1	"Paleas at least 2/5 as long as the lemmas"	2
1	"Paleas absent or less than 2/5 as long as the lemmas"	8
2	"Lemmas 0.5–0.8 mm long, transparent; paleas similar to the lemmas and almost as long; panicles usually over 1/2 the length of the culms, extremely diffuse"	"Agrostis nebulosa"
2	"Lemmas 1.2–2.5 mm long, opaque to translucent; paleas shorter than the lemmas; panicles less than 1/2 the length of the culms, diffuse or not"	3
3	"Panicles narrowly contracted, sometimes open at anthesis, 0.5–4(6) cm wide; branches ascending to appressed"	4
3	"Panicles open at maturity, sometimes somewhat contracted after anthesis, (1)2–15 cm wide; branches spreading to ascending"	5
4	"Stolons present, plants mat-forming, rhizomes absent; paleas 0.7–1.4 mm long; anthers 0.9–1.4 mm long"	"Agrostis stolonifera"
4	"Stolons absent, plants usually cespitose, rhizomes sometimes present; paleas to 0.5 mm long; anthers 0.3–0.6 mm long"	"Agrostis exarata"
5	"Ligules of the upper leaves longer than wide, 2–7.5 mm long; usually at least some lower panicle branches with spikelets to the base"	6
5	"Ligules of the upper leaves usually shorter than wide, 0.3–3 mm long; lower panicle branches with spikelets confined to the distal 1/3–1/2"	7
6	"Stolons absent, rhizomes present; culms 20–120 cm tall; panicles 8–30 cm long; longest lower panicle branches 4–9 cm long"	"Agrostis gigantea"
6	"Stolons present, rhizomes absent; culms 8–60 cm tall; panicles 3–20 cm long; longest lower panicle branches 2–6 cm long"	"Agrostis stolonifera"
7	"Calluses glabrous or with a few hairs to 0.1 mm long; adjacent pedicels divergent, giving well-separated spikelets; panicles stiffly erect, 3–20 cm long; awns rarely present, to 2 mm; lemmas glabrous"	"Agrostis capillaris"
7	"Calluses abundantly hairy, hairs to 0.6 mm long; adjacent pedicels not divergent, spikelets appearing clustered; panicles somewhat lax, 10–30 cm long; awns, if present, to 5 mm long on the terminal spikelet of a cluster; lemmas occasionally with hairs on the lower 1/2"	"Agrostis castellana"
8	"Lemmas awned"	9
8	"Lemmas unawned"	29
9	"Panicles dense, often spikelike, 0.2–4 cm wide; lower branches usually shorter than 2 cm, appressed to ascending, usually hidden by the spikelets"	10
9	"Panicles open or diffuse, or somewhat contracted but not spikelike, 0.4–20 cm wide; lower branches 1.5–12 cm long, erect to spreading, readily visible"	17
10	"Lemma awns 3.5–10 mm long; calluses with hairs to 1 mm long; plants annual"	11
10	"Lemma awns to 3.5 mm long; calluses glabrous or with hairs to 0.3 mm long; plants perennial"	12
11	"Lemmas 2.5–4 mm long, teeth to 1.5 mm long; awns (5)8–10 mm long; blades 1–4.5 cm long"	"Agrostis hendersonii"
11	"Lemmas 1.5–2.3 mm long, teeth to 0.5 mm long; awns 3.5–8 mm long; blades 3–15 cm long"	"Agrostis microphylla"
12	"Blades less than 2 mm wide, usually involute or folded"	13
12	"Blades 2–10 mm wide, usually flat, sometimes folded"	15
13	"Calluses glabrous; panicles often partly enclosed by the upper sheaths at maturity; lemma awns to 0.7 mm long"	"Agrostis blasdalei"
13	"Calluses hairy; panicles exserted from the upper sheaths at maturity; lemma awns to 3.5 mm long"	14
14	"Lemma apices acute, entire; lemma awns to 2.8 mm long, usually not exserted from the spikelets"	"Agrostis variabilis"
14	"Lemma apices truncate, denticulate; lemma awns 2–3.5 mm long, exserted from the spikelets"	"Agrostis tolucensis"
15	"Lemma apices truncate to acute; blades to 4 mm wide, flat or involute; ligules 2–6.2 mm long; panicles 0.5–1.5 cm wide"	"Agrostis tolucensis"
15	"Lemma apices acute to obtuse; blades to 10 mm wide, flat; ligules 1–11.2 mm long; panicles 0.5–4 cm wide"	16
16	"Anthers 0.3–0.6 mm long; paleas usually absent, rarely to 0.5 mm long and about 1/5 the length of the lemmas; lemmas entire or with teeth to 0.12 mm long"	"Agrostis exarata"
16	"Anthers 0.5–2 mm long; paleas 0.3–0.7 mm long, to about 1/3 the length of the lemmas; lemmas usually with teeth to 0.3 mm long"	"Agrostis densiflora"
17	"Leaves usually involute or becoming so, sometimes only the basal leaves involute, less than 1 mm in diameter when involute, 0.5–2 mm wide when flat; plants without rhizomes or stolons"	18
