Flora of the Southeastern United States

1 Awn 2-3 mm long, straight or nearly so, scarcely (or not at all) exserted beyond the tips of the glumes; lemmas smooth, shiny; leaf blades flat or folded at the midvein (V-shaped in cross-section); ligule 3-10 (-17) mm long

1 Spikelets disarticulating below the glumes, the spikelets falling as a whole or in clusters; [tribe Poeae]

1 Spikelets disarticulating above the glumes, the glumes remaining attached to the pedicel.

  2 Spikelets dimorphic, paired, each pair consisting of a lower spikelet with sterile florets and an upper spikelet one with fertile florets; [tribe Poeae]

  2 Spikelets monomorphic.

    3 Spikelets each with 1 fertile (bisexual) floret, with 1-several sterile florets, either towards the base or towards the tip of the spikelet.

      4 Fertile floret basal, with 1-several sterile florets towards the tip of the spikelet; [tribe Cynodonteae; subtribe “incertae sedis”]

      4 Fertile floret terminal, with 1-several sterile florets towards the base of the spikelet (the sterile florets sometimes knoblike or like tufts of hairs, and not obviously like florets); [tribe Poeae].

        5 Spikelets with 2 florets, the lower floret staminate and of similar size as the upper, pistillate or bisexual floret; lemma of the lower floret awned; lemma of the upper floret unawned or awned

        5 Spikelets with 2-3 florets, the lower 1-2 florets staminate or sterile, either highly reduced to knobs or tufts of hairs, or shorter than to longer than the terminal, bisexual floret; lemma of the lower florets either awned or unawned; lemma of the upper floret unawned.

          6 Lower sterile florets 2, shorter than to exceeding the bisexual floret; fresh leaves with sweet vanilla odor when crushed; lemma of the lower florets awned or unawned

             7 Glumes unequal, the lower shorter than the upper; lowest 2 florets sterile.

             7 Glumes subequal; lowest 2 florets staminate.

          6 Lower sterile florets 1-2, either highly reduced to knobs or tufts of hairs, or consisting of linear to lanceolate lemmas up to ¾ as long as the bisexual floret; all lemmas unawned

    3 Spikelets each with 2 or more fertile florets.

               8 Spikelets 18-50 mm long; glumes 9-11-veined; [tribe Poeae]

               8 Spikelets 2.5-20 mm long; glumes 1-7-veined.

                 9 Lemma awns apical or dorsal (arising from the apex or back of the lemma or sometimes the midvein prolonged into a 1 mm awn), or sometimes awns absent (Rostraria).

                   10 Spikelets 7-20 mm long, with 3-12 florets; ligule of hairs; lemma awn 5-15 mm long; [collectively widespread in our area]; [tribe Danthoniae]

                   10 Spikelets 2.5-7.5 mm long, with 2-3(-6) florets; ligule membranous, sometimes ciliolate (only ciliolate in Rostraria) but otherwise not only consisting of hairs, 0.5-4 mm long; lemma awn 1-9 mm long; [tribe Poeae].

                     11 Lower lemmas irregularly hirsute or with conspicuous papillose-based hairs

                     11 Lemmas glabrous to scabrous, sometimes pilose but lacking papillose-based hairs or not irregularly hirsute.

                       12 Awns of the lemmas 1 mm long, essentially a minute prolonged extension of the lemma midvein; lemma apices acute

                       12 Awns of the lemmas 2-8 mm long, therefore conspicuous and not merely a minute midvein extension, bent or geniculate and often basally-twisted and exceeding lemma apices; lemma apices bifid or bicuspidate.

                          13 Panicle branches densely pubescent, usually glistening yellowish-brown or yellowish to tan; panicles either 1-5 cm (Trisetum aureum) OR 5-20 cm long (Trisetum flavescens); leaves evenly distributed; ligules 0.5-1(2) mm, obtuse, lacerate, sometimes ciliolate; plants sometimes with rhizomes to 7 cm long (T. flavescens); [occurring very sporadically in disturbed sites throughout our area or as a ballast waif in NJ]

                          13 Panicles branches glabrous or sparsely pubescent, usually silvery-shiny; panicles (5)20-30(50) cm long; leaves mostly basal or evenly distributed; ligules 0.5-4 mm, truncate or rounded; plants not rhizomatous; [a native of cool, moist, undisturbed northern sites; rare and disjunct in high elevation areas s. to VA]

                 9 Lemma awns basal (arising from the lower half of the lemma); [tribe Poeae].

                            14 Awns geniculate and articulated near the middle joint with a ring of minute conical protuberances, the distal segment of the lemma clavate and differing in shape from the proximal lemma segment; [NJ and PA northward]

                            14 Awns straight or geniculate (sometimes only slightly so), if geniculate then the awn not bearing a distinct ring at the joint and not bearing a clavate distal segment; [collectively widespread].

                              15 Rachilla glabrous, not prolonged beyond the upper floret; spikelets 1.7-3.8 mm long

                              15 Rachilla hairy, prolonged beyond the upper floret as a bristle; spikelets 2.5-7 mm long

                                16 Lemma awn 2-3 mm long, straight or nearly so, scarcely (or not at all) exserted beyond the tips of the glumes; lemmas smooth, shiny; leaf blades flat or folded at the midvein (V-shaped in cross-section); ligule 3-10 (-17) mm long