Key 1. Key to some unusual grasses and to subsequent keys

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Bisexual or pistillate spikelets encased in a spiny bur, aggregated into a hard bur-like cluster, or embedded in a cob surrounded by a leafy husk 2

• 1b.Spikelets in inflorescences exserted above the leaf sheaths, or in a few grasses partially or completely enclosed within a leaf sheath, but not encased in a bur or a husk of many leaves 4

• 2a.Pistillate spikelets ("kernels") in two or more rows sunken in a thickened cob, surrounded by a leafy husk; apex of stem topped with racemes ("tassels") of staminate flowers Zea

• 2b.Spikelets encased in spiny burs or aggregated into a hard bur-like cluster 3

• 3a.Spikelets bisexual, each spikelet encased in a spiny bur formed by coalesced bristles; plants annual, without stolons Cenchrus (in part)

• 3b.Spikelets pistillate, 4 or 5 in a head, aggregated into a globular cluster surrounded by hardened glumes; stoloniferous perennials Bouteluoa (in part)

• 4a.Inflorescences with two distinctly different spikelets: one bisexual or pistillate, the other staminate or sterile 5

• 4b.Inflorescences with all spikelets alike 11

• 5a.Inflorescence a panicle of two parts: pistillate spikelets with long awns, on erect or ascending branches in the upper part; and awnless staminate spikelets pendent on spreading branches in the lower part of the panicle Zizania

• 5b.Inflorescence a uniform panicle, spike, or rame, with bisexual, pistillate, staminate, or sterile spikelets distributed throughout the inflorescence 6

• 6a.Fertile spikelets with 2 or 3 florets, nearly hidden by more numerous sterile spikelets consisting of many empty narrow lemmas Cynosurus

• 6b.Fertile spikelets with one fertile floret; sterile or staminate spikelets not covering fertile spikelets 7

• 7a.Fertile spikelets sessile at each rachis node of a spike, between two sterile or rudimentary spikelets each on a short pedicel Hordeum

• 7b.Fertile spikelets sessile at each node of a rame (a raceme-spike combination), each accompanied by a smaller pedicelled staminate or rudimentary spikelet 8

• 8a.Inflorescence a panicle of many short rames 9

• 8b.Inflorescences of one to several long rames 10

• 9a.Pedicelled spikelet sterile or staminate; ligule of soft hairs Sorghum

• 9b.Pedicelled spikelet usually absent, rarely rudimentary; ligule stiff and cartilaginous Sorghastrum

• 10a.Rames 2--6 in digitate groups; pedicelled spikelets staminate Andropogon

• 10b.Rames solitary at the ends of peduncles, pedicelled spikelets reduced, and sterile Schizachyrium

• 11a.Spikelets subtended (surrounded at the base) by bristles longer than the spikelets 12

• 11b.Spikelets not subtended by stiff bristles, although glumes or florets may have bristle-like awns or soft hairs 13

• 12a.Bristles less than 2 cm long, persisting after spikelets drop Setaria

• 12b.Bristles 2--4 cm long, falling attached to the spikelets Cenchrus (in part)

• 13a.Culms more than 2 m tall Key 2

• 13b.Culms normally less than 2 m tall, or specimen incomplete, height unknown 14

• 14a.Leaf sheaths closed (margins fused for more than 1 cm above the node) Key 3

• 14b.Leaf sheaths open (margins overlapping their entire length or fused only at the base), or specimen lacking leaf sheathes 15

• 15a.Spikelets consisting of only one floret, without any glumes Leersia

• 15b.Spikelets with one or two glumes at base; florets one or more 16

• 16a.Inflorescence a spike, a dense spike-like panicle, or consisting of short spikes or spike-like branches attached to the inflorescence axis; not an open panicle; pedicels shorter than the spikelets 17

• 16b.Inflorescence an open panicle (usually with major branches spreading at anthesis), the main branches rebranching and longer than the spikelets 19

• 17a.Inflorescence of spikes, racemes, or rames radiating more-or less digitately from at or near the top of the inflorescence axis (peduncle) or attached pinnately along the inflorescence axis Key 4

• 17b.Inflorescence a single unbranched spike with all spikelets sessile along the inflorescence axis, or a very dense cylindrical spike-like panicle or raceme with branches and pedicels shorter than the spikelets 18

• 18a.Inflorescence a single spike with all spikelets attached directly to the main axis Key 5

