14.27 AGROSTIS L.
M.J. Harvey

Plants usually perennial; usually cespitose, sometimes rhizomatous or stoloniferous. Culms (3)5–120 cm, usually erect. Sheaths open, usually smooth and glabrous, sometimes scabrous to scabridulous, rarely hairy; collars not strongly developed; auricles absent; ligules membranous, smooth or scabridulous dorsally, apices truncate, obtuse, rounded, or acute, usually erose to lacerate, the lacerations sometimes obscuring the shape, or entire; blades flat, folded, or involute, usually smooth and glabrous, sometimes scabridulous, adaxial surfaces somewhat ridged. Inflorescences terminal panicles, narrowly cylindrical and dense to open and diffuse; branches usually in whorls, usually more or less scabrous, rarely smooth, some branches longer than 1 cm; secondary panicles sometimes present in the leaf axils. Spikelets 1.2–7 mm, pedicellate, laterally compressed, lanceolate to narrowly oblong or ovate, with 1(2) florets; rachillas not prolonged beyond the base of the floret(s); disarticulation above the glumes, beneath the florets, sometimes initially at the panicle base. Glumes (1)1.3–2(4) times longer than the lemmas, 1(3)-veined, glabrous, usually mostly smooth, vein(s) often scabrous to scabridulous, backs keeled or rounded, apices acute to acuminate or awn-tipped; lower glumes usually 0.1–0.3 mm longer than the upper glumes, rarely equal; calluses poorly developed, blunt, glabrous or hairy, hairs to about 1/2 as long as the lemmas; lemmas thinly membranous to hyaline, usually smooth and glabrous, sometimes scabridulous, occasionally pubescent, rarely warty-tuberculate, 3–5-veined, veins not convergent, sometimes excurrent as 2–5 teeth, apices acute to obtuse or truncate, sometimes erose, unawned or awned, sometimes varying within an inflorescence, awns arising from near the lemma bases to near the apices, usually geniculate, sometimes straight; paleas absent, or minute to subequal to the lemmas, usually thin, veins not or only weakly developed; lodicules 2, free; anthers (1)3, 0.1–2 mm, not penicillate; styles 2, free to the base, white; ovaries glabrous. Caryopses with a hard, soft, or liquid endosperm, the latter resulting from the substitution of lipids for starch. x = 7. Name from the Greek agros, ‘pasture’ or ‘green fodder’.

Agrostis in the older, broad sense is a genus comprised of species with the spikelets reduced to single florets. As such, it is found in all inhabited continents, is presumably of ancient origins, and many of the 150–200 species may be only distantly related. The shortage of clear-cut morphological features has hindered its subdivision into more natural units. This treatment follows Edgar (1995), Edgar and Connor (2000), and Jacobs (2001) in placing A. avenacea J.F. Gmel. in the Australasian genus Lachnagrostis, as L. filiformis; Rúgolo de Agrasar (1982) in treating A. tandilensis (Kuntze) Parodi as Bromidium tandilense; and Soreng (2003) in placing A. aequivalvis (Trin.) Trin. and A. humilis —together with several Central and South American species, including A. sesquiflora E. Desv.—in the genus Podagrostis.

Agrostis usually differs from both Podagrostis and Lachnagrostis in having no, or very reduced, paleas, and in rachillas that are not prolonged beyond the base of the floret. Some of the Eurasian species of Agrostis are exceptional in having paleas at least 2/5 as long as the lemmas. Agrostis also differs from Lachnagrostis in certain features of the lemma epidermes (Jacobs 2001).

Agrostis is sometimes confused with Apera, Calamagrostis, or Polypogon. It differs from Apera in having lemmas that are less firm than the glumes, paleas that are often absent or minute, and in lacking a rachilla prolongation. There is no single character that distinguishes all species of Agrostis from those of Calamagrostis. In general, Agrostis has smaller plants with smaller, less substantial lemmas and paleas than Calamagrostis, and tends to occupy drier habitats. It differs from Polypogon in having spikelets that disarticulate above the glumes.

Some taxonomists used the presence of a trichodium net for circumscribing Trichodium Michx. This net is formed by a series of transverse thickening bars developed on the inner wall of the dorsal epidermal cells of the lemma, and is found in several different genera, usually in species with a reduced palea.

Species of Agrostis growing in the temperate regions of the Northern Hemisphere and on tropical mountains are mostly perennials, with the annual species predominantly in warmer climates, such as the Mediterranean and the Southern Hemisphere. Of the 26 species known from the Flora region, 21 are native and 5 are introductions. Two additional species, A. tolucensis and A. anadyrensis, have been reported; the reports are dubious.

Some species of Agrostis make a modest contribution to forage, a few are agricultural weeds, and some are excellent lawn grasses in cool climates. Most North American native species are narrow habitat specialists, with many being western endemics. The introduced species are all widely distributed in temperate regions of the world.

Unusual specimens of Agrostis with elongate or leafy spikelets are caused by infection with the nematode Anguillina agrostis. Other pathogens may cause stunting.

Species with awns on the lemmas frequently exhibit a developmental gradient within the inflorescence. Upper florets may possess a well-developed geniculate awn inserted at the base or on the lower half of the lemma; mid-inflorescence spikelets may have a shorter, possibly non-geniculate awn inserted high on the lemma, while basal spikelets may possess only a terminal bristle on the lemma. This phenomenon is particularly sharply shown in Agrostis castellana, where a single side branch of only a dozen or so spikelets can show the whole sequence. When using the key, it is advised to examine spikelets from the upper parts of an inflorescence. Many species key more than once, due to the potential for awns to be either present or absent.

