Flora of the Southeastern United States
2022 Edition

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Keyed in multiple places:

Key to Poaceae, Key C: bur, bead, or bulblet grasses of various tribes

1 Fertile spikelets absent (spikelets modified into asexual, purplish bulblets) or variously spiny or bead like; [tribe Poeae]
 Poa
1 Fertile spikelets variously spiny or bead-like.
..2 Pistillate spikelets concealed within a hard, beadlike shell, this white, black, or variously colored; [tribe Andropogoneae]
..2 Spikelets concealed in a variously spiny bur, this green or tan, sometimes with pink or purple shading.
....3 Bur formed from accrescent branchlets, with fewer and less regularly arranged straight prickles (these typically retrorsely scabrous); [tribe Paniceae]
....3 Bur formed from an enlarged glume, with 5-7 rows of hooked prickles; [tribe Cynodonteae; subtribe Traginae]

Key to Poaceae, Key F: grasses of tribe Paniceae (also including grasses keyed as well in Keys B, C, D, and H)

1 Inflorescences spikelike branches, the spikelets partially embedded in the rachises
1 Inflorescences panicles or spikes (if spikes, the spikelets not embedded.
..2 Spikelets (at least the terminal) subtended by 1-many stiff, terete bristles.
....3 Bristles persistent on the inflorescence, each spikelet disarticulating above the bristles
....3 Bristles falling with the spikelets at maturity (the disarticulation at the base of the fascicles)
..2 Spikelets not subtended by stiff bristles.
......4 Inflorescences of spikelike branches 1-3.7 cm long, the branch extending 2.5-4 mm beyond the attachment of the distal spikelets
......4 Inflorescences not as above.
........5 Upper florets laterally compressed
........5 Upper florets dorsally compressed.
..........6 Lower glumes or lower lemmas awned.
............ 7 Leaves > 10× as long as wide; ligules absent or of hairs
............ 7 Leaves < 8× as long as wide; ligules present, membranous or of hairs.
............ ..8 Lower glumes unawned or very shortly so; upper glumes ciliate-margined; plants erect or basally decumbent
............ ..8 Lower glumes awned; upper glumes not ciliate-margined; culms trailing; plants strongly trailing, rooting at the nodes
..........6 Lower glumes and lower lemmas unawned.
............ ....9 Lemma margins flat, hyaline; lower glumes absent or < ¼ the length of the upper glume.
............ ......10 Subterranean (cleistogamous) inflorescences present; aerial inflorescences with elongate rachises; spikelets of the aerial inflorescences often sterile; spikelets glabrous; leaves either with a white cartilaginous margin or prominently ciliate; [of the Coastal Plain]
............ ......10 Subterranean inflorescences absent; aerial inflorescences either with digitate or subdigitate branches and glabrous spikelets, or with elongate rachises and conspicuously pubescent spikelets; spikelets of the aerial inflorescences fertile; spikelets glabrous, ciliate, or pubescent; leaves various (often not as above); [collectively widespread]
............ ........11 Inflorescence a narrow panicle with the branches strongly ascending to appressed; spikelets ellipsoid to obovoid; [of Coastal Plain pinelands]
............ ........11 Inflorescence either a panicle with digitate or subdigitate clusters of spikelike branches or a broad panicle with widely divergent branches; [widespread]
............ ....9 Lemma margins not hyaline, frequently involute; lower glumes various (absent, < ¼ the length, to longer than the upper glume).
............ ..........12 Spikelets subtended by a cuplike callus
............ ..........12 Spikelets not subtended by a cuplike callus.
............ ............ 13 Leaves primarily lacking ligules (at least the upper, and often all, leaves without ligules, if vestigial ligules present, these of hairs)
............ ............ 13 Leaves with ligules, these either membranous or of hairs.
............ ............ ..14 Lower (sterile) palea indurate and expanding the spikelet at maturity, as long as the lower (sterile) lemma; lower and upper florets standing apart from one another at maturity; outer surface of the upper (fertile) palea with compound papillae
............ ............ ..14 Lower (sterile) palea membranous, not expanding the spikelet at maturity, usually shorter than lower (sterile) lemma, or absent; lower and upper florets closely appressed at maturity; outer surface of the upper (fertile) palea lacking compound papillae.
............ ............ ....15 Inflorescence of 1-sided, spikelike primary branches.
............ ............ ......16 Spikelets with lower lemmas (and lower glumes, if present) adjacent to the branch axes.
............ ............ ........17 Lower glumes absent
............ ............ ........17 Lower glumes present on at least most spikelets
............ ............ ......16 Spikelets with upper lemmas (and upper glumes, if present) adjacent or appressed to the branch axes.
............ ............ ..........18 Both glumes absent from all or most spikelets
