1	"Callus hairs more than 1.3 times as long as the lemmas; lemmas at least 2 mm shorter than the glumes, long-acuminate"	"Calamagrostis epigejos"
1	"Callus hairs usually less than 1.2 times as long as the lemmas; if the callus hairs longer than the lemmas, then the lemmas less than 2 mm shorter than the glumes and not long-acuminate"	2
2	"Blades usually densely hairy on the adaxial surfaces; glumes keeled, scabrous; awns 4.5–9 mm long"	"Calamagrostis purpurascens"
2	"Blades glabrous or sparsely hairy on the adaxial surfaces; glumes keeled or rounded, scabrous or smooth; awns 0.5–17 mm long"	3
3	"Leaves with abundant white glands between the veins, visible at about 10×; awns 5–8 mm long; plants of California"	"Calamagrostis ophitidis"
3	"Leaves without abundant white glands between the veins; awns 0.5–17 mm long; plants from throughout the Flora region, including California"	4
4	"Awns 5–17 mm long, always exserted and bent; if the awns 5–6 mm long, either some blades wider than 2 mm or the abaxial blade surfaces scabrous."	5
4	"Awns 0.5–6 mm long, exserted or not, bent or straight; if the awns 5–6 mm long, then either all blades less than 2 mm wide or the abaxial blade surfaces smooth or nearly so"	9
5	"Panicles open, (2)3.5–6.5(8) cm wide when pressed, branches spikelet-bearing only beyond midlength; awns 10–16 mm long"	"Calamagrostis howellii"
5	"Panicles usually contracted, (0.5)0.8–3 cm wide if open, the branches spikelet-bearing to below midlength, usually to the base; awns 5–17 mm long."	6
6	"Some leaf blades 6–13 mm wide; culms (47)60–120(150) cm tall"	"Calamagrostis tweedyi"
6	"All leaf blades (1.5)2–7 mm wide; culms (15)30–60(95) cm tall, if the culms taller than 60 cm, then the blades less than 4 mm wide."	7
7	"Awns 12–14(17) mm long; plants of California"	"Calamagrostis foliosa"
7	"Awns (5.4)7–11(13) mm long; plants of Alaska, British Columbia, Washington, and Oregon."	8
8	"Glume apices long-acuminate, usually twisted distally; glume keels usually scabrous for their whole length"	"Calamagrostis sesquiflora"
8	"Glume apices usually acute, if acuminate, not twisted distally; glume keels smooth or sparsely scabrous on the distal 1/2"	"Calamagrostis tacomensis"
9	"Awns attached on the distal 2/5 of the lemmas, 0.5–2 mm long, straight; blades flat; panicles contracted, 0.7–2.5(3) cm wide"	10
9	"Awns attached on the lower 1/2(7/10) of the lemmas, 0.9–6 mm long, straight or bent; blades flat or involute; panicles open or contracted, 0.4–5.5(9) cm wide"	11
10	"Lateral veins of the glumes prominent; rachillas hairy only distally"	"Calamagrostis cinnoides"
10	"Lateral veins of the glumes obscure; rachillas hairy throughout their length"	"Calamagrostis scopulorum"
11	"Blades 0.2–1.7 mm wide; panicles (1.5)1.9–8.5 cm long; callus hairs sparse"	12
11	"Blades (1)1.5–20 mm wide, most wider than 2 mm; panicles (2)3–30(40) cm long; callus hairs sparse to abundant"	13
12	"Blades involute, 0.2–0.4 mm in diameter; ligules 1–2.5 mm long"	"Calamagrostis muiriana"
12	"Blades flat, 0.9–1.7 mm wide, sometimes involute and 0.4–0.6 mm in diameter when dry; ligules 1.7–6 mm long"	"Calamagrostis breweri"
13	"Awns usually exserted, (2.8)3–6 mm long; callus hairs 0.1–0.7 times as long as the lemmas; leaf collars hairy or glabrous"	14
13	"Awns usually not exserted, or if exserted, then barely so, 0.9–3.1(4) mm long; callus hairs (0.1)0.2–1.2(1.5) times as long as the lemmas; leaf collars glabrous or hairy, if hairy, then the callus hairs more than 0.7 times as long as the lemmas"	20
14	"Culms 10–55(60) cm tall; panicles open; blades (1)1.5–3(4) mm wide"	15
14	"Culms (26)50–210 cm tall; panicles open or contracted; blades (1)1.5–8(12) mm wide, most blades wider than 3 mm"	16