SELECTED REFERENCES Björkman, S.O. 1960. Studies in Agrostis and related genera. Symb. Bot. Upsal. 17:1–112; Carlbom, C.G. 1967. A biosystematic study of some North American species of Agrostis L. and Podagrostis (Griesb.) Scribn. & Merr. Ph.D. dissertation, Oregon State University, Corvallis, Oregon, U.S.A. 232 pp.; Edgar, E. 1995. New Zealand species of Deyeuxia P. Beauv. and Lachnagrostis Trin. (Gramineae: Aveneae). New Zealand J. Bot. 33:1–33; Edgar, E. and H.E. Connor. 2000. Flora of New Zealand, vol. 5. Manaaki Whenua Press, Lincoln, New Zealand. 650 pp.; Hitchcock, A.S. 1951. Manual of the Grasses of the United States, ed. 2, rev. A. Chase. U.S.D.A. Miscellaneous Publication No. 200. U.S. Government Printing Office, Washington, D.C., U.S.A. 1051 pp.; Jacobs, S.W.L. 2001. The genus Lachnagrostis (Gramineae) in Australia. Telopea 9:439–448; Romero García, A.T., G. Blanca Lopez, and C. Morales Torres. 1988. Revisión del género Agrostis L. (Poaceae) en la Península Ibérica. Ruizia 7:1–160; Rúgolo de Agrasar, Z.E. 1982. Revalidación del género Bromidium Nees et Meyen emend. Pilger (Gramineae). Darwiniana 24:187–216; Rúgolo de Agrasar, Z.E. and A.M. Molina. 1997. Las especies del género Agrostis L. (Gramineae: Agrostideae) de Chile. Gayana, Bot. 54:91–156; Soreng, R.J. 2003. Podagrostis. Contr. U.S. Natl. Herb. 48:581; Tercek, M.T., D.P. Hauber, and S.P. Darwin. 2003. Genetic and historical relationships among thermally adapted Agrostis (Bentgrass) of North America and Kamchatka: Evidence for a previously unrecognized, thermally adapted taxon. Amer. J. Bot. 90:1306–1312; Tsvelev, N.N. 1976. Zlaki SSSR. Nauka, Leningrad [St. Petersburg], Russia. 788 pp.

[For an interactive dichotomous key, click here; the interactive, multientry key has not yet been posted].

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 ..... A. 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 ..... A. stolonifera (in part)
4. Stolons absent, plants usually cespitose, rhizomes sometimes present; paleas to 0.5 mm long; anthers 0.3–0.6 mm long..... A. exarata (in part)
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 ..... A. gigantea
6. Stolons present, rhizomes absent; culms 8–60 cm tall; panicles 3–20 cm long; longest lower panicle branches 2–6 cm long ..... A. stolonifera (in part)
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 ..... A. 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 ..... A. 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 ..... A. 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 ..... A. 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 ..... A. blasdalei (in part)
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 ..... A. variabilis (in part)
14. Lemma apices truncate, denticulate; lemma awns 2–3.5 mm long, exserted from the spikelets ..... A. tolucensis (in part)
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 .... A. tolucensis (in part)
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 ..... A. exarata (in part)
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 ..... A. densiflora (in part)
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 ..... A. elliottiana (in part)
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 ..... A. 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 ..... A. mertensii (in part)
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 ..... A. scabra (in part)
21. Lemmas with 4 teeth up to 0.5 mm long, lemmas 2.5–3 mm long; awns 4–6 mm long ..... A. 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 ..... A. scabra (in part)
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 ..... A. mertensii (in part)
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 ..... A. 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 ..... A. perennans (in part)
26. Basal leaves persisting; culm leaves 5 or fewer, usually less substantial than the lower leaves; callus hairs sparse; plants primarily western ..... A. oregonensis (in part)
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 ..... A. canina (in part)
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 ..... A. vinealis (in part)
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 ..... A. pallens (in part)
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 ..... A. variabilis (in part)
31. Lemma veins excurrent to 0.2 mm; anthers 0.7–2 mm long; plants of western coastal cliffs, dunes, and shrublands ..... A. blasdalei (in part)
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 ..... A. exarata (in part)
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 ..... A. densiflora (in part)
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 ..... A. elliottiana (in part)
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 ..... A. scabra (in part)
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 ..... A. hyemalis
37. Anthers 0.3–0.6 mm long; upper culm sheaths not inflated; plants perennial, of western seepage areas and bogs ..... A. idahoensis (in part)
37. Anthers 0.5–0.9 mm long; upper culm sheaths inflated; plants annual, near hot springs ..... A. 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 ..... A. vinealis (in part)
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 ..... A. pallens (in part)
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 ..... A. 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 ..... A. canina (in part)
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 ..... A. scabra (in part)
43. Lower panicle branches 1–4 cm long; panicle not detaching at maturity and forming a tumbleweed; blades 1–7 cm long ..... A. idahoensis (in part)
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 ..... A. 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 ..... A. perennans (in part)
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 ..... A. oregonensis (in part)