17	"Leaves usually remaining flat, 0.5–6 mm wide; plants with or without rhizomes or stolons"	21
18	"Anthers 1, 0.1–0.2 mm long, usually persistent at the apices of the caryopses; awns attached just below the apices of the lemmas, flexuous but not geniculate, deciduous"	"Agrostis elliottiana"
18	"Anthers 3, 0.4–1.5 mm long, usually shed at anthesis; awns attached below midlength on the lemmas, usually geniculate, persistent"	19
19	"Basal leaves usually withered at anthesis; lower sheaths finely tomentose; callus hairs abundant; plants endemic to coastal California"	"Agrostis hooveri"
19	"Basal leaves persistent; lower sheaths smooth or scabrous; callus hairs sparse; plants widespread, especially in northern and montane parts of the Flora region, including California"	20
20	"Panicles (2)3–10 cm long; branches not capillary, fairly stiff, smooth or sparsely scabridulous; callus hairs to 0.4 mm long; caryopses 1.4–2 mm long, endosperm solid"	"Agrostis mertensii"
20	"Panicles (4)8–25(50) cm long; branches capillary, flexible, scabrous; callus hairs to 0.2 mm long; caryopses 0.9–1.4 mm long; endosperm liquid"	"Agrostis scabra"
21	"Lemmas with 4 teeth up to 0.5 mm long, lemmas 2.5–3 mm long; awns 4–6 mm long"	"Agrostis howellii"
21	"Lemmas usually entire, sometimes minutely toothed or erose, teeth to 0.4 mm long, lemmas 1–3 mm long; awns to 5 mm long"	22
22	"Rhizomes and stolons absent; blades to 30 cm long; anthers 0.4–1.2 mm long"	23
22	"Rhizomes or stolons present; blades 1–10 cm long; anthers 0.7–1.8 mm long"	27
23	"Panicle branches widely divergent, the whole panicle often detaching at the base at maturity, forming a tumbleweed; cauline nodes usually 1–3; blades 1–2 mm wide; glume apices acuminate"	"Agrostis scabra"
23	"Panicle branches usually erect to ascending, if widely divergent then the panicle not forming a tumbleweed; cauline nodes 2–10; blades 0.5–5 mm wide; glume apices acute to acuminate"	24
24	"Lemma awns 1–4.4 mm long, geniculate, exserted; blades to 13 cm long"	25
24	"Lemma awns minute or to 2 mm long, straight, usually not exserted; blades 6–30 cm long"	26
25	"Leaf blades 0.5–3 mm wide, flat to involute; panicles 2–10 cm long, usually open; awns 2–4.4 mm long, inserted just below midlength on the lemmas"	"Agrostis mertensii"
25	"Leaf blades 3–4 mm wide, flat; panicles 6–20 cm long, somewhat contracted; awns 1–1.5 mm long, inserted just above midlength on the lemmas"	"Agrostis anadyrensis"
26	"Basal leaves usually withered by anthesis; culm leaves 3–10, as broad and substantial as the lower leaves; callus hairs dense; plants primarily from east of the 100th Meridian"	"Agrostis perennans"
26	"Basal leaves persisting; culm leaves 5 or fewer, usually less substantial than the lower leaves; callus hairs sparse; plants primarily western"	"Agrostis oregonensis"
27	"Rhizomes absent; stolons present, to about 25 cm long, producing tufts of shoots at the nodes; glumes 1.7–3 mm long; panicles open, branches erect to spreading"	"Agrostis canina"
27	"Rhizomes present, to about 10 cm long; stolons absent; glumes 2–4 mm long; panicles open to constricted, branches more or less erect to ascending"	28
28	"Lemma apices blunt, entire; lemmas usually awned from near the base, rarely unawned, awns 2–4.5 mm long, geniculate"	"Agrostis vinealis"
28	"Lemma apices acute, entire or toothed; lemmas usually unawned, rarely awned from below the apices, awns to 0.5(2.7) mm long, straight"	"Agrostis pallens"
29	"Mature panicles dense; lower panicle branches to 3(4) cm long, often hidden by the spikelets; spikelets crowded"	30
29	"Mature panicles open to diffuse; lower panicle branches often longer than 3 cm, usually not hidden by the spikelets; spikelets crowded or not"	33
30	"Blades 0.5–2 mm wide, in dense basal tufts; panicles 0.2–2 cm wide; culms 5–30 cm tall"	31
30	"Blades 2–10 mm wide, not basally concentrated; panicles 0.5–4 cm wide; culms 8–100 cm tall"	32
31	"Lemma veins not excurrent; anthers 0.4–1 mm long; plants of western alpine and subalpine zones"	"Agrostis variabilis"