• 18b.Inflorescence a dense cylindrical spike-like panicle or raceme with branches and pedicels shorter than the spikelets Key 6

• 19a.Spikelets with conspicuous awns Key 7

• 19b.Spikelets without conspicuous awns (including some species with inconspicuous minute awns about 1 mm long, or short awns concealed by the glumes) 20

• 20a.Spikelets with only one conspicuous bisexual floret (plus some species with reduced, sterile, or rudimentary florets covered by the glumes) Key 7

• 20b.Spikelets with two or more fertile florets Key 10

• 21a.Mature fertile floret thick and usually rigid, subtended by thin broadly rounded or dorsally compressed glumes (including most species with panicoid spikelets) Key 8

• 21b.Mature floret thin and flexible, with the same texture as the laterally compressed, folded, or keeled glumes (including species with additional staminate, sterile, or rudimentary florets) Key 9

Key 2. Grasses more than 2m tall

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Inflorescence of several short lateral one-sided spikes arranged pinnately along one side of the main axis Spartina

• 1b.Inflorescence a panicle or a cluster of several racemes or rames 2

• 2a.Inflorescence a panicle with all spikelets pedicelled and alike 3

• 2b.Inflorescence of racemes or rames with some spikelets sessile; or a complex panicle of bisexual and staminate spikelets, some sessile, some pedicelled 7

• 3a.Upper panicle branches erect or ascending, bearing elongated, awned, terete pistillate spikelets; lower panicle branches spreading, bearing staminate spikelets; all spikelets lacking glumes Zizania

• 3b.All panicle branches alike, ascending or spreading, bearing bisexual spikelets; glumes present on all spikelets 4

• 4a.Spikelets with 2--several florets; perennials with vigorous rhizomes 5

• 4b.Spikelets with 1--2 florets; annuals or clump-forming perennials 6

• 5a.Spikelets at maturity with long silky hairs on the rachilla; glumes and lemmas 3-nerved Phragmites

• 5b.Spikelets lacking silky hairs; glumes one nerved; lemmas with 5--7 raised parallel nerves Glyceria (in part)

• 6a.Spikelets of two fertile florets, lower floret staminate bearing a bent awn near the base, the upper floret bisexual, bearing a short, straight awn; clump-forming perennials Arrhenatherum

• 6b.Spikelets panicoid, with one bisexual floret, plus a sterile vestigial floret represented by a lemma resembling the second glume; all florets awnless; annuals or rhizomatous perennials Panicum (in part)

• 7a.Inflorescence a large group of many long racemes of all bisexual or all staminate spikelets 8

• 7b.Inflorescence of short rames consisting of sessile bisexual spikelets and pedicelled staminate spikelets 9

• 8a.Inflorescence a "tassel" of many elongated racemes of staminate spikelets Zea

• 8b.Inflorescence a digitate cluster of several racemes of pedicelled bisexual spikelets Miscanthus

• 9a.Rames long, of more than 20 spikelets each, 2--6 in a digitate cluster on a peduncle Andropogon

• 9b.Rames short, of a few spikelets each, forming a large, complex panicle 10

• 10a.Pedicelled spikelets staminate or sterile; ligule of soft hairs Sorghum

• 10b.Pedicelled spikelets absent or rudimentary; ligule stiff and cartilaginous Sorghastrum

Key 3. Grasses with closed leaf sheaths
(fused for more than 1cm above the node)

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Spikelets with 2 florets; lemmas with 3 nerves Catabrosa

• 1b.Spikelets with 3--6 florets; lemmas with 5--7 nerves 2

• 2a.Spikelets in glomerules (small dense clusters) at the ends of a few stiff, elongated panicle branches Dactylis

• 2b.Spikelets evenly dispersed throughout the panicle 3

• 3a.Lemmas awnless 4

• 3b.Lemmas awned 6

• 4a.Lemmas with nerves converging toward the apex; leaf blades with an M-shaped crease about midway between the base and the apex Bromus (in part)

• 4b.Lemmas with nerves parallel and often raised, not converging toward the apex; leaf blades without an M-shaped crease 5

• 5a.Lemmas all similar in shape; glumes one-nerved Glyceria

• 5b.Uppermost lemma convolute (inrolled), club-shaped; glumes 3--5 nerved Melica (in part)