1. Agrostis capillaris L.
Browntop, Rhode Island Bent, Colonial Bent, Agrostide Fine

Plants perennial; rhizomatous or stoloniferous, rhizomes or stolons to 5 cm. Culms 10–75 cm, erect or geniculate, with 2–5 nodes. Leaves basal and cauline; sheaths smooth; ligules 0.3–2 mm, shorter than wide, dorsal surfaces usually scab-ridulous, sometimes smooth, apices truncate to rounded, erose-ciliolate, sometimes lacerate; blades 3–10 cm long, 1–5 mm wide, flat. Panicles 3–20 cm long, less than 1/2 the length of the culm, (1)2–12 cm wide, stiffly erect, widely ovate, open, exserted from the upper sheaths at maturity, lowest node with (2)3–9(13) branches; branches smooth or scabridulous, spreading during and after anthesis, spikelets usually confined to the distal 1/2, lower branches 1.5–7 cm; pedicels 0.4–3.3 mm, adjacent pedicels divergent. Spikelets lanceolate or oblong, purplish brown to greenish. Glumes subequal, 1.7–3 mm, 1-veined, acute; lower glumes scabridulous over the midvein towards the apices; upper glumes scabridulous or smooth over the midvein; calluses glabrous, or with a few hairs to 0.1 mm; lemmas 1.2–2.5 mm, smooth, glabrous, opaque to translucent, 3(5)-veined, veins typically prominent, apices obtuse to acute, usually entire, sometimes the veins excurrent to 0.5 mm, usually unawned, rarely awned, sometimes varying within a panicle, awns to 2 mm, mid-dorsal, straight or geniculate; paleas 0.6–1.2(1.4) mm, typically at least 1/2 the length of the lemmas, veins visible; anthers 3, 0.8–1.3 mm. Caryopses 0.8–1.5 mm; endosperm solid. 2n = 28.

Agrostis capillaris grows along roadsides and in disturbed areas. It was introduced from Europe, and is now well established in western and eastern North America. It is often used for fine-leaved lawns; commercial seed sold as Agrostis tenuis ‘Highland’ usually contains A. capillaris.

Agrostis capillaris differs from A. gigantea in its short ligules, especially on the vegetative shoots, and the open panicles that lack spikelets near the base of the branches. It differs from A. castellana in having diffuse rather than clustered spikelets, fewer rhizomes, divaricate panicle branches after anthesis, calluses that are glabrous or with hairs up to 0.1 mm long, and glabrous lemmas. It also tends to flower somewhat earlier than A. castellana. Agrostis capillaris readily hybridizes with A. vinealis, the hybrids being somewhat intermediate between the two parents.

2. Agrostis castellana Boiss. & Reut.
Highland Bent, Dryland Browntop

Plants perennial; loosely cespitose, rhizomatous, rhizomes to 10(40) cm, covered with inflated scales. Culms 30–80 cm, erect or geniculate, with up to 10 nodes, basal internodes devoid of leaf bases after anthesis in dry habitats, shoots proliferating from the upper nodes, especially of the innovations, later in the season. Leaves mostly cauline; sheaths smooth; ligules 0.5–3 mm, shorter than wide, dorsal surfaces smooth or scabridulous, apices truncate to rounded, ciliolate-erose; blades 4–10 cm long, 1–3 mm wide, flat. Panicles 10–30 cm long, less than 1/2 the length of the culm, 3–8 cm wide, loosely ovate, somewhat lax, somewhat contracted and linear-lanceolate after anthesis, lowest node with (1)2–7 branches; branches spreading to ascending, sparsely scabridulous, branching above the midpoint, spikelets usually confined to the distal 1/3 and in discrete clusters at the branch tips, lower branches 3–9 cm; pedicels 0.6–2.3(3) mm, usually shorter than the spikelets, adjacent pedicels not divergent. Spikelets lanceolate, yellowish green to stramineous or brownish, slightly to strongly suffused with purple. Glumes subequal, 2–3 mm, lanceolate, 1-veined, acute or acuminate; lower glumes scabrous over the midvein, at least distally; upper glumes smooth or scabrous to scabridulous over the midvein distally; calluses abundantly hairy, hairs to 0.3(0.6) mm; lemmas 1.3–1.9 mm, occasionally with hairs on the lower 1/2, translucent, (3)5-veined, veins prominent distally, apices usually truncate to obtuse, sometimes acute, entire or the lateral veins excurrent to 0.6 mm, awned or unawned, usually mixed in the inflorescence, terminal spikelets usually awned, in some plants all unawned, awns to 5 mm, awns arising from the lower 1/3 or occasionally as a minute bristle from above the center; paleas 0.6–1.1 mm, 1/2–2/3 as long as the lemma; anthers 3, 1–1.5 mm. Caryopses about 1 mm. 2n = 28, 42.

Agrostis castellana is native to southern Europe. It was introduced to North America in the 1930s for use in lawns and golf greens, under the name Agrostis tenuis ‘Highland’; commercial samples of ‘Highland’ often contain A. capillaris. Escaped plants were collected at least as early as the 1950s, but were not recognized as belonging to A. castellana until the 1990s, when several collections were identified as such in Oregon. Recorded habitats have ranged from sunny gravel roadsides to moist ground alongside cranberry bogs, at elevations from near sea level to over 600 m. In view of its extensive commercial use for over 70 years and its drought tolerance, it is likely that it is more widespread than shown.

