Poa palustris
Fowl Bluegrass

Spikelet, Two Views

Trout Pond East of Hudson Bay

Note the glumes are straight, not sickle-shaped, and they posses a keel.  The tip of the lower glume is sharp-pointed, much narrower than the tip of the lowest lemma, and usually does not reach the tip of the lowest lemma.  Note the keel on the lemma.

The following items are taken from keys in Flora of Saskatchewan, Fascicle 4, Grasses of Saskatchewan by Anna L. Leighton and Vernon L. Harms.  Family Poaceae is first divided into tribes, then the tribes are divided into genera, and the genera divided into species.  However, there are a number of tribes that are very difficult to distinguish morphologically.  These are grouped into a large, artificial tribe I call "Multitribe".  Multitribe is then divided into groups, and each group is then divided into genera.  The answers are the the order you would normally work through the keys.

Multitribe: Answers to key questions leading to this tribe. 
Mature inflorescence, if breaking into units, then the units not as below; NOT [Mature inflorescence breaking into spikelet units consisting of a sessile fertile spikelet, a hairy pedicel with or without a sterile spikelet at tip, and a hairy rachis joint, all arising at the same point (a node) in specialized panicle branches called rames]
Spikelets not as below; sterile florets if present, either located distal to the fertile floret(s) on the rachilla or paired and attached at the base of a single fertile floret, not paired with the upper glume as below; lemma and palea variously textured, enclosing the flower or not; disarticulation usually above the glumes; NOT [Spikelets usually dorsally compressed, appearing 1-flowered but containing 1 fertile floret and 1 sterile floret, the latter attached to the base of fertile floret opposite the upper glume, resembling the upper glume, and together with the upper glume enveloping the fertile floret; lower glumes minute (sometimes absent) to 3/4 as long as upper glumes and typically wrapping most of the way around the pedicel at base; fertile floret seed-like with chartaceous-indurate lemma and palea enclosing flower and fruit; disarticulation below the glumes with rare exceptions]
Spikelets 1 to many-flowered, subtended by a pair of glumes (only 1 on lateral spikelets in Lolium); palea margins enclosed or not; plants of dry or wet habitats; NOT [Spikelets 1-flowered, lacking glumes; margins of the palea tightly enclosed by the lemma margins on female or perfect florets; plants of wetlands, often emergent aquatic]
Inflorescence not as below; if a terminal spike, then the lateral spikelets attached edgewise to the rachis with inner (upper) glume wanting (as in Lolium); NOT [Inflorescence a terminal spike with sessile or subsessile spikelets attached broadside at nodes on opposite sides of the rachis]
Lemmas and lemma awns not as below; if lemma indurate and enveloping the floret, then glumes distinctly dorsally compressed and calluses glabrous (as in Milium); NOT [Lemmas stiff to indurate, firmer than the glumes, surrounding the palea and often overlapping along the margins, closed at the tip as well as at the base, often pubescent; lemma awns (caducous or wanting in some species) terete and encircled at the base by the closed tip of the lemma; calluses usually pubescent, rarely glabrous]

Group3: Answers to key questions leading to this group. 
If plants mat-forming, then inflorescences not as below; NOT [Mat-forming annuals or perennials either with clusters of spikelets hidden by sharp-pointed leaves at branch tips, or with pistillate inflorescences consisting of burs partially hidden within expanded leaf sheaths with only the staminate inflorescences exceeding the upper leaves]
Inflorescence not as below, the spikelets usually on pedicels in panicles that range from spike-like to open; if spikelets sessile, then they either have more than 1 fertile floret per spikelet or are not arranged like the teeth of a comb; NOT [Inflorescence consisting of spike-like panicle branches with sessile- subsessile, closely imbricate, regularly-spaced, parallel spikelets all directed toward 1 side of the branch like the teeth of a comb (loosely so in Bouteloua curtipendula); fertile florets 1 per spikelet]
Spikelets with more than 1 fertile floret; sterile florets if present, attached above the fertile florets (Phragmites, with sterile florets attached above and below fertile florets, is an exception); NOT [Spikelets with 1 fertile floret; sterile florets if present, attached above or below the fertile floret]

