Elymus repens
 
Quack Grass

Single Shoot

Regina
28-June-2021

Note the presence of a relatively thick rhizome.

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 in the order you would normally work through the keys.

Triticeae: 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 a terminal spike with sessile or subsessile spikelets attached broadside at nodes on opposite sides of the rachis; NOT [Inflorescence not as above; if a terminal spike, then the lateral spikelets attached edgewise to the rachis with inner (upper) glume wanting (as in Lolium)]

Elymus: Answers to key questions leading to this genus. Not all the answers apply to all members of Elymus, but they all do apply to a subset containing E. repens).
Spikelets 1 per node, occasionally 2 at some nodes; NOT  [Spikelets 2 or more per node, occasionally 1 at some nodes]
Spikes not pectinate with spikelets not arranged as below; spikelets usually appressed to ascending, sometimes somewhat divergent; glumes usually flat at base, sometimes keeled towards tip; NOT [Spikes usually pectinate with spikelets closely-set, regularly-spaced and parallel like the teeth of a comb; spikelets divergent at angles of 30 to 90 from the rachis at maturity; glume keels prominent to base]
Introduced or native perennials;  NOT [Introduced annuals rarely found outside cultivation or plantings]
Glumes and lemmas not particularly thick-textured and rigid, the apices acute, acuminate or awned; plants native or introduced, uncommon to very common in SK; NOT [Glumes and lemmas distinctly thick-textured, rigid and usually blunt- tipped (glumes sometimes mucronate, lemmas occasionally awned); plants introduced, rare in SK]
Lemmas unawned or with awns straight or somewhat flexuous; if awns strongly outcurving, then at midspike the spikelets twice as long as the rachis internodes or longer and extending beyond 2 nodes, and the lemmas usually pubescent; NOT [Lemma awns strongly outcurving; at midspike the spikelets the same length as the rachis internodes or 1.5 times as long and extending into the middle of the next internode; lemmas glabrous]
Plants without the below combination of characteristics: if the glumes as below then the leaf blade surfaces not markedly different; NOT [Glumes widest at or near base, not widening at midlength or beyond; the longer glume about as long as the lowest lemma; leaf blades to 4.5 mm wide, stiff, usually glaucous, tapering to a sharp point, usually angled away from the culm at a fixed angle approaching 45; the prominently ridged adaxial surface markedly different from the smooth abaxial surface; plants with creeping rhizomes]

 

Repens: Answers to key questions leading to this species. 
Spikelets 1 per node (occasionally 2 at some nodes); glumes lanceolate or wider (except E. glaucus which may have linear-lanceolate glumes); NOT [Spikelets 2 or more per node (occasionally 1 at some nodes); glumes setaceous to linear-lanceolate]
Lemmas usually glabrous; the lower glume usually 3/4 as long to longer than the adjacent lemma; glumes flat or distinctly keeled distally; lemma awns, if > 2 mm long, then straight or somewhat flexuous at maturity; leaf blades seldom involute, usually flat, 2-17 mm wide; culms growing in tufts without rhizomes (or with very short rhizomes) or singly from long, thick, creeping rhizomes; NOT [Lemmas usually pubescent; the lower (shorter) glume usually 1/2 to 2/3 as long as the adjacent lemma; glumes flat or weakly keeled; lemma awns, if > 2mm long, then usually curved outward at maturity; leaf blades involute, seldom flat, 1 6 mm wide; culms growing in loose tufts from slender, creeping rhizomes]
Plants with long, creeping rhizomes; glumes distinctly keeled distally (at least some glumes in spike), the keel usually extending into either a smooth, blunt or a scabrous, tapered awn to 3 mm long; lemma unawned or with awns to 4 (10) mm long; anthers (3) 4-7 mm long; auricles well-developed; collars on lower leaves divided, often puberulent; NOT [Plants tufted with dense fibrous roots, rhizomes absent or very short; glumes flat distally or occasionally weakly keeled, the tips unawned or tapering into slender, scabrous awns to 11 mm long; lemma unawned or with awns to 40 mm long; anthers 1.5-3.5 mm long; auricles present, absent or rudimentary; collars divided or continuous, glabrous]