Agrostis castellana belongs to a Eurasian group that includes A. gigantea, A. stolonifera, and A. capillaris. It differs from A. gigantea and A. stolonifera in having shorter, truncate ligules about as short as wide, and in not possessing extensive rhizomes and stolons. It differs from A. capillaris in having clustered rather than diffuse spikelets, more abundant rhizomes, somewhat constricted panicle branches after anthesis, abundantly hairy calluses with hairs up to 0.3(0.6) mm long, and lemmas that are sometimes dorsally pubescent. It also tends to flower somewhat later than A. capillaris.

3. Agrostis gigantea Roth
Redtop, Agrostide Blanche

Plants perennial; rhizomatous, rhizomes to 25 cm, not stolon-iferous. Culms 20–120 cm, erect, sometimes geniculate at the base, sometimes rooting at the lower nodes, with 4–7 nodes. Leaves mostly cauline, sheaths smooth or sparsely scabridulous; ligules longer than wide, dorsal surfaces usually scabrous, sometimes smooth, apices rounded to truncate, erose to lacerate, basal ligules 1–4.5 mm, upper ligules 2–7 mm; blades 4–10 cm long, 3–8 mm wide, flat. Panicles 8–25(30) cm long, less than 1/2 the length of the culm, (1.5)3–15 cm wide, erect, open, broadly ovate, exserted from the upper sheaths at maturity, lowest node with (1)3–8 branches; branches scabrous, spreading during and after anthesis, usually some branches spikelet-bearing to the base, lower branches 4–9 cm, usually with many shorter secondary branches resulting in crowding of the spikelets, spikelets restricted to the distal 1/2 of the branches and not crowded in shade plants; pedicels 0.3–3.4(4.2) mm. Spikelets narrowly ovate to lance-olate, green and slightly to strongly suffused with purple. Glumes subequal, 1.7–3.2 mm, lanceolate, 1-veined, acute to apiculate; lower glumes scabrous on the distal 1/2 of the midvein; upper glumes scabridulous on the distal 1/2 of the midvein; callus hairs to 0.5 mm, sparse; lemmas 1.5–2.2 mm, opaque to translucent, smooth, 3–5-veined, veins usually obscure, sometimes prominent throughout or distally, often excurrent to 0.2 mm, apices usually acute, sometimes obtuse or truncate, usually unawned, rarely with a 0.4–1.5(3) mm straight awn arising from near the apices to near the base; paleas 0.7–1.4 mm, about 1/2 the length of the lemmas, veins visible; anthers 3, 1–1.4 mm. Caryopses 1–1.5 mm; endosperm solid. 2n = 42.

Agrostis gigantea grows in fields, roadsides, ditches, and other disturbed habitats, mostly at lower elevations. It is a serious agricultural weed, as well as a valuable soil stabilizer. In the Flora region, its range extends from the subarctic to Mexico; it is considered to be native to Eurasia. It is more heat tolerant than most species of Agrostis.

Agrostis gigantea has been confused with A. stolonifera, from which it differs in having rhizomes and a more open panicle. Agrostis stolonifera has elongated leafy stolons, mainly all above the surface, that root at the nodes, and the panicles are condensed and often less strongly pigmented than in A. gigantea. Its distribution tends to be more northern and coastal where ditches and pond margins are common habitats, and its stolons enable it to form loose mats. Agrostis gigantea is ecologically adapted to a more extreme climate—hot summers/cold winters and drought—than A. stolonifera. It is also similar to A. capillaris and A. castellana; it differs from both in its longer ligules, from A. capillaris in its less open panicles with spikelets near the base of the branches, and from A. castellana in being more extensively rhizomatous.

When Agrostis gigantea grows in damp hollows under trees it becomes more like A. stolonifera, particularly when the inflorescence is young, not expanded, and pale. If the rootstock is not collected, identification is a major problem.

4. Agrostis stolonifera L.
Creeping Bent, Agrostide Stolonifère

Plants perennial; stoloniferous, stolons 5–100+ cm, rooting at the nodes, often forming a dense mat, without rhizomes. Culms (8)15–60 cm, erect from a geniculate base, sometimes rooting at the lower nodes, with (2)4–7 nodes. Leaves mostly cauline; sheaths smooth; ligules longer than wide, dorsal surfaces usually scabrous, rarely smooth, apices usually rounded, acute to truncate, erose to lacerate, basal ligules 0.7–4 mm, upper ligules 3–7.5 mm; blades 2–10 cm long, 2–6 mm wide, flat. Panicles (3)4–20 cm long, less than 1/2 the length of the culm, 0.5–3(6) cm wide, narrowly contracted, dense, oblong to lanceolate, exserted from the sheaths at maturity, lowest node with 1–7 branches; branches scabrous, ascending to appressed, except briefly spreading during anthesis, usually some branches at each node spikelet-bearing to the base, lower branches 2–6 cm; pedicels 0.3–3.3 mm. Spikelets lanceolate, green and slightly to strongly suffused with purple. Glumes subequal to unequal, 1.6–3 mm, lanceolate, 1-veined, sometimes scabridulous distally, at least on the midvein, acute to acuminate or apiculate; callus hairs to 0.5 mm, sparse; lemmas 1.4–2 mm, opaque to translucent, smooth, 5-veined, veins obscure or prominent distally, apices acute to obtuse, entire or the veins excurrent to about 0.1 mm, usually unawned, rarely with a subapical straight awn to about 1 mm; paleas 0.7–1.4 mm, veins visible; anthers 3, 0.9–1.4 mm. Caryopses 0.9–1.3 mm; endosperm solid. 2n = 28, 35, 42.