• 6a.Lemmas awned from the middle of the back; rachilla densely hairy Avenula

• 6b.Lemmas awned from near the apex; rachilla glabrous or puberulent 7

• 7a.Callus of floret bearded; glumes purplish; lemmas green Schizachne

• 7b.Callus of floret glabrous; glumes and lemmas uniformly green or purplish 8

• 8a.Leaf sheaths retrorsely scabrous; lemmas 7-nerved Melica (in part)

• 8b.Leaf sheaths glabrous, or pubescent, but not retrorsely scabrous; lemmas 5--7 nerved Bromus (in part)

Key 4. Inflorescence of two or more spikes, racemes/rames, or densely flowered spike-like branches arising directly from the inflorescence axis

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.All or most spikes, racemes/rames, or spike-like branches radiating digitately (palmately) from at or close to the tip of the inflorescence axis, some species with solitary spikes or additional whorls of spikes below 2

• 1b.Spikes, racemes/rames, or spike-like branches attached singly (pinnately) along the inflorescence axis (only a single lateral spike present in some Bouteloua specimens) 7

• 2a.Plants erect, 1--3 m tall; spikelets 7--10 mm long, sessile or pedicelled 3

• 2b.Plants sprawling, creeping, or erect, less than 1 m tall; spikelets less than 7 mm long, sessile along one side of spikes 4

• 3a.Racemes/rames 5--20, covered by long silky-white hairs, not disarticulating at maturity Miscanthus

• 3b.Racemes/rames 2--6, not covered by silky-white hairs, disarticulating at maturity Andropogon

• 4a.Spikelets with 3--6 bisexual florets Eleusine

• 4b.Spikelets with one bisexual floret, with or without an awned rudimentary sterile floret 5

• 5a.Annuals; spikelets panicoid; first glume absent, or less than 0.4 mm long, second glume and sterile lemma thin and flat; upper floret bisexual, thick, and leathery Digitaria (in part)

• 5b.Perennials; spikelets not panicoid; both glumes present, 2--4 mm long, lower floret bisexual, thin; upper floret rudimentary, sterile, or lacking 6

• 6a.Spikes in 2--few separate whorls; lemmas with awns about 2 cm long; upper floret sterile Chloris

• 6b.Spikes in a single whorl; lemmas lacking conspicuous awns; upper floret lacking Cynodon

• 7a.Spikelets well-separated and appressed on all sides of branches, with five to many florets; plants sprawling Schizachne

• 7b.Spikelets tightly-packed, in most species confined to one side of the rachis; spikelets with one or two florets; plants usually erect 8

• 8a.Spikelets laterally compressed, glumes and lemmas folded lengthwise, keeled 9

• 8b.Spikelets terete to dorsally flattened, the glumes and lemmas broadly rounded 11

• 9a.Spikelets with one bisexual floret, lacking rudimentary florets; plants with rhizomes 10

• 9b.Spikelets with two or more florets including rudimentary florets; plants less than 1 m tall, with stolons or short rhizomes Bouteloua

• 10a.Spikelets 4--8 mm long, in dense clusters on all sides of short ascending branches; plants up to 1 m tall; rhizomes 2--4 mm thick Muhlenbergia (in part)

• 10b.Spikelets 12--16 mm long, densely packed along one side of many spike branches; rhizomes 4--8 mm thick; plants 1--2 m tall Spartina

• 11a.Spikelets awned 12

• 11b.Spikelets awnless 13

• 12a.Inflorescence a pyramidal panicle of thick racemes; spikelets panicoid Echinochloa

• 12b.Inflorescence an elongate aggregation of solitary racemes/rames on peduncles; spikelets narrowly linear, lanceolate, scabrous Schizachyrium

• 13a.Spikelets flattened, suborbicular; glumes equal, deeply pouch-like, covering the single floret Beckmannia

• 13b.Spikelets panicoid, ovate or plano-convex, first glume minute or absent 14

• 14a.Spikelets broadly ovate, apex acute, with a cup-like disk at the base; rachis villous Eriochloa

• 14b.Spikelet plano-convex, orbicular, apex round; base rounded without a cup-like disk; rachis glabrous Paspalum

Key 5. Inflorescence a single true spike, with all spikelets attached directly to the main axis

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Lemmas strongly laterally compressed, strongly keeled, keels lined with stout recurved spine-like bristles about 1 mm long Secale