Poa: Answers to key questions leading to this genus. 
Inflorescence a panicle with all spikelets subtended by 2 glumes; NOT [Inflorescence a terminal spike; lateral spikelets positioned edgewise to the rachis and lacking a glume on inside edge]
Spikelets usually pedicellate; if sessile-subsessile, then not arranged as below; NOT [Spikelets sessile or subsessile on spike-like panicle branches, or on short secondary branches in dense one-sided clusters at branch tips]
Rachillas glabrous or pubescent; if pubescent, then hairs much shorter than the lemmas; panicles and plants not as below; NOT [Rachillas with silky hairs (4) 6-10 mm long, as long as the lemmas or nearly so; panicles 15-35 (45) cm long, 8-20 cm wide at maturity, dense, feathery; plants 10-30 (40) dm tall, with stout, creeping rhizomes and often forming dense stands]
Glumes < 17 mm long; if glumes longer, then plants perennial; NOT [Glumes 18-32 mm long, usually exceeding the lemmas; plants annual]
Plants without the below combination of characteristics; NOT [Culm sheaths closed to near summit; leaf blades flat; spikelets 12-40 (55) mm long; lemmas 7-14 (21) mm long, usually awned, the awns terminal or subterminal; calluses glabrous; ovaries and caryopses with pubescent apical appendage; caryopses adnate to paleas at maturity]
Plants without the below combination of characteristics; NOT [Rachilla conspicuously pubescent with straight hairs; calluses bearded; spikelet 2 (3-4) flowered; lemma 2-4 toothed, sometimes obscurely so, sometimes entire; lemma awns attached dorsally or just below apex, often exceeding the lemma apex by only 1-2 mm (awn may be absent in Trisetum wolfii)]
Lemmas unawned or awned; if awns present, then the awns straight and terminal or subterminal, and the calluses glabrous or with short, sparse hairs; NOT [Lemmas awned, the awns 3-17 mm long, slightly outcurving or geniculate, attached dorsally about midlength, or at base of 0.5-8 mm long apical teeth; calluses with dense or long hairs]
Lemmas with 5 - 11 visibly-raised nerves or nerves too obscure to count; NOT [Lemmas with 3 visibly-raised nerves (1 midnerve and 2 lateral nerves)]
Lemmas not as below, either keeled, or with obscure nerves or nerves converging distally; calluses glabrous or pubescent; NOT [Lemmas rounded or weakly keeled on the back, with 5-11 visibly- raised nerves that are +/- parallel their full length, their tips not converging distally; calluses glabrous]
Plants not as below; NOT [Plants low (to 4 (6) dm high), halophytic, dioecious perennials with scaly, stout, creeping, much-branched rhizomes; leaf blades strongly 2-ranked, 1-12 (20) cm long, reaching or exceeding at least the panicles; lemmas of flowers coriaceous, closely imbricate; caryopses long-beaked, the dark tip often visible between the pale-colored lemma and palea]
Plants growing in dry or wet habitats but not typically in water; rhizomes present or absent; culms slender and not particularly spongy at base; other features various; NOT [Plants growing in shallow water or wetlands; rhizomes extensive, creeping, thick, soft, succulent; culms thick (6 - 8 mm wide) and spongy at base; leaf sheaths open, large, papery, +/- inflated, the lower sheaths often cross-septate with air chambers; calluses densely bearded; lemma unawned but sometimes with nerves excurrent at tip]
Glumes not as below; disarticulation above the glumes; other features various;  NOT [Upper and lower glumes markedly dissimilar in shape, the lower glume subulate to linear and less than 1/3 as wide as the upper; the upper glume oblanceolate to obovate, and about 1/2 as wide to nearly as wide as long; spikelets 2-4 mm long, 2-3-flowered; disarticulation below the glumes with the distal floret sometimes falling before the spikelet]
Spikelets (1) 2-11 (15)-flowered; upper glume length various but if reaching the tip of the distal lemma, then glumes (6) 7-8.5 (9.5) mm long; rachises and panicle branches scabrous on the angles or smooth but not pubescent; sheaths open or closed part way; NOT [Spikelets (1) 2-3 (4)-flowered; upper glume as long as the lowest lemma and sometimes reaching the tip of the distal lemma, 3-4 (5.5) mm long; rachises and panicle branches densely puberulent to villose; sheath open to base]
Lemmas lacking mucros or awns; glumes distinctly shorter than the lemmas, and plants lacking auricles; NOT [Lemmas mucronate or awned from the tip except sometimes lacking awns and mucros in plants with glumes reaching the tip of the distal lemma and in plants with soft auricles present on leaves at base of plant]
Lemmas usually keeled, sometimes rounded on the back; if rounded, then lemmas >= 3.5 mm long; lemma tips entire; calluses either glabrous or pubescent with curly or pleated hairs (a web) or with dense straight hairs (a crown); NOT [Lemmas rounded on back, 1.5-3 mm long; lemma tips finely erose; calluses with a few short hairs of irregular lengths]