Agrostis stolonifera grows in areas that are often temporarily flooded, such as lakesides, marshes, salt marshes, lawns, and damp fields, as well as moist meadows, forest openings, and along streams. It will also colonize disturbed sites such as ditches, clearcuts, and overgrazed pastures. Its North American range extends from the subarctic into Mexico, mostly at low to middle elevations.

Agrostis stolonifera has been confused with A. gigantea. It is considered to be Eurasian, but some northern salt marsh and lakeside populations may be native. Agrostis stolonifera is also similar to A. castellana; it differs in having longer, acute to truncate ligules that are longer than wide, and in possessing extensive stolons. The names A. palustris Huds. and A. maritima Lam. have been applied to plants with longer stolons; all forms intergrade. A hybrid between A. stolonifera and Polypogon monspeliensis, ×Agropogon lutosus, has been found in the Flora region. It differs from A. stolonifera in having awned glumes and lemmas. Agrostis stolonifera readily hybridizes with A. vinealis, the hybrids being somewhat intermediate between the two parents.

5. Agrostis canina L.
Velvet Bent, Agrostide des Chiens

Plants perennial; appearing loosely cespitose and forming a rather closed turf, stoloniferous, stolons to 25 cm, slender, leafy, weakly rooting and eventually producing tufts of shoots at the nodes, without rhizomes. Culms 15–75 cm, erect, frequently geniculate at the base, some-times weakly rooting at the lower nodes, with 2–4(6) nodes. Leaves basal and cauline; sheaths usually smooth, sometimes scabrous distally; ligules 1–4 mm, dorsal surfaces scabridulous, apices truncate to obtuse or acute, erose-lacerate; blades 1–10 cm long, 1–3 mm wide, usually flat, sometimes involute, usually scabrous, apices acute. Panicles 3–10 cm long, 1–7 cm wide, open, often lax, lanceolate to broadly ovate, lowest node with 3–7 branches; branches more or less scabrous, erect to spreading, usually branched above midlength, spikelet-bearing in the distal 1/3, patent at anthesis, lower branches 3–5 cm; pedicels (0.4)1–3 mm. Spikelets lanceolate or narrowly oblong, brownish yellow to purplish or rarely greenish. Glumes subequal, 1.7–3 mm, 1-veined, scabrous only on the distal part of the midveins, acute; callus hairs to 0.1 mm; lemmas 1–2 mm, about 2/3 the length of the glumes, bases minutely pubescent, otherwise glabrous, translucent to opaque, 5-veined, veins prominent or obscure, apices acute to obtuse, entire, usually awned from near the base, awns to 5 mm, geniculate, rarely unawned, awned and unawned lemmas sometimes mixed within the panicle; paleas absent, or to about 0.2 mm and thin; anthers 3, 1–1.5 mm, at least 1/2 as long as the lemmas. Caryopses 0.8–1.2 mm; endosperm solid. 2n = 14.

Agrostis canina is a Eurasian species that is now established in both western and eastern North America, where it grows on roadsides and open ground in summer-cool climates. It is used for fine-textured lawns and golf greens. Similar to A. vinealis, it may be differentiated from that species by its creeping, leafy stolons that form a dense carpet, and the finer, softer texture of its leaves. Unawned plants have been called A. canina var. mutica G. Sinclair.

6. Agrostis vinealis Schreb.
Brown Bent

Plants perennial; densely ces-pitose, rhizomatous, rhizomes to about 10 cm, slender, scaly, not stoloniferous. Culms 10–60 cm, erect or geniculate at the base, slender, smooth, with 1–2(4) nodes. Sheaths smooth; ligules 0.6–5 mm, dorsal sur-faces scabridulous, apices acute to obtuse, entire or lacerate to erose; blades 2–10 cm long, 1–3 mm wide, usually flat, sometimes involute, sometimes bristlelike, adaxial surfaces scabrous, abaxial surfaces sometimes scabrous. Panicles 2–15 cm long, (0.8)1–5.5(8) cm wide, lanceolate to oblong, somewhat open, often contracted after anthesis, lowest node with (1)3–8 branches; branches scabrous, readily visible, more or less erect, branched mostly at or below midlength, spikelets closely clustered, lower branches 3–5 cm; pedicels 0.5–2 mm. Spikelets lanceolate to narrowly oblong, greenish, purplish, or brownish. Glumes equal to subequal, 2–4 mm, membranous, acute to acuminate; lower glumes 1-veined, scabrous to scabridulous over the midvein; upper glumes usually shorter than the lower glumes, 1(3)-veined, almost smooth; callus hairs to 0.1 mm, sparse; lemmas 1.5–2.4 mm, about 3/4 the length of the glumes, bases minutely pubescent, glabrous and smooth elsewhere, translucent to opaque, 5-veined, veins usually prominent distally, apices blunt, entire, usually awned from near the base, awns 2–4.5 mm, geniculate, rarely unawned; paleas to about 0.2 mm; anthers 3, 1–1.8 mm. Caryopses 0.8–1.3 mm; endosperm solid. 2n = 28.