• 1b.Lemmas not strongly compressed and keels, keels without recurved bristles 2

• 2a.Spikelets attached to the rachis (main axis) with narrow edge against the rachis; the first glume absent from all but the terminal spikelet, the second glume longer than a lemma, on the edge away from the rachis Lolium (in part)

• 2b.Spikelets attached with the wide, flat side against the rachis; both glumes of each spikelet alike 3

• 3a.Most nodes of the rachis with two to four spikelets 4

• 3b.All or most nodes with only one spikelet 6

• 4a.Each node with three spikelets, each spikelet with two awned glumes, the central spikelet sessile and bisexual, the two lateral spikelets sessile, or on short pedicels, and rudimentary; awns on lemma of bisexual spikelets larger and thicker than awns on glumes; annuals or perennials Hordeum

• 4b.Most nodes with two spikelets (rarely three or four), all sessile and alike, each with two or more florets; awns of uniform thickness, or awns absent; plants perennial 5

• 5a.Lemmas awned, awns usually 1--10 cm long; glumes glabrous or minutely scabrous, or glumes absent; blades well-spaced on culms, upper surface with numerous unequally prominent veins Elymus (in part)

• 5b.Lemmas awnless (or minutely awned); glumes at least partly pubescent; blades stiff, crowded near base of culms, upper surface glaucous with 15—30 similar prominent veins Leymus

• 6a.Glumes coriaceous, 3--7 mm wide, about twice as long, with three to nine nerves; mature spikes about 2 cm wide; annuals Triticum

• 6b.Glumes thin, less than 3 mm wide, more than three times as long, with one to five nerves; mature spikes about 1 cm wide; perennials 7

• 7a.Lemmas densely hairy or with long awns recurving at maturity Elymus (in part)

• 7b.Lemmas glabrous , lacking long recurving awns 8

• 8a.Spikelets closely packed and spreading from rachis at more than a 45o angle; midrib of glumes asymmetric and strongly keeled Agropyron

• 8b.Spikelets not tightly packed, ascending to spreading; midrib of glume symmetrical, not strongly keeled 9

• 9a.Glumes linear-lanceolate, tapering from below the middle to acuminate apices; margin minutely ciliate; leaves bluish-glaucous, often involute, the upper surface with 7--14 raised nerves Pascopyrum

• 9b.Spikelets with two or more florets including rudimentary florets; plants less than 1 m tall, with stolons or short rhizomes Elymus (in part)

Key 6. Inflorescence a single dense, spikelike panicle

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Spikelets unisexual, plants dioecious, staminate and pistillate plants similar; leaf blades strongly distichous, involute, ascending; spikelets many flowered Distichilis

• 1b.Spikelets bisexual and alike; leaf blades not stiff, not strongly distichous 2

• 2a.Spikelets awnless or awn inconspicuous, "hidden" among long callus hairs 3

• 2b.Spikelets awned or subtended by bristles 1--2 mm long 9

• 3a.Inflorescence 1--4 cm long, partly included in leaf sheath; low tufted annuals 4

• 3b.Inflorescence more than 4 cm long, usually exserted well above the leaf sheath; erect perennials 5

• 4a.Spikelets with three florets, the uppermost sterile; glumes broad, obtuse, hard; lemmas thick, rounded on the back, obtuse, with five prominent raised parallel nerves; ligule membranous Sclerochloa

• 4b.Spikelet with one floret; glumes narrow, acute, thin; lemma membranous, acute, with one nerve; ligule hairy Sporobolus (in part)

• 5a.Spikelets with one fertile floret 6

• 5b.Spikelets with two florets, callus without hairs; plants less than 50 cm tall 8

• 6a.Inflorescence an ovoid spike, glumes broadly boat-shaped with wide winged keel; spikelets with one fertile floret plus two empty lemmas; annuals Phalaris (in part)

• 6b.Inflorescence an elongated spike; glumes not wide winged; spikelets without additional empty lemmas; perennials 7

• 7a.Spikelets 10--15 mm long; leaf blades stiffly involute; stout plants with vigorous rhizomes Ammophila

• 7b.Spikelets 3--5 mm long, with an inconspicuous awn among the callus hairs; leaf blades thin, and normally flat; rhizomes slender Calamagrostis (in part)

• 8a.Peduncle finely pubescent below the inflorescence; spikelets dull; larger glumes 3--4.7 mm long; florets disarticulating above the glumes Koeleria