Palustris: Answers to key questions leading to this species
Plants perennial and found in various habitats, tufted or not; culm height various but often > 2 dm; mature caryopses slender their full length, leaving paleas enclosed within the lemma margins; well-developed anthers (0.8) 1-3.5 mm long; other factors various; NOT [Plants annual, typically found in human-disturbed habitats, densely tufted, often spreading by basal branching and forming mats; culms usually < 2 dm high at maturity; leaf blades soft, thin, broad-tipped, often transversely wrinkled for short sections; panicles to 7 (10) cm long, pyramidal in shape; mature caryopses plump ventrally, pushing paleas into full view; palea keels usually short- to long-villous, rarely glabrous; calluses glabrous; well-developed anthers only to 1.1 mm long]
Culms and leaf sheaths terete or somewhat flattened distally but not sharply edged; culm nodes terete; rhizomes present or absent; some or most leaves basal; other features various; NOT [Culms and leaf sheaths markedly compressed and +/- sharply 2-edged distally; culm nodes compressed; extensive rhizomes present; leaves mostly cauline; sheaths usually shorter than internodes, exposing lower culm nodes; most panicle branches bearing spikelets to near base; lemmas coriaceous-membranous, often muriculate, glabrous except for short-villous lower keel and marginal nerves; calluses usually +/- webbed, sometimes glabrous]
Plants usually tufted; if rhizomes present, then calluses glabrous or sparsely webbed with hairs < 1/4 lemma length and plants restricted to s SK; lemma keel and marginal nerve pubescence various; NOT [Plants with well-developed rhizomes and copiously webbed calluses, the callus hairs over 1/2 the length of the lemma (occasionally sparsely webbed with shorter hairs in P. arctica subsp. arctica, a rare plant restricted to the far north); lemma keels and marginal nerves long-villose]
Plants growing in Aspen Parkland, Mixed-grass Prairie and Cypress Hills regions; NOT [Plants growing in the boreal forest region and/or Subarctic Transitional Forest]
Tip of lower glume sharp-pointed and much narrower than tip of lowest lemma; lemmas 2-3 (3.5) mm long; spikelets (2.6) 3-5 (5.5) mm long; plants loosely to densely tufted; rhizomes absent, stolons sometimes present; callus webs usually present, ranging from minute to long (over 2/3 lemma length); panicles narrowly lanceolate, ovate, elliptic or pyramidal; NOT [Tip of lower glume acute and only slightly narrower than tip of lowest lemma; lemmas 2.5-7 mm long; spikelets 3.2-7 mm long; plants solitary to densely tufted, rhizomes present or absent, stolons absent; callus webs absent or short (less than 1/4 lemma length); panicles narrowly lanceolate to ovate]
Plants loosely to densely tufted, often stoloniferous; culms often decumbent or geniculate at base and sometimes rooting at lower nodes; panicles (8) 10-25 (30) cm long, 2-3 times longer than wide, oblong, elliptic or pyramidal; lower branches initially erect becoming spreading to slightly reflexed, 2-9 at lower nodes; ligules on main culms up to or longer than 3 mm long, acute, acuminate or obtuse; calluses sparsely to +/- densely webbed, the hairs 1/2 to over 2/3 lemma length; plants usually of moister habitats such as marshes, moist-wet meadows, damp open woods and shores; NOT  [Plants usually densely tufted, not stoloniferous; culms usually erect, not decumbent at base or rooting at lower nodes; panicles (1.5) 3-15 (17) cm long, 2.5-4 times longer than wide, narrowly lanceolate to narrowly ovate or narrowly pyramidal; lower branches ascending, occasionally spreading, 2-5 at lower nodes; ligules on main culms usually < 1.5 mm long, obtuse to truncate; calluses usually webbed but the hairs few, usually < 1/2 lemma length, sometimes minute; plants of dry-mesic, semi-open forests and prairie hillsides and plains]
Lemma lateral nerves obscure and the keel short villous; lower panicle branches 4-15 cm long; sheaths closed for about 1/4 their length; calluses sparsely to densely webbed with hairs to over > 1/2 the lemma length; lower glumes tapering to apex; ligules on main culms to 5 (6) mm long, acute to obtuse; leaf blades (1) 1.5-2 (4) mm wide; plants widespread across SK; NOT [Lemma lateral nerves pronounced and the keel usually sparsely puberulent for up to 2/3 lemma length; primary panicle branches 2-8 (10) cm long; sheaths closed about 1/3 to 1/2 their length; calluses strongly webbed with hairs > 2/3 lemma length; lower glumes usually arched to sickle-shaped; ligules to 8 (10) mm long, acute to acuminate; leaf blades 1-5 mm wide; 1 SK record]