............ ............ ..........18 Upper or both glumes present on all spikelets.
............ ............ ............ 19 Lower glumes usually absent; upper lemmas smooth to slightly rugose
............ ............ ............ 19 Lower glumes present; upper lemmas rugose and verrucose
............ ............ ....15 Inflorescence either paniculate with well-developed secondary branchlets or if the primary branches spikelike, then the spikelets not borne in a 1-sided arrangement on the spicate branches.
............ ............ ............ ..20 Inflorescences dense, the spikelets obscuring most of the internal branches
............ ............ ............ ..20 Inflorescences open panicles, or if narrowed, all or nearly all the panicle branches readily visible.
............ ............ ............ ....21 First glume 5-7.5 mm long, nearly as long as sterile lemma; fertile lemma 1/3 length of sterile lemma; rachilla prolonged between the florets
............ ............ ............ ....21 First glume shorter, or if this long, then at most 3/4 length of sterile lemma; fertile lemma > ½ the length of the sterile lemma; rachilla not prolonged between the florets.
............ ............ ............ ......22 Plant developing a terminal (“spring”) inflorescence usually before mid-summer, followed by lateral (“autumnal”) inflorescences from lower, mid, and/or upper nodes, these often included or hidden among the fascicles of smaller “autumnal” leaves; often developing a rosette of overwintering basal leaves
............ ............ ............ ......22 Plant developing a terminal inflorescence usually after mid-summer, the lateral inflorescences, when present, from the upper nodes, usually appearing at the same time as the terminal panicle, and not hidden by dense fascicles of smaller leaves; plants lacking a rosette of overwintering basal leaves.
............ ............ ............ ........23 Spikelets tuberculate
............ ............ ............ ........23 Spikelets smooth, not tuberculate.
............ ............ ............ ..........24 Panicle < 2 cm wide at maturity.
............ ............ ............ ............ 25 Spikelets > 4.5 mm long; first glume > 2.4 mm long; ligule 4-6 mm long; [of coastal dunes]
............ ............ ............ ............ 25 Spikelets < 4 mm long; first glume < 2.1 mm long; ligule < 2 mm long; [not of coastal dunes].
............ ............ ............ ............ ..26 Blades involute, 1.5-4 mm wide; culms wiry
............ ............ ............ ............ ..26 Blades flat, the larger 6-20 mm wide; culms stout.
............ ............ ............ ............ ....27 Panicles constricted, 0.3-1.6 cm wide; spikelets subsessile to short-pediceled; summit of fertile palea not enclosed by fertile lemma
............ ............ ............ ............ ....27 Panicles > 1 cm wide; spikelets short to long-pediceled; summit of fertile palea enclosed by fertile lemma
............ ............ ............ ..........24 Panicle > 2 cm wide at maturity.
............ ............ ............ ............ ......28 Fertile lemmas rugose with cross-venation between the main parallel veins
............ ............ ............ ............ ......28 Fertile lemmas not rugose.
............ ............ ............ ............ ........29 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
............ ............ ............ ............ ........29 Plants without the above combination of characters.
............ ............ ............ ............ ..........30 Plants from a cluster of fibrous roots, without rhizomes or hard knotty crowns, annual
............ ............ ............ ............ ..........30 Plants with rhizomes or hard knotty crowns, perennial.
............ ............ ............ ............ ............ 31 Plants with hard crowns, lacking rhizomes; fertile lemma 1.2-1.6 mm long
............ ............ ............ ............ ............ 31 Plants with rhizomes; fertile lemma 1.6-4 mm long.
............ ............ ............ ............ ............ ..32 Rhizomes about 1 cm thick with pubescent scale-like leaves; lower portion of culm hard, nearly woody
............ ............ ............ ............ ............ ..32 Rhizomes less than 1 cm thick with glabrous scale-like leaves; culms not woody.
............ ............ ............ ............ ............ ....33 First glume truncate apically
............ ............ ............ ............ ............ ....33 First glume acute to obtuse.
............ ............ ............ ............ ............ ......34 Culms slightly compressed below; ligules 0.5 mm long or less; spikelet pedicels appressed, the spikelets subsecund, usually some obliquely bent above the first glume; fertile lemma 1.8-2.2 mm long
............ ............ ............ ............ ............ ......34 Culms terete; ligules 1-6 mm long; at least some spikelet pedicels spreading, spikelets not at all secund, essentially straight; fertile lemma 2-4 mm long