1	"Spikelets laterally compressed, lengths 1–4 times widths, oval in side view; paleal keels not winged"	2
1	"Spikelets cylindrical and terete, except at anthesis when slightly laterally compressed, lengths more than 5 times widths, rectangular in side view; paleal keels usually winged distally"	11
2	"Upper glumes 2.5–5 mm long, longer than wide"	3
2	"Upper glumes 0.6–3.7 mm long, if longer than 3 mm, then shorter than wide"	4
3	"Blades 3–7 mm wide; culms 2.5–4 mm thick, 60–90 cm tall; anthers 0.7–1.2 mm long"	"Glyceria alnasteretum"
3	"Blades 6–20 mm wide; culms 6–12 mm thick, 60–250 cm tall; anthers (1)1.2–2 mm long"	"Glyceria maxima"
4	"Panicles ovoid to linear; panicle branches appressed to strongly ascending; ligules of the upper leaves 0.5–0.9 mm long"	5
4	"Panicles pyramidal; panicle branches strongly divergent or drooping; ligules of the upper leaves 1–7 mm long"	6
5	"Panicles 5–15 cm long, 2.5–6 cm wide, ovoid, erect"	"Glyceria obtusa"
5	"Panicles 15–25 cm long, 0.8–1.5 cm wide, linear, nodding"	"Glyceria melicaria"
6	"Lemma apices almost flat; anthers 3; veins of 1 or both glumes in each spikelet usually extending to the apices"	"Glyceria grandis"
6	"Lemma apices prow-shaped; anthers 2; veins of both glumes terminating below the apices"	7
7	"Glumes tapering from below midlength to the narrowly acute (< 45°) apices; lemma lengths more than twice widths"	"Glyceria nubigena"
7	"Glumes narrowing from midlength or above to the acute (> 45°) or rounded apices; lemma lengths less than twice widths"	8
8	"Spikelets (2.5)3–5 mm wide; lemma veins evident but not raised distally; palea lengths 1.5–1.8 times widths"	"Glyceria canadensis"
8	"Spikelets 1.2–2.9 mm wide; lemma veins distinctly raised throughout; palea lengths 1.5–3.5 times widths"	9
9	"Lemmas 2.5–3.5 mm long; glume lengths about 3 times widths, glume apices broadly acute; lower glumes 1.5–2 mm long; upper glumes 2–2.6 mm long"	"Glyceria pulchella"
9	"Lemmas 1.2–2.2 mm long; glume lengths up to twice widths, glume apices rounded or acute; lower glumes 0.5–1.5 mm long; upper glumes 0.6–1.5 mm long"	10
10	"Blades 2–6 mm wide; anthers 0.2–0.6 mm long; culms 1.5–3.5 mm thick"	"Glyceria striata"
10	"Blades 6–15 mm wide; anthers 0.5–0.8 mm long; culms 2.5–8 mm thick"	"Glyceria elata"
11	"Lemmas tapering from near midlength to the acuminate or narrowly acute apices; paleas exceeding the lemmas by 0.7–3 mm; palea apices often appearing bifid, the teeth 0.4–1 mm long"	"Glyceria acutiflora"
11	"Lemmas not tapered or tapering only in the distal 1/4, apices truncate, rounded, or acute; paleas shorter or to 1(1.5) mm longer than the lemmas; palea apices not or shortly bifid, the teeth to 0.5 mm long"	12
12	"Lemma apices with 1 strongly developed lobe on 1 or both sides, entire to crenulate between the lobes; blades 3–12 cm long; primary panicle branches 1.5–9.5 cm long"	"Glyceria declinata"
12	"Lemma apices not or more or less evenly lobed; blades 5–30 cm long; primary panicle branches 3–18 cm long"	13
13	"Lemmas 5–8 mm long"	14
13	"Lemmas 2.4–5 mm long"	15
14	"Anthers 0.6–1.6 mm long; lemma apices usually slightly lobed or irregularly crenate"	"Glyceria X occidentalis"
14	"Anthers 1.5–3 mm long; lemma apices usually entire"	"Glyceria fluitans"
15	"Lemmas usually smooth between the veins, if scabridulous the prickles between the veins smaller than those over the veins"	16
15	"Lemmas scabridulous or hispidulous between the veins, the prickles between the veins similar in size to those over the veins"	18
16	"Lemmas usually acute, sometimes obtuse, entire or almost so; adaxial surfaces of the midcauline blades usually densely papillose, glabrous"	"Glyceria borealis"
16	"Lemmas truncate to obtuse, crenate; adaxial surfaces of the midcauline blades rarely densely papillose, sometimes sparsely hairy"	17
17	"Culms 73–182 cm tall; pedicels 0.7–1.7 mm"	"Glyceria septentrionalis"
17	"Culms 25–80 cm tall; pedicels 1–6 mm"	"Glyceria notata"
18	"Lemma apices acute"	19
18	"Lemma apices truncate to obtuse"	20
19	"Lemmas 2.4–4.8 mm long; pedicels 0.7–1.7 mm long; plants from east of the Rocky Mountains"	"Glyceria septentrionalis"
19	"Lemmas 4.5–5.9 mm long; pedicels 1.5–8 mm long; plants from west of the Rocky Mountains"	"Glyceria X occidentalis"
20	"Pedicels 0.7–1.7 mm long; anthers 0.5–1.8 mm long; plants from east of the Rocky Mountains"	"Glyceria septentrionalis"
20	"Pedicels 2–5 mm long; anthers 0.3–0.9 mm long; plants from British Columbia and the Pacific states"	"Glyceria leptostachya"