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Key to Muhlenbergia

Poaceae

Muhlenbergia

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1 Panicle open and diffuse, > 4 cm broad, ultimately appearing broad and not spikelike (2.5-7 cm wide in M. texana, the pedicels still usually longer than the florets); the spikelets borne separately on slender or capillary pedicels longer than the lemmas or borne tightly and appressed on diverging spikelike branches.
  2 Spikelets mostly sessile, not borne on capillary pedicels, tightly appressed to the panicle branches; panicle branches strongly divergent; lemmas and midveins pubescent; [subgenus Bealia]
  2 Spikelets borne on slender or capillary pedicels (pedicellate), not appressed tightly to panicle branches, individual panicle branches not spikelike; branches primarily ascending (sometimes weakly divergent); lemmas and midveins .
    3 Spikelets 1.1-2.2 mm long, usually borne singly (occasionally spikelets with 2 or 3 florets).
      4 Culms compressed-keeled throughout, the internodes mostly glabrous but with strigose keels (M. torreyana) or puberulent to strigose pubescence below the nodes.
        5 Plants rhizomatous (not cespitose), the rhizomes prominent, creeping and covered with imbricate scales; keels of the culms and below nodes evidently strigose; leaf blades scabrous on both surfaces; lemmas 1.1-2.2 mm long; [subgenus “incertae sedis”]
        5 Plants lacking rhizomes, plants tufted (culms arising from the bases of older culms lying depressed); keels of the culm glabrous, the area below nodes glabrous or sometimes minutely puberulent (usually requiring magnification to see); leaf blades hirtellous above, smooth or scabridulous below; lemmas awnless; [subgenus Pseudosporobolus]
      4 Culms terete to somewhat compressed-keeled near the base, decumbent-ascending; internodes entirely glabrous (M. asperifolia)
          6 Plants delicate annuals; culms decumbent-ascending, the internodes entirely glabrous; panicles broadly ovoid, not much longer than wider (6-21 cm long, 4-16 cm wide), the branches spreading
          6 Plants rhizomatous perennials; culms erect, the internodes strigulose; panicles distinctly longer than wide (9-21 cm long, 2-7 cm wide), the branches narrowly ascending to slightly divergent
    3 Spikelets 2.5-5 mm long (excluding awns); spikelets with 1 floret.
             7 Culms geniculate, the vegetative branches widely divergent, the plant appearing bushy in form
             7 Culms erect to somewhat decumbent but the (vegetative) branches not widely divergent.
               8 Culms 20-60 (-70) cm, somewhat decumbent, the leaves concentrated somewhat basally
               8 Culms (40-) 60-150 cm, stiffly erect from the base, with pronounced cauline leaves; [subgenus Trichochloa; add M. ×involuta].
                 9 Lemmas shiny; culms 40-80 cm tall; panicles about as long as wide; branches and pedicels stiff or flexible; ligules lacerate; [endemic to OK and TX]
                 9 Lemmas not shiny; culms 60-150 cm tall; panicles longer than wide; branches and pedicels flexible; ligules decurrent; [collectively widespread, including OK and TX].
                   10 Lemma awn 0-1.5 (-4) mm long; glume bodies (1.1-) 2.0-3.3 (-3.6) mm long, > ½ as long as the lemma bodies, acuminate, not awned (rarely the second with a short awn < 0.6 mm long); spikelets usually brown or bronze (when fresh); basal sheaths usually very fibrous
                   10 Lemma awn (2-) 3-35 mm long; glume bodies (0.3-) 0.7-1.7 (-2.4) mm long, < ½ as long as the lemma body, one or both glumes sometimes awned; spikelets usually purple (when fresh); basal sheaths rarely strongly fibrous.
                     11 Lemma awn (2-) 3-13 (-18) mm long, first glume awnless (or rarely with an awn to 3.2 mm long), second glume awnless (or rarely with an awn up to 5.0 mm long), palea awnless; lemma lacking setaceous teeth flanking the awn; flowering late Aug-Oct; [widespread in our area, particularly in rocky, clayey, or sandy glades, barrens, and woodlands with prairie affinities]
                     11 Lemma awn (8-) 12-26 (-35) mm long, first glume awn (0.5-) 1-7 (-10) mm long, second glume awn (1-) 5-19 (-25) mm long, palea awn-tipped; lemma with two setaceous teeth flanking the awn, the teeth 0.5-2.5 (-4.7) mm long; flowering Oct-Nov; [sandy maritime situations on barrier islands of the outer Coastal Plain]
1 Panicle slender, dense, < 2.5 cm broad, usually appearing spikelike; spikelets sessile or on non-capillary pedicels shorter than the lemmas.
                       12 Spikelets arranged in pairs on short, unequal pedicels ca. 1-2 mm long, therefore the paired spikelets usually disarticulating as "units"; lower glumes usually 2-awned, the awns 1-3.5 mm long; [subgenus Pseudosporobolus]
                       12 Spikelets not arranged in pairs, disarticulating singly; [subgenus Muhlenbergia].
                          13 Glumes minute, 0-0.5 mm long; plant lacking rhizomes; culms weak, decumbent and cespitosely branching in their lower portions (rooting at the nodes), the upper portions erect and sparsely branched
                          13 Glumes well-developed, (0.8-) 1.0-8.0 mm long (if < 1.0 mm then other characters not also as above); plants with scaly rhizomes OR cespitose and lacking rhizomes (if rooting at the nodes then glumes at least 1 mm long); culms variously decumbent to erect, although usually at least somewhat firm; {add M. xcurtisetosa, M xinvoluta}
                            14 Spikelets and glumes both 3-8 mm long (the glumes tapered to arched or straight awns), 1.3-2x the length of the lemma (excluding its awn); panicle dense and spike-like, 0.8-16 cm long and 0.3-10 mm broad.
                              15 Culms with little to no branching above the base; internodes dull and puberulent, strigose directly below the nodes; awns of the glumes to 5 mm long; ligules 0.2-0.6 mm long
                              15 Culms much-branched above the base; internodes smooth, polished, and mostly glabrous (sometimes puberulent directly below the nodes); awns of the glumes to 1 mm long; ligules 0.6-1.7 mm long
                            14 Glumes 0.5-3 mm long, unawned or mucronate (occasionally bifid), shorter than to barely exceeding the lemma; panicle usually slender and ascending, often with some elongated (though appressed) branches, 4-50 cm long, 2-15 cm wide (much thinner in M. utilis and sometimes M. lindheimeri, if so then the spikelets never >3.5 mm long and in M. lindheimeri, the culms also then basally compressed-keeled)
                                  17 Internodes puberulent for most of their length, strigose below the nodes; lemma awns 7-12 mm long; spikelets 2.2-3.7 mm long, loosely clustered (not overlapping)
                                  17 Internodes pubescent for most of their length, retrorsely hirsute or strigose below the nodes; lemma awns 1-11 mm long (rarely awnless); spikelets 2.6-3.5 mm long, tightly clustered (spikelets often overlapping at least somewhat with adjacent spikelets)
                                16 Internodes entirely glabrous (M. bushii and M. frondosa) or mostly so (often shiny), sometimes the area immediately below nodes scabridulous, hispidulous or puberulent, but the internodes not pubescent throughout; panicles 0.1-3.0 mm wide; pedicles glabrous, scabrous, or strigulose or strigose.
                                    18 Plants cespitose (clumped), lacking rhizomes, either an annual (M. tenuifolia) or a cespitose perennial (with knotty bases in M. cuspidata).
                                       19 Panicles 15-50 cm long; basal sheaths compressed-keeled; spikelets light gray, the glumes occasionally bifid with teeth to 0.3 mm long; [subgenus Trichochloa; TX south to n. Mexico]
                                       19 Panicles 7-20 cm long (if < 15 cm long, then the inflorescence lax or nodding and with both terminal and axillary panicles as in M tenuifolia) basal sheaths not compressed-keeled; spikelets dark green, dull gray, or purplish, the glumes never bifid but sometimes mucronate; [collectively widespread, including TX
                                         20 Plants cespitose perennials with knotty bases (sometimes slender stolons); culms always hispidulous immediately below the nodes; panicles 0.1-0.8 cm wide; lemmas awnless or sometimes with a mucro to 0.3 mm long, sometimes mottled greenish-black; callous glabrous; [calcareous cliffs and outcrops]
                                         20 Plants annual or short-lived perennials, lacking knotty bases; culms always scabridulous immediately below the nodes; lemmas with awns 10-30 mm long, often purplish but not mottled greenish-black; inflorescence compound, with terminal and axillary panicles; callous bearded; [woodlands and grasslands]
                                    18 Plants rhizomatous perennials, not or very rarely cespitose, with well-developed and often scaly rhizomes.
                                             22 Lemmas pubescent (sometimes only on the calluses, but evident); internodes not entirely glabrous, usually scabridulous to strigose immediately below the nodes (occasionally smooth in M. mexicana); glumes 1.5-3.7 mm long; grain 1.1-1.6 mm long.
                                               23 Panicles 0.2-0.8 cm wide, the axillary panicles partially included in or exserted from subtending sheaths, the pedicels scabrous to strigulose; lemmas usually entirely glabrous (rarely with a few appressed hairs), unawned; spikelets primarily green
                                               23 Panicles 0.3-3.0 cm wide, the axillary panicles long exserted, the pedicels strigose; lemma pilose basally (sometimes restricted to the callus), unawned or with awns to 10 mm long; spikelets often purple-tinged
                                                 24 Internodes and culms entirely glabrous (including immediately below the nodes); glumes 1.4-2.0 mm long; ligule 0.2-0.5 mm long, ciliolate; [subgenus Muhlenbergia]
                                                    25 Culms 25-95 cm tall; culms internodes mostly glabrous and shiny, scabridulous immediately below the nodes; leaf blades 4-16 cm long, 2-7 mm wide, flat, the ligules ciliolate; panicles 4-18 cm long, the pedicels strigose; lemms awnless or with awns to 1 mm; [subgenus Muhlenbergia]
                                                    25 Culms 7-30 cm tall; culm internodes mostly glabrous to slightly nodulose, glabrous or minutely pubescent immediately below the nodes; leaf blades 0.5-4.7 cm long, 0.2-1.8 mm wide, often involute, the ligules not ciliolate; panicles 1-5 cm long, the pedicels glabrous; lemmas awnless; [subgenus Pseudosporobolus]