper florets with a lunate scar present at the bases, usually black to grey in color; secondary branches of the panicles often appressed; [KS, OK and TX in our flora area]

                                       19 Panicle usually not as long as portion of culm below panicle, usually exerted at maturity; panicle rachis and branches usually smooth, the pedicels often scabrous with barbs < 0.05 mm; pulvini glabrous to sparsely (-moderately) pilose; culm often zig-zag at least proximally; larger blades usually no more than 4-12 mm wide; spikelets 1.4-2.4 mm long, pointed to short-acuminate, lance-ellipsoid, ellipsoid, ovoid, or obovoid; first glume 0.4-0.9 (-1.2) mm long; [Panicum philadelphicum complex].

                                           21 Herbage usually purple-tinged (-yellowish-green); internodes glabrous to sparsely hispid; blades 2-6 mm wide, ascending; pulvini glabrous to sparsely pilose; spikelets 1.8-2.2 mm long, twice or more as long as wide; mature fertile lemma blackish (rarely stramineous); [plants of granite outcrops of NC, SC, and GA]

                                           21 Herbage yellow-green to green or purple-tinged; internodes glabrate to densely hispid; blades 2-12 mm wide, spreading to ascending; pulvini glabrous to pilose; spikelets 1.4-2.4 mm long, < 2 to 2 × as long as wide; mature fertile lemma stramineous to blackish; [plants of a variety of open or wooded, dry or wet, and often disturbed sites].

                                             22 Culms to 1 m long; internodes sparsely to densely hispid; blades to 12 mm wide; blade of flag (inflorescence bract) usually > ½ as long as panicle; panicle ellipsoid to obovoid, moderately to densely flowered; pulvini glabrous to sparsely pilose; spikelets 1.7-2.4 mm long

                                             22 Culms to 0.5 m long; internodes glabrate to hispid; blades to 6 mm wide; blade of flag (inflorescence bract) usually < ½ as long as panicle; panicle ovoid to deltoid, sparingly to moderately flowered; pulvini sparsely to moderately pilose; spikelets 1.4-2.2 (-2.4) mm long

             7 Plants with rhizomes or hard knotty crowns, perennial.

                                               23 Plants with hard or knotty crowns, lacking rhizomes (crowns sometimes partially concealed by old leaf bases).

                                                 24 Spikelets 5.0-6.5 mm long, long acuminate; internodes densely pubescent

                                                 24 Spikelets < 4.5 mm long, acute to short-acuminate; internodes glabrous to pubescent (if pubescent then spikelets never exceeding 4.5 mm in length)

                                                    25 Nodes sericeous, pilose, or glabrous; internodes often glaucous; spikelets usually appressed but not secund; pedicels 1-15 mm long; second glumes and sterile lemmas 7-11-veined; fertile lemmas 0.7-1.2 mm wide; [Panicum section Panicum]

                                                      26 Spikelets 3.0-4.2 mm long, relatively sparse within the panicles; leaves generally basally clustered, the panicles therefore usually far exceeding the tips of the upper leaf blades

                                                      26 Spikelets 2.1-3.0 mm long, relatively dense within the panicles; leaves generally not basally clustered, the panicles therefore scarsely exceeding the tips of the upper leaf blades

                                                    25 Nodes glabrous; internodes not glaucous; spikelets appressed, usually secund; pedicels 0.5-1.5 mm long; second glumes and sterile lemmas 5-veined; fertile lemmas 0.6-0.8 mm wide

                                               23 Plants with rhizomes (these sometimes short and knotty but still evident).

                                                        27 Rhizomes less than 1 cm thick with glabrous scale-like leaves; culms not woody (except semi-woody at the base in P. hirsutum).

                                                          28 First glume truncate apically (subacute in P. gouinii); [Panicum section Repentia].

                                                            29 Panicle dense, with purplish spikelets; first glume triangular to subacute, ca. 1/3rd the length of the spikelet

                                                            29 Panicle loosely flowered; first glume truncate, ca. 1/5th the length of the spikelet

                                                          28 First glume acute to obtuse.

                                                              30 Culms slightly compressed below; ligules 0.5 mm long or less; spikelets subsessile and subsecund, usually some obliquely bent above the first glume

                                                              30 Culms terete; ligules (0.5-) 1-6 mm long (if sometimes < 1 mm as in P. coloratum and P. diffusum, then culms not compressed); spikelets pedicelled and not at all secund, essentially straight.

                                                                 31 Nodes pilose to pilose-sericeous, the internodes also often with papillose-based hairs (usually at least some hairs present directly below the nodes in P. hirsutum); [LA and TX only in our flora area]; [Panicum section Panicum].

                                                                   32 Sheaths hispid but lacking irritating hairs; culms spreading to weakly ascending, never slightly woody at the base, ca. 6-100 cm tall and 0.5-3.5 mm thick

                                                                   32 Sheaths with prickly, irritating hairs (grab carefully); culms decumbent, semi-woody at the base, ca. 100-300+ cm tall and 4-10 mm thick

                                                                 31 Nodes glabrous or puberulent, the internodes also glabrous; [collectively widespread, including LA and TX].

                                                                     33 Lower glumes 0.5-1.5 mm long, < 1/2 as long as the spikelets; upper glumes and lower lemmas scarsely gaping; [Panicum section Repentia]

                                                                     33 Lower glumes 1.8-4.0 mm long, > 1/2 as long as the spikelets; upper glumes and lower lemmas clearly gaping; [Panicum section Hiantes].

                                                                       34 Panicle narrow, the branches erect; sheaths longer than internodes; spikelets 4.3-7.7 mm long; fertile lemma 3-4 mm long.

                                                                         35 First glumes 2.5-5.5 mm long, 2/3-3/4 as long as the spikelet, 7-9 nerved, the nerves thickened and raised; rhizomes usually elongate; culms solitary to loosely tufted, 0.2-1.5 m tall; leaves 0.7-3.6 dm long; panicles 2-6 cm wide, the primary branches usually 1-2 per node, loosely flowered; spikelets 4.7-7.7 mm long; fertile lemma 1.3-1.8 mm wide

                                                                         35 First glumes 2-3.5 mm long, 1/2-2/3 as long as the spikelet, 3-5 (-7) nerved, the nerves thin and wiry; rhizomes usually short; culms usually tufted, 1-2 (-3) m tall; leaves 2-5 dm long; panicles 3-10 cm wide, the primary branches usually 2 or more per node, densely flowered; spikelets 4.0-5.9 mm long; fertile lemma 1.0-1.5 mm wide

                                                                       34 Panicle with divergent to spreading-ascending branches; upper sheaths shorter than internodes; spikelets 2.8-5 mm long; fertile lemma 2-2.6 mm long.

                                                                           36 Spikelets 2.8-3.5 mm long; beak of sterile lemma exceeding fertile lemma by 0.2-0.5 mm; first glume (blunt-) acute, ½-2/3× as long as spikelet

                                                                           36 Spikelets 3.2-5 mm long; beak of sterile lemma exceeding fertile lemma by 0.6-1.3 mm; first glume acuminate, 3/5-3/4× as long as spikelet.

                                                                              37 Rhizomes short, densely interlocking, culms subascending at base, densely clumped

                                                                              37 Rhizomes elongate, or if short, then culms horizontally divergent at base, loosely clumped