• 8b.Peduncle glabrous; glumes less than 3.2 mm long; spikelets shiny, disarticulating below the glumes Sphenopholis

• 9a.Spikelets panicoid, not awned, subtended by one to twelve bristles Setaria

• 9b.Spikelets not panicoid, awned, not subtended by bristles 10

• 10a.Spikelets with two or more florets 11

• 10b.Spikelets with one floret 13

• 11a.Spikelets with two similar bisexual florets, awns 3--5 mm long Trisetum

• 11b.Spikelets of more than two dissimilar florets, some staminate or sterile, awns less than 3 mm long 12

• 12a.Spikelets in fascicles, the terminal spikelet terete, sessile, with two or three bisexual florets, partly covered by flat sterile spikelets consisting of many narrow, awned, empty florets Cynosurus

• 12b.Spikelets alike, each with one central bisexual floret and two awned sterile florets Anthoxanthum (in part)

• 13a.Glumes broadly rounded; florets 5--7 mm long, hard, shiny, dark brown at maturity, with a woolly base and a deciduous awn; leaves evergreen, mostly basal Oryzopsis

• 13b.Glumes narrow or folded and keeled, florets 1--6 mm long, not hard or shiny; leaves not evergreen, mostly cauline 14

• 14a.Glumes awnless; lemma with an inconspicuous awn attached near base of the keel Alopecurus

• 14b.Glumes awned, lemma awnless or with a minute awn at the tip 15

• 15a.Glumes folded with a ciliate keel, truncate at apex, with abrupt awn 1--2 mm long; perennials from a bulblike base Phleum

• 15b.Glumes somewhat folded, without a ciliate keel, and not truncate at apex; annuals or perennials, without a bulblike base 16

• 16a.Glumes 2--3 mm long, excluding the awns; awns threadlike, 2--10 mm long, dense, making the panicle appear silky; annuals or perennials Polypogon

• 16b.Glumes narrowly linear-lanceolate tapering to awns, 4--8 mm long; rhizomatous perennials Muhlenbergia (in part)

Key 7. Inflorescence an open panicle; spikelets with conspicuous awns

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Glumes 18--25 mm long Avena

• 1b.Glumes less than 15 mm long 2

• 2a.Awns three-forked Aristida

• 2b.Awns unbranched, one per spikelet 3

• 3a.Glumes hard; lemmas thin and translucent; bisexual spikelets sessile in short racemes/rames, paired with one or two staminate or sterile spikelets, or a ciliate pedicel 4

• 3b.Glumes thin, soft; lemmas rigid or thin but not translucent; spikelets pedicelled 5

• 4a.Pedicelled spikelet staminate or sterile; ligule of soft hairs Sorghum

• 4b.Pedicelled spikelet usually absent, the pedicel ciliate; ligule stiff and cartilaginous Sorghastrum

• 5a.Spikelets with a single fertile floret 6

• 5b.Spikelets with two or more fertile florets 17

• 6a.Floret thin, more-or-less membranous, not harder than the glumes, dull, usually laterally compressed; awn not jointed at the base 7

• 6b.Floret rigid, harder than the glumes, usually shiny, terete, or dorsally compressed; awn persistent or deciduous, jointed at base in some species 12

• 7a.Spikelets unisexual; pistillate spikelets awned, elogate, terete, on erect to ascending branches in the upper part of the panicle; staminate flowers pendent, awnless, on spreading lower branches; tall, pulpy annuals Zizania

• 7b.Spikelets bisexual and alike; panicle not differentiated into erect and spreading branches 8

• 8a.Lemma surrounded at base by hairs 2--4 mm long, partly concealing a dorsal awn Calamagrostis

• 8b.Lemma glabrous or hairs less than 1 mm long, awn conspicuous, arising near the tip of the lemma or glumes 9

• 9a.Spikelets 8--13 mm long, excluding awns; glumes minute; leaf blades 6--20 mm wide, constricted at base, finely hairy Brachyelytrum

• 9b.Spikelets 2--4 mm long, excluding awns; glumes 2--8 mm long; 1--8 mm wide, not constricted at base, glabrous or scabrous 10

• 10a.Glumes with two tiny terminal teeth and slender awns 2--10 mm long; spikelets falling with the glumes Polypogon