15	"Blades 2–8(15) cm long; panicles erect; plants of brackish arctic and subarctic coastal habitats"	"Calamagrostis deschampsioides"
15	"Blades (5)15–39 cm long; panicles often drooping; plants of rocky soils and disturbed sites in the mountains of Tennessee and North Carolina"	"Calamagrostis cainii"
16	"Panicles open, 2.5–6 cm wide; panicle branches with the spikelets confined to the distal 1/4–1/2; leaf collars glabrous"	"Calamagrostis bolanderi"
16	"Panicles usually contracted, 0.7–3(7) cm wide; panicle branches usually with the spikelets confined to the distal 1/2–2/3, sometimes spikelet-bearing to the base; leaf collars hairy or glabrous."	17
17	"Culms 135–210 cm tall; plants cultivated ornamentals"	"Calamagrostis x acutiflora"
17	"Culms 26–120 cm tall; plants native."	18
18	"Awns 4–5.5 mm long; leaf collars glabrous; plants often densely cespitose; rhizomes usually 2–4 mm thick"	"Calamagrostis koelerioides"
18	"Awns 2–4.5 mm long; leaf collars sometimes hairy; plants loosely cespitose; rhizomes 0.5–2 mm thick."	19
19	"Blades (2)3–8(12) mm wide; panicle branches usually with the spikelets restricted to the distal 1/2–2/3, sometimes spikelet-bearing to the base; plants from east of the 100th meridian"	"Calamagrostis porteri"
19	"Blades (1)2–5(8) mm wide; panicle branches spikelet-bearing to the base; plants from west of the 100th meridian"	"Calamagrostis rubescens"
20	"Callus hairs shorter than 1 mm, 0.2–0.3 times as long as the lemmas; awns bent"	"Calamagrostis pickeringii"
20	"Callus hairs longer than 1 mm, (0.2)0.3–1.2(1.5) times as long as the lemmas; awns straight or bent."	21
21	"Culms usually scabrous, rarely smooth; awns slightly bent; callus hairs 0.4–0.8 times as long as the lemmas; blades usually involute, 1–4 mm wide, the abaxial surfaces scabrous; nodes 1–2"	"Calamagrostis montanensis"
21	"Culms smooth to slightly scabrous; awns usually straight, rarely bent; callus hairs (0.2)0.5–1.2(1.5) times as long as the lemmas; blades flat or involute, 1–20 mm wide, the abaxial surfaces smooth or scabrous; nodes 1–8."	22
22	"Lemmas (3)4–5 mm long; glumes keeled; blades flat"	"Calamagrostis nutkaensis"
22	"Lemmas 2–4(5) mm long, if the lemmas longer than 4 mm, then the glumes rounded and the abaxial blade surfaces smooth; glumes keeled or rounded; blades flat or involute."	23
23	"Panicle branches 2.7–6.5(12) cm long; ligules lacerate; glumes scabrous on the keels, often throughout; blades flat, the abaxial surfaces scabridulous or scabrous; nodes (2)3–7(8); panicles open."	24
23	"Panicle branches (1)1.4–5(9.5) cm long; if the panicle branches longer than 3.7 cm, then the ligules usually entire; glumes smooth or scabrous only on the keels; blades flat or involute, the abaxial surfaces smooth or scabrous; nodes 1–3(4); panicles loosely contracted"	25
24	"Awns bent, stout, readily distinguished from the callus hairs; collars densely hairy; plants of New York State"	"Calamagrostis perplexa"
24	"Awns usually straight, delicate, often difficult to distinguish from the callus hairs; collars rarely hairy; plants of northern and western North America"	"Calamagrostis canadensis"
25	"Glume lengths usually more than 3 times the widths, smooth, the keels rarely slightly scabrous, the lateral veins obscure; spikelets 3.5–5.5 mm long; awns usually slender and similar to the callus hairs"	"Calamagrostis lapponica"
25	"Glume lengths usually less than 3 times the widths, usually smooth, rarely scabrous, the keels smooth or scabrous, the lateral veins prominent or obscure; spikelets 2–5 mm long; awns stout, usually readily distinguished from the callus hairs"	"Calamagrostis stricta"