Agrostis vinealis is native to Eurasia; it is not clear if populations in Greenland and Alaska represent a circumboreal distribution, or are introductions. It forms a fine, compact turf. It is similar to A. canina in its habitat, except that it appears to be more heat tolerant and drought resistant. It used to be included in A. canina, but differs from that species in its subterranean rhizomes and lack of leafy stolons. Agrostis vinealis readily hybridizes with A. capillaris and A. stolonifera, the hybrids being somewhat intermediate between the two parents.

7. Agrostis mertensii Trin.
Northern Bent, Agrostide de Mertens

Plants perennial; cespitose, not rhizomatous or stoloniferous. Culms (5)10–40 cm, erect, with 2–4 nodes. Leaves mostly basal or basal and cauline, basal leaves persistent; sheaths smooth or scabrous; ligules 0.7–3.3 mm, scabridulous or smooth, usually rounded, sometimes acute or truncate, erose, sometimes lacerate; blades 2.5–13 cm long, 0.5–3 mm wide, usually flat, occasionally involute or folded. Panicles (2)3–10 cm long, (0.5)1.5–5 cm wide, widely ovate to lanceolate, usually open, exserted from the upper sheaths at maturity, lowest node with (1)2–5 branches; branches erect, not capillary, readily visible, smooth or sparsely scabridulous, branched above midlength, spikelets in the distal 1/2 or beyond, lower branches (1.5)2–4 cm; pedicels 0.4–6.4 mm. Spikelets lanceolate to narrowly ovate, dark brown or purplish. Glumes subequal, 2–4 mm, elliptical to lanceolate, midveins scabrous to scabridulous, at least distally, 1-veined, acute; callus hairs to 0.4 mm, sparse; lemmas 1.6–2.6 mm, smooth or scabridulous, translucent to opaque, 5-veined, veins prominent to obscure, apices acute, entire or erose, awned from just below midlength, awns (2)3–4.4 mm, geniculate, exserted, persistent; paleas absent, or to 0.1 mm and thin; anthers 3, 0.5–0.8 mm, usually shed at anthesis. Caryopses 1.4–2 mm; endosperm solid. 2n = 56 [reports of 2n = 42 are for Agrostis scabra].

Agrostis mertensii grows on banks and gravel bars in river and lake valleys, and on open grasslands and rocky slopes of mountains and cliffs. It has a circumboreal distribution. In the Flora region, it extends from Alaska across Canada to Newfoundland and Greenland, south in the mountains to Wyoming and Colorado in the west, and West Virginia, Tennessee, and North Carolina in the east. It also grows in arctic Europe, Scandinavia, the mountainous regions of Mexico, and northwestern South America, where some unusually robust specimens have been somewhat dubiously referred to this species.

Agrostis mertensii is frequently confused with dwarf, awned forms of A. scabra, but has larger spikelets, more culm nodes, larger anthers, slightly wider, flatter leaves, and panicles that are less expanded and less than 1/3 the culm length. Agrostis mertensii is also often confused with A. idahoensis, but A. mertensii tends to grow in better-drained habitats. Agrostis mertensii differs from A. anadyrensis in being less robust, having narrower, less abundant basal leaves, smaller panicles, and minor differences in the insertion of the awns on the lemmas. In addition, the panicle branches are smooth to weakly scabrous, contrasting with the branches of A. anadyrensis, which are strongly scabrous, with long acicules throughout their length.

8. Agrostis anadyrensis Soczava
Anadyr Bent

Plants perennial; loosely cespitose, not rhizomatous or stoloniferous. Culms 20–50 cm, erect. Basal leaves usually numerous; ligules 0.6–3.5 mm, scabridulous, rounded, erose, sometimes lacerate, ciliate; blades to 10 cm long, 3–4 mm wide, flat. Panicles 6–20 cm long, 1–4(8) cm wide, lanceolate to ovate, somewhat contracted but not spikelike; branches erect, slender, scabrous; pedicels 0.5–8 mm. Spikelets lanceolate, greenish purple. Glumes subequal, 2–3.5 mm, 1-veined, ciliate on the keels, otherwise smooth, acute; callus hairs less than 1/6 the length of the lemma; lemmas 1.6–3 mm, translucent, 5-veined, veins obscure or prominent distally, apices acute, entire, awned from above midlength, awns 1–1.5 mm, geniculate, exserted; paleas absent; anthers 3, 0.5–0.8 mm. 2n = 56.

Agrostis anadyrensis grows in sand and gravel shores of rivers and lakes, and in meadows and shrubby valleys in eastern Siberia. It has been reported by Tsvelev (1976) from arctic Russia and southern Alaska. Specimens from Alaska purporting to be A. anadyrensis so far have proven to be A. mertensii. Agrostis anadyrensis differs from A. mertensii in being more robust, with wider, more abundant basal leaves, larger panicles, and minor differences in the insertion of the awns on the lemmas. In addition, the panicle branches are strongly scabrous, with long acicules throughout their length, contrasting with the smooth to weakly scabrous branches of A. mertensii.