• 10b.Glumes without terminal teeth, tapering to an awn attached to the lemma; florets falling separately, leaving the glumes attached to the panicle branches 11

• 11a.Awn 4--10 mm long, attached below lemma tip; glumes awnless; rachilla prolonged as a bristle beyond the floret base Apera

• 11b.Awn 1--10 mm long, attached to the tip of the lemma or glumes, rachilla not prolonged as a bristle Muhlenbergia

• 12a.Spikelets panicoid, dorsally compressed, usually hispid, with one or two awns; lower floret sterile, with a thin lemma resembling the second glume annuals Echinochloa

• 12b.Spikelets terete to laterally compressed, glabrous, with one abruptly distinct awn, jointed at the tip of a hard, ovoid floret; sterile floret absent; perennials 13

• 13a.Awn persistent, twisted near base, stout 14

• 13b.Awn deciduous, straight, rather delicate 15

• 14a.Awn 10--20 cm long; body of lemma 10--25 mm long Hesperostipa

• 14b.Awn 2--4 cm long; body of lemma 4--7 mm long Nassella

• 15a.Panicle raceme-like; leaves evergreen, mostly basal Oryzopsis

• 15b.Panicle open; leaves deciduous, cauline 16

• 16a.Leaves 1--2 mm wide, dull; lemmas 2.5--4 mm long Piptatheropsis

• 16b.Leaves 8--15 mm wide, shiny; lemmas 5--7 mm long Patis

• 17a.Spikelets with only two florets 18

• 17b.Spikelets with three or more florets 23

• 18a.Spikelets hairy, disarticulating below the glumes; upper floret with a tiny fishhook-shaped awn Holcus

• 18b.Spikelets glabrous (except for hairy callus), disarticulating above the glumes; upper floret awnless, or awn not hook-shaped 19

• 19a.Lemma awns 1.5--2 mm long Deschampsia

• 19b.Lemma awns 3--20 mm long 20

• 20a.Lemmas 8--15 mm long, the awns 15--20 mm long Avenula

• 20b.Lemmas 2--7 mm long, the awns 3--10 mm long 21

• 21a.Lower lemma with prominent bent awn; upper lemma with short, straight awn; robust plants 1--2 m tall Arrhenatherum

• 21b.Both lemmas with prominent awns; plants less than 1 m tall 22

• 22a.Lower lemma with arising from the back near the base; upper lemma with awn less than 8 mm long Avenella

• 22b.Lower lemma with awn arising at the tip; upper lemma with an awn 10--16 mm long Ventenata

• 23a.Glumes 7--14 mm long, exceeding the uppermost florets; summit of leaf sheath with a beard of hairs Danthonia

• 23b.Glumes much shorter than the entire spikelet; leaf sheath lacking a beard of hairs 24

• 24a.Awn arising from the apex of the lemma; leaf sheaths open, margins free 25

• 24b.Awn arising between two teeth at the apex of the lemma; leaf sheath closed, the margins fused 26

• 25a.Lemmas with three minute awns arising from the apex of the lemmas Tridens

• 25b.Lemmas with only one tapering terminal awn Festuca

• 26a.Awn arising from between two large teeth about one-quarter the length of the lemma; glumes purple, florets green Schizachne

• 26b.Awn arising from between two small teeth about 1 or 2 mm long, less than one-quarter the length of the lemma; spikelets not bicolored, either all purple or all green 27

• 27a.Leaf sheaths retrorsely scabrous; ligules 2--7 mm long; lemmas seven-nerved Melica (in part)

• 27b.Leaf sheaths glabrous or pubescent, not retrorsely scabrous; ligules usually less than 3 mm long; lemmas five-nerved Bromus

Key 8. Inflorescence an open panicle, spikelets lacking conspicuous awns at maturity, with one bisexual floret thick and usually hard at maturity, subtended by thin glumes and in some species a "sterile lemma" (includes species with panicoid spikelets)

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Spikelets, including fertile floret, laterally compressed, with two small hairy scales at the base of the bisexual floret Phalaris

• 1b.Spikelets terete or dorsally compressed, with either one thin sterile lemma or none at the base of the fertile floret 2

• 2a.Spikelets terete to narrowly ovoid, pointed; glumes two, membranous, subequal, slightly exceeding the floret; floret forming a hard, shiny grain, the margins of the lemma rolled over the similar palea, resembling a panicoid spikelet but lacking a glume-like "sterile lemma" 3

• 2b.Spikelets panicoid, dorsally compressed, more-or-less elliptical, blunt; glumes two, thin, unequal, the first glume small or absent, the second glume usually matched by an empty "sterile lemma"; fertile floret usually thick, firm, and shiny, the lemma partly rolled over the palea 5

• 3a.Glumes 3.0--3.5 mm long; lemma glabrous, never awned; plants slightly succulent Milium

• 3b.Glumes 4--9 mm long; fruit partly covered with appressed white hairs; young lemma awned, the awn deciduous at maturity 4

• 4a.Inflorescence narrow, with erect or ascending branches; leaves 1--2 mm wide, involute, in a dense cluster; glumes 4--5 mm long Piptatheropsis (in part)

• 4b.Inflorescence wide with most branches spreading, leaves 8--15 mm wide, flat, shiny; glumes 6--9 mm long Patis

• 5a.Spikelets stiffly hispid, subsessile on dense panicle branches Echinochloa (in part)

• 5b.Spikelets glabrous or pubescent, but not hispid or subsessile 6

• 6a.First glume tiny, less than 0.5 mm long; lemma of fertile floret thin, cartilaginous, narrowly elliptic, about three times as long as wide Digitaria (in part)

• 6b.First glume 1--3 mm long; lemma of fertile floret rigid, chartaceous, often shiny, usually less than three times as long as wide 7

• 7a.Lemma apex with a cluster of minute prickles; spikelets dark red-purple; pedicels bearing one to a few delicate hairs about 1 mm long at summit Coleataenia

• 7b.Lemma apex lacking a cluster of minute prickles; spikelets green, tan, or reddish, but not dark purple; pedicels lacking delicate hairs at summit 8

• 8a.Spikelets pubescent Dichanthelium (in part)

• 8b.Spikelets glabrous 9

• 9a.Terminal panicle small, typically less than 10 cm tall and produced before mid-summer, the main branches forked at the base; perennials, usually with a remnant of an overwintering basal rosette of leaves; main culms usually producing dense fascicles of short branches and partly hidden panicles in late summer Dichanthelium (in part)

• 9b.Terminal panicle large, typically 10--40 cm tall, produced in mid-summer into autumn, the main branches not forked at the base; annuals or perennials without overwintering basal rosettes or dense axillary fascicles Panicum

Key 9. Inflorescence an open panicle, spikelets without conspicuous awns, and with one thin bisexual floret (includes species with additional staminate, sterile, or rudimentary florets)

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Spikelets with one fertile bisexual floret plus two larger staminate florets, two sterile florets consisting of small hairy bracts, or a sterile lemma resembling the second glume 2

• 1b.Spikelets with only one bisexual floret 4

• 2a.Spikelet with one tiny glume less than 0.5 mm long, plus a second glume and a matching sterile lemma 2.5--3.5 mm long Digitaria (in part)

• 2b.Spikelets with two equal glumes 4--8 mm long 3

• 3a.Lower two florets staminate, 3--4 mm long; inflorescence a wide, open panicle Anthoxanthum (in part)

• 3b.Lower two florets sterile, reduced to a scale and hairs or a bract, 1--3 mm long; inflorescence dense, ovoid or a thick panicle Phalaris

• 4a.Spikelets consisting of only one flat floret without glumes; palea with three nerves Leersia

• 4b.Spikelets with two glumes; palea with two nerves 5

• 5a.Ligule hairy Sporobolus (in part)

• 5b.Ligule membranous 6

• 6a.Floret raised on a short stalk above the glumes; rachilla prolonged slightly beyond the floret; floret with a minute awn and just one stamen; entire spikelets disarticulating at maturity, taking the glumes with the floret Cinna

• 6b.Floret attached at base of glumes; rachilla not prolonged; floret with three stamens, not dispersing with glumes attached 7

• 7a.Callus or base of lemma with hairs 1--3 mm long, including an inconspicuous awn arising from the back of the lemma Calamagrostis

• 7b.Long hairs absent, or arising in part from the lemma 8

• 8a.Lemma shorter than the glumes, nearly or completely glabrous at base; lemma with five faint veins; lower panicle branches whorled Agrostis

• 8b.Lemma body distinctly longer than the glumes, glabrous to bearded at base; lemma with three conspicuous nerves; panicle branches single at the nodes Muhlenbergia

