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Support the Flora of the Southeastern US

2024 has been a banner year for making the best flora we can imagine. We've created:
With financial support from people like you, we are aiming even higher in 2025. Together we can accomplish all this: Vote on our 2025 priorities
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Key to Paspalum

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1 Both lower and upper glumes absent, or upper glume present on terminal spikelet only of a panicle branch.
  2 Plants stoloniferous; culms to 40 cm long; blades to 4 mm wide; spikelets 3.8-5.2 mm long, apex acuminate; upper glume sometimes present on terminal spikelet of a panicle branch
  2 Plants cespitose; culms to 200 cm long; blades to 35 mm wide; spikelets 1.8-2 mm long, apex obtuse; both glumes absent from all spikelets
1 At least upper glume present on all spikelets.
    3 Spikelets solitary, not associated with rudimentary spikelets or naked pedicels.
image of plant
Show caption*© Jay Horn
      4 Panicles usually composed of a terminal pair of branches, sometimes with 1 (-5) additional branches below the terminal pair.
        5 Upper glumes pubescent on the back or margins.
          6 Spikelets 1.3-1.9 mm long; upper glumes pilose along the margins; ligules 0.5-0.8 mm long; panicle branch axis 0.2-0.8 mm wide
          6 Spikelets 2.4-3.2 mm long; upper glumes sparsely pubescent on the back; ligules 1-2 mm long; panicle branch axis 1.2-2.2 mm wide
               8 Plants short-rhizomatous, culms appearing cespitose; blades to 4 mm wide; spikelets 3-3.6 mm long; lower lemmas 5-veined; upper florets stramineous to golden brown; most frequently found along roadsides and in pastures
               8 Plants rhizomatous, the culms separate; blades to 8 mm wide; spikelets 3-4.5 mm long; lower lemmas 3-veined; upper florets white; most frequently found in brackish and salt marshes
             7 Spikelets ovate to broadly elliptic, the tip obtuse to broadly acute.
                 9 Culms to 60 cm long; blades flat; panicle branches to 6.4 cm long; spikelets 1.9-2.3 mm long, 1.2-2 mm wide; upper glumes 3-veined
                 9 Culms to 120 cm long; blades flat or longitudinally folded; panicle branches to 15 cm long; spikelets 2.5-4 mm long, 2-2.8 mm wide; upper glumes 5-veined
image of plant
Show caption*© Kevin Faccenda, some rights reserved (CC BY), uploaded by Kevin Faccenda
      4 Panicles with 1-70 branches; if > 1, the branches arranged racemosely, the 2 uppermost not paired.
image of plant
Show caption*© Gary P. Fleming
                   10 Panicle branches 7-70, the axes extending beyond the outermost spikelets; panicle branches disarticulating at maturity
image of plant
Show caption*© Greg Tasney, some rights reserved (CC BY-SA), uploaded by Greg Tasney
                   10 Panicle branches 1-6, terminating in a spikelet; panicle branches persistent.
image of plant
Show caption*© Scott Ward
                       12 Axes of panicle branches not broadly winged, 0.6-1.3 mm wide.
                          13 Spikelets slightly longer than broad, 2.0-2.5 mm wide
image of plant
Show caption*© Dan Johnson, some rights reserved (CC BY), uploaded by Dan Johnson
                       12 Axes of panicle branches broadly winged, 1.8-3.3 mm wide.
                            14 Culms to 100 cm long; spikelets 3.2-4 mm long, 1.6-1.7 mm wide; upper lemmas with a few short hairs at their tips; caryopses 2-3 mm long
                            14 Culms to 50 cm long; spikelets 1.7-2.1 mm long 1.1-1.4 mm wide; upper lemmas glabrous; caryopses 1-1.3 mm long
    3 Spikelets paired, or at least the second nonfunctional spikelet represented by a naked pedicel.
                                16 Nodes glabrous; blades 1.9-8 mm wide; panicle branches 2-6; upper florets 0.8-1.1 mm long
                                16 Nodes pubescent; blades 10-24 mm wide; panicle branches 18-50; upper florets 1.1-1.3 mm long
                                  17 Margins of upper glumes and lower lemmas fimbriate, or ciliate with soft hairs 5 mm or more long.
                                    18 Culms to 70 cm long; upper glumes and lower lemmas broadly winged, the wing fimbriate; spikelets 2.4-3 mm wide
                                    18 Culms to 220 cm long; margins of upper glume and lower lemmas long-ciliate, wingless; spikelets 1.1-2.5 mm wide.
                                       19 Panicle branches (4-) 10-30; spikelets 1.8-2.8 mm long, 1.1-1.5 mm wide
                                           21 Plants either not aquatic OR if aquatic then with erect culms; lower glumes absent.
                                               23 Plants annual; axes of panicle branches broadly winged, the wings about as wide as the central portion; [common native]
                                               23 Plants perennial; axes of panicle branches narrowly winged, the wings narrower than the central portion; [rare exotics].
                                                 24 Blades 7-18 mm wide; axes of panicle branches 0.5-1.2 mm wide; spikelets 1.1-1.8 mm wide; upper florets 1.8-2.2 mm long
                                                 24 Blades 10-30 mm wide; axes of panicle branches 1-1.7 mm wide; spikelets 1.8-2.4 mm wide; upper florets 2.5-2.7 mm long
                                                      26 Blades to 15 mm wide; panicle branches 1-10 (-28); branch axes 0.7-2.3 mm wide; spikelets 2-2.2 mm long
                                                      26 Blades to 7 mm wide; panicle branches 2-8; branch axes 0.6-1.1 mm wide; spikelets 2.2-3 mm long.
                                                        27 Panicle branches 2-7, 1.6-7.1 cm long; spikelets 2.5-3 mm long, 1.5-2.2 mm wide; upper florets dark brown
                                                        27 Panicle branches 5-8, 3.5-11 cm long; spikelets 2.2-2.7 mm long, 1-1.4 mm wide; upper florets chestnut brown
                                                          28 Rhizomes indistinct or absent; ligule 1-4.1 mm long; panicle branches to 11 cm long; mature lower lemma not transversely rugose.
                                                              30 Plants annual; culms to 53 cm long; blades to 12 mm wide, flat; ligules 2-4.1 mm long; branch axes 0.8-1.3 mm wide; spikelets 2.1-2.6 mm long
                                                              30 Plants perennial; culms to 110 cm long; blades to 5.4 mm wide, usually conduplicate; ligules 2-3 mm long; branch axes 0.6-1.1 mm wide; spikelets 2.5-3 mm long
                                                                   32 Plants annual; ligules 0.1-0.3 mm long; blades to 13 cm long; panicle branches to 2.5 cm long; upper glumes and lower lemmas rugose
                                                                   32 Plants perennial; ligules 1-6.3 mm long; blades to 62 cm long; panicle branches to 13 cm long; upper glumes and lower lemmas smooth.
                                                                                                              52 Plants aquatic; blades to 10 mm wide; panicle branches ascending to erect, to 12 cm long; spikelets 2.5-3 mm long, 1.3-1.6 mm wide; lower glumes often present; upper glumes and lower lemmas with 5 veins
                                                                                                              52 Plants terrestrial; blades to 18 mm wide; panicle branches ascending to spreading, to 7.9 cm long; spikelets 2.8-3.6 mm long, 1.5-2 mm wide; lower glumes absent; upper glumes and lower lemmas with 3 veins.
                                                                                                                     55 Ligules to 2.2 mm long; blades to 8.3 mm wide; spikelets 2.1-3.1 mm long; upper glumes 3-veined; upper florets white, straminous, light yellow or golden brown.