9. Agrostis clavata Trin.
Clavate Bent

Plants annuals or short-lived perennials; densely tufted, not rhizomatous or stoloniferous. Culms 30–70 cm, erect, smooth, with 3–6 nodes. Leaves mostly basal or basal and cauline; sheaths smooth; ligules (0.5) 1.5–4.2 mm, dorsal surfaces scabrous, apices truncate to rounded, erose-lacerate, often ciliolate; blades 10–20 cm long, 1–5(7) mm wide, flat, scabrous at least along the margins and/or veins. Panicles 8–35 cm long, 3–10 cm wide, widely ovate, becoming lax, open, usually exserted, bases sometimes enclosed in the upper sheaths at maturity, lowest node with (1)2–8 branches; branches scabrous, spreading, branched above midlength, spikelet-bearing in the distal 1/2–2/3, lower branches 3–12 cm; pedicels 0.5–5.5 mm, clavate; secondary panicles often present in the leaf axils, smaller than the primary panicles. Spikelets narrowly ovate to lanceolate, greenish or light brownish purple. Glumes subequal, 1.5–2.8 mm, lanceolate, 1-veined, keels somewhat aculeolate, apices usually acute, sometimes acuminate; calluses usually sparsely hairy, hairs to 0.2 mm, sometimes glabrous; lemmas 1.2–2 mm, smooth, glabrous, translucent to opaque, 5-veined, veins prominent distally or obscure, apices acute, entire, unawned; paleas absent, or to 0.2 mm and thin; anthers 3, 0.3–0.6 mm, to 1/2 as long as the lemmas. Caryopses 0.9–1.3 mm. 2n = [28], 42.

Agrostis clavata grows in disturbed ground on sandbars and gravelbars, and in wet meadows and coniferous forests, from Sweden across northern Asia to Kamchatka. It was recently found in Alaska, the Yukon, and the Northwest Territories, and appears to be native there. It differs from the similarly large-panicled A. scabra in its much broader, flat leaves.

10. Agrostis scabra Willd.
Ticklegrass, Rough Bent, Foin Fou, Agrostide Scabre

Plants perennial or annual; cespitose, not rhizomatous or stoloniferous. Culms (7.5) 15–90 cm, erect, nodes usually 1–3. Leaves mostly basal, basal leaves usually persistent; sheaths usually smooth, sometimes scabridulous; ligules 0.7–5 mm, dorsal surfaces scabrous, apices usually rounded, sometimes truncate or acute, erose-ciliolate, sometimes lacerate; blades 4–14 cm long, 1–2 mm wide, basal blades mostly involute, cauline blades mostly flat. Panicles (4)8–25(50) cm long, 0.5–20 cm wide, broadly ovate, often nearly as wide as long, diffuse, the whole panicle often detaching at the base at maturity, forming a tumbleweed, exserted from the upper sheaths, lowest node with (1)2–7(12) branches; branches scabrous, capillary, flexible, wide-spreading, readily visible, branching beyond midlength, spikelets somewhat distant, not crowded, lower branches 4–12 cm; pedicels 0.4–9.6 mm. Spikelets lanceolate, greenish purple, frequently purple at maturity. Glumes unequal, 1.8–3.4 mm, lanceolate, 1-veined, keels scabrous at least towards the apices, apices acuminate; callus hairs to 0.2 mm, sparse; lemmas 1.4–2 mm, scabrous to scabridulous or smooth, translucent to opaque, 5-veined, veins prominent, apices acute to obtuse, usually entire, sometimes minutely toothed, unawned or awned from below midlength, awns 0.2–3 mm, exceeding the lemma apices by up to 2.5 mm, geniculate or straight, persistent; paleas absent or to 0.2 mm; anthers 3, 0.4–0.8 mm, usually shed at anthesis. Caryopses 0.9–1.4 mm; endosperm liquid. 2n = 42.

Agrostis scabra grows in a wide variety of habitats, including grasslands, meadows, shrublands, wood-lands, marshes, and stream and lake margins, as well as disturbed sites such as roadsides, ditches, and aban-doned pastures. It occurs throughout much of the Flora region, but is not common in the Canadian high arctic or the southeastern United States. It extends south into Mexico; it is also native to the Pacific coast from Kamchatka to Japan and Korea, and has been introduced elsewhere.

Plants in the Agrostis scabra aggregate are variable. Awned and unawned plants often occur together, the difference presumably being caused by a single gene. At least three groups may be distinguished within the species as treated here: widespread, lowland, rather weedy plants capable of producing very large panicles that have been introduced into the southern United States; smaller, short-leaved, slow-growing plants of rocks and screes, which are widespread in the Rockies, the Appalachians, and much of Alaska, Canada, and Greenland; and luxuriant, broad-leaved plants that are characteristically found in sheltered, frost-free canyons of the southwestern United States. The second group has sometimes been called A. scabra var. geminata (Trin.) Swallen or A. geminata Trin.

Tercek et al. (2003) found that annual forms of Agrostis scabra with inflated upper sheaths and open panicles that were collected around hot springs in western North America were molecularly, and in some respects morphologically, more similar to plants identified as hot spring endemics such as A. rossiae and A. pauzhetica Prob., than they were to neighboring perennial plants of A. scabra that did not have inflated leaf sheaths. They differed, however, in having open, rather than contracted, panicles.

Agrostis scabra is often confused with a number of other species; for comparisons, see under the appropriate species description: A. mertensii, A. clavata, A. hyemalis, A. perennans, and A. idahoensis.