Key 10. Inforescence an open panicle, the spikelets with two or more fertile florets and no conspicuous awns

Authors: Robert W. Freckmann, John G. Zaborsky, Emmet J. Judziewicz

• 1a.Glumes 18--25 mm long Avena

• 1b.Glumes less than 18 mm long 2

• 2a.Rachilla bearded with long silky hairs; stout reeds with thick culms and large plumose panicles Phragmites

• 2b.Rachilla glabrous or sparsely pubescent; plants not exceptionally large or stout 3

• 3a.Spikelets unisexual, plants dioecious, staminate and pistillate plants similar; leaf blades strongly distichous, involute, ascending Distichlis

• 3b.Spikelets bisexual; leaf blades not notably distichous, involute, and ascending 4

• 4a.Glumes about as-long-as the entire spikelet 5

• 4b.Glumes at least 2 mm shorter than the tip of the spikelet 8

• 5a.Glumes broad and papery, 7--9 mm long Melica (in part)

• 5b.Glumes narrow to obovate, not papery, 2.6--4.7 mm long 6

• 6a.Peduncle finely pubescent below the inflorescence; spikelets dull; larger glumes 3--4.7 mm long; florets disarticulating above the glumes, leaving the glumes behind Koeleria

• 6b.Peduncle glabrous; spikelets disarticulating below the glumes 7

• 7a.Glumes similar, both tapering from base to apex; rachilla villous, prolonged behind upper floret Graphephorum

• 7b.Glumes dissimilar, the first narrow, the second much broader; rachilla prolonged as a slender, glabrous pedicel Sphenopholis

• 8a.Lemmas usually with a tuft of loose cobwebby hairs at base, or culms strongly flattened; leaf blade tips turned up, resembling the prow of a boat or canoe Poa

• 8b.Lemmas lacking a tuft of cobwebby hairs; culms terete; leaf blades tips flat, acute, not boat shaped 9

• 9a.Lemmas with three prominent nerves 10

• 9b.Lemmas with five or more weak nerves 14

• 10a.Lemma nerves hairy; palea densely long-ciliate; mature wiry culms breaking at the nodes Triplasis

• 10b.Lemma nerves glabrous; palea not long ciliate; culms not breaking at the nodes 11

• 11a.Glumes and lemmas stiff, chartaceous; lemmas broad, rigid, shiny; grain large, bottle-shaped, beaked, forcing the lemma and palea apart Diarrhena

• 11b.Glumes and lemmas thin and flexible; grain not notably large or bottle shaped 12

• 12a.Spikelets terete, conical; palea longer than the lemma, bowed out below Molinia

• 12b.Spikelets laterally compressed; palea not longer than the lemma, straight 13

• 13a.Lemma truncate and erose; spikelets with two florets Catabrosa

• 13b.Lemma acute; spikelets with three to many florets Eragrostis

• 14a.Spikelets as-wide-as long, the florets crowded and spreading horizontally; lemmas papery, broad, cordate at base Briza

• 14b.Spikelets longer than wide, the florets not exceptionally crowded or spreading horizontally; lemmas not papery or cordate at base 15

• 15a.Spikelets 2--4 cm long, very flat, the nerves obscure; lemma of the lowest floret empty; panicle top and branches usually drooping Chasmanthium

• 15b.Spikelets less than 2 cm long, not exceptionally flattened; nerves evident; lemmas not empty; inflorescence rarely drooping 16

• 16a.Spikelets strongly compressed, crowded into small dense clusters (glomerules) at the end of a few stiff, elongate inflorescence branches Dactylis

• 16b.Spikelets evenly dispersed throughout a panicle 17

• 17a.Lemma nerves parallel, not (or slightly) converging at the tip 18

• 17b.Lemma nerves converging toward the lemma tip 20

• 18a.Upper glume with one distinct nerve Glyceria

• 18b.Upper glume with three to five distinct nerves 19

• 19a.Lemmas with five faint nerves, minutely hairy at the base; grain usually adherent to the palea Puccinellia

• 19b.Lemmas with seven to nine prominent glabrous nerves Torreyochloa

• 20a.Lemma apex split into two minute teeth Bromus (in part)

• 20b.Lemma apex not split at the tip 21

• 21a.Leaf blades flat, 3--8 mm wide Lolium (in part)

• 21b.Leaf blades involute, less than 3 mm wide Festuca