31	"Lemma veins excurrent to 0.2 mm; anthers 0.7–2 mm long; plants of western coastal cliffs, dunes, and shrublands"	"Agrostis blasdalei"
32	"Anthers 0.3–0.6 mm long; paleas usually absent, rarely to 0.5 mm long and about 1/5 the length of the lemmas; lemmas entire or with teeth to 0.12 mm long"	"Agrostis exarata"
32	"Anthers 0.5–2 mm long; paleas 0.3–0.7 mm long, to about 1/3 the length of the lemmas; lemmas usually toothed, teeth to 0.3 mm long"	"Agrostis densiflora"
33	"Blades 0.5–14 cm long, 0.5–2 mm wide, usually involute or becoming so; anthers 0.1–0.9 mm long"	34
33	"Blades 1–30 cm long, 1–7.5 mm wide, usually flat; anthers 0.3–2.3 mm long"	38
34	"Anthers 1, 0.1–0.2 mm long; callus hairs dense, to 0.6 mm long; plants annual"	"Agrostis elliottiana"
34	"Anthers 3, 0.2–0.9 mm long; callus hairs sparse, to 0.3 mm long; plants perennial or annual"	35
35	"Panicles (4)8–50 cm long; lower panicle branches 4–15 cm long"	36
35	"Panicles 1.5–13 cm long; lower panicle branches 1–4 cm long"	37
36	"Lemmas 1.4–2 mm long, exceeding the ripe caryopses by 0.3+ mm; anthers 0.4–0.8 mm long; pedicels to 9.6 mm long, spikelets not appearing clustered"	"Agrostis scabra"
36	"Lemmas 0.8–1.2 mm long, exceeding the ripe caryopses by no more than 0.2 mm; anthers 0.2–0.5 mm long; pedicels to 3.5 mm long, spikelets appearing clustered"	"Agrostis hyemalis"
37	"Anthers 0.3–0.6 mm long; upper culm sheaths not inflated; plants perennial, of western seepage areas and bogs"	"Agrostis idahoensis"
37	"Anthers 0.5–0.9 mm long; upper culm sheaths inflated; plants annual, near hot springs"	"Agrostis rossiae"
38	"Rhizomes present, to 50 cm long, stolons absent; panicle branches branching from midlength or to near the base; lower panicle branches 1–5 cm long; anthers 0.7–2.3 mm long"	39
38	"Rhizomes absent, stolons sometimes present, to 25 cm long; panicle branches mostly branching at or beyond midlength; lower panicle branches 1–12 cm long; anthers 0.3–1.5 mm long"	41
39	"Lemma apices blunt, entire; callus hairs sparse, to 0.1 mm long; panicles 2–15 cm long; pedicels 0.5–2 mm long; blades 1–3 mm wide"	"Agrostis vinealis"
39	"Lemma apices usually acute, entire or toothed, teeth to about 0.2 mm long; callus hairs sparse or abundant, to 2 mm long; panicles 5–22 cm long; pedicels 0.5–7 mm long; blades 1–6 mm wide"	40
40	"Anthers 0.7–1.8 mm long; callus hairs to 0.3(1) mm long, sparse; leaf blades 1.5–11.5 cm long; caryopses 1–1.5 mm long"	"Agrostis pallens"
40	"Anthers 1.5–2.3 mm long; callus hairs 0.8–2 mm long, abundant; leaf blades 6–20 cm long; caryopses 1.5–2 mm long"	"Agrostis hallii"
41	"Stolons present, to about 25 cm long, producing tufts of shoots at the nodes; anthers 1–1.5 mm long; blades 1–3 mm wide; glume apices acute"	"Agrostis canina"
41	"Stolons absent; anthers 0.3–1.2 mm long; blades 0.5–7 mm wide; glume apices acute to acuminate"	42
42	"Blades to 2 mm wide, 1–14 cm long, flat or involute; leaves mostly basal"	43
42	"Blades to 7 mm wide, usually at least some wider than 2 mm, 5–30 cm long, flat; leaves mostly cauline to mostly basal"	44
43	"Lower panicle branches 4–12 cm long; whole panicle often detaching at the base at maturity, forming a tumbleweed; blades 4–14 cm long"	"Agrostis scabra"
43	"Lower panicle branches 1–4 cm long; panicle not detaching at maturity and forming a tumbleweed; blades 1–7 cm long"	"Agrostis idahoensis"
44	"Plants annual or short-lived perennials; glumes 1.5–2.8 mm long, subequal; lemmas smooth and glabrous; anthers 0.3–0.6 mm long; caryopses 0.9–1.3 long"	"Agrostis clavata"
44	"Plants perennial; glumes 1.8–3.6 mm long, unequal; lemmas smooth or scabridulous, sometimes pubescent; anthers 0.4–1.2 mm long; caryopses 1–1.9 mm long"	45
45	"Basal leaves usually withered by anthesis; cauline nodes 3–10; blades of the upper leaves as broad and substantial as those of the lower leaves; callus hairs abundant; plants primarily from east of the 100th Meridian"	"Agrostis perennans"
45	"Basal leaves persisting to anthesis; cauline nodes 5 or fewer; blades of the upper leaves usually less substantial than those of the lower leaves; callus hairs sparse; plants primarily western"	"Agrostis oregonensis"