11. Agrostis hyemalis (Walter) Britton, Sterns & Poggenb.
Winter Bent, Agrostide d’Hiver

Plants perennials or facultative annuals; cespitose, not rhizom-atous or stoloniferous. Culms 15–82 cm, erect, with (3)4–7 nodes. Leaves cauline and basal; sheaths smooth; ligules (0.7) 1.2–4 mm, dorsal surfaces scab-rous, apices usually rounded to truncate, sometimes acute, lacerate-erose; blades 3–10 cm long, 1–2 mm wide, flat, becoming involute, or folded. Panicles (5)10–25(36) cm long, (3)4–24 cm wide, broadly ovate, often nearly as wide as long, diffuse, the whole panicle often detaching at the base at maturity, forming a tumbleweed, bases often enclosed by the upper sheaths, lowest node with (3)5–11 branches; branches scabrous, capillary, flexible, wide-spreading, branching in the distal 1/4, spikelets strongly clustered at the branch tips, lower branches 5–15 cm; pedicels 0.1–2.5(3.5) mm. Spikelets ovate to narrowly ovate, greenish or purplish. Glumes subequal, 1–2 mm, 1-veined, keeled, keels scabrous, sometimes the body also scabrous towards the apices, acute to acuminate; callus hairs to 0.2 mm, sparse; lemmas 0.8–1.2 mm, scabridulous, translucent to opaque, 5-veined, veins obscure or prominent distally, apices usually obtuse, sometimes acute, entire, unawned; paleas absent, or to 0.2 mm and thin; anthers 3, 0.2–0.5 mm. Caryopses 0.7–1 mm. 2n = 28.

Agrostis hyemalis is most abundant along roadsides and in open pastures, scrub, and rocky areas. It is centered in the southeastern United States; historically it extended north to coastal Maine, where it may be extinct, west to Wisconsin and Texas, and south into the Caribbean, Mexico, and Ecuador. Records from further north and west in North America are confused; many reflect the former inclusion of the generally more northern A. scabra in A. hyemalis. Agrostis hyemalis differs from A. scabra in its smaller spikelets and anthers, more conspicuous culm leaves, and more clustered spikelets.

12. Agrostis perennans (Walter) Tuck.
Autumn Bent, Upland Bent, Agrostide Perennant

Plants perennial; cespitose, not rhizomatous or stoloniferous. Culms 20–80 cm, erect, sometimes rooting at the lower nodes, with 3–10 nodes. Leaves usually mostly cauline, basal leaves withering at anthesis; sheaths usually smooth, some-times scabridulous, ligules (0.7)1.5–7.3 mm, dorsal surfaces scabrous, apices acute to truncate, erose to lacerate, often ciliolate; blades 6–20 cm long, 2–5 mm wide, flat, lax to stiff, cauline blades as substantial as the basal blades. Panicles 10–25 cm long, 2.5–11 cm wide, broadly ovate, open, bases usually exserted, sometimes enclosed in the upper sheaths at maturity, lowest node with (1)3–11(13) branches; branches scabridulous, capillary, wide-spreading, branching above midlength, spikelets somewhat aggregated towards the ends of the branches, lower branches 3–7 cm; pedicels 1–7.3 mm, spreading; secondary panicles sometimes present in the leaf axils. Spikelets lanceolate to narrowly ovate, green to tawny. Glumes unequal, 1.8–3.2 mm, lower glumes longer than the upper glumes, 1-veined, veins scabrous, acuminate to acute; callus hairs to 0.3 mm, abundant; lemmas 1.3–2.2 mm, smooth or scabridulous, translucent, 5-veined, veins prominent to obscure, apices acute to more or less truncate, entire or minutely denticulate, usually unawned, rarely awned from near midlength, awns to 2 mm, straight, not exserted; paleas absent, or to 0.1 mm and thin; anthers 3, 0.4–0.9 mm. Caryopses 1.1–1.9 mm; endosperm liquid. 2n = 42.

Agrostis perennans grows along roadsides and in fields, fens, woodlands, and periodically inundated stream banks. It is widespread and common in eastern North America; it also grows from central Mexico to central South America. There are old records from Oregon and Washington, but A. perennans does not appear to be established in western North America. It is more tolerant of shade and moisture than Agrostis scabra, from which it differs in its later flowering, leafier culms, and its basal leaves that usually wither by anthesis.

13. Agrostis idahoensis Nash
Idaho Redtop

Plants perennial; cespitose, not rhizomatous or stoloniferous. Culms 8–40 cm, slender, erect, with 2–5 nodes. Leaves mostly basal; sheaths usually smooth, sometimes scabridulous, not inflated; ligules (0.7)1–3.8 mm, dorsal surfaces scabridulous, apices rounded to truncate, rarely acute, erose to lacerate; blades 1–7 cm long, 0.5–2 mm wide, flat, becoming involute. Panicles 3–13 cm long, 1–6(8) cm wide, lanceolate to ovate, diffuse, exserted from the upper sheaths at maturity, lowest node with 1–6(10) branches; branches scabridulous, fairly stiff, more or less ascending, branching at or above midlength, spikelets not crowded, frequently solitary, lower branches 1–4 cm; pedicels 0.5–6.4 mm. Spikelets lanceolate to narrowly ovate, purplish. Glumes subequal, 1.5–2.5 mm, 1-veined, usually scabrous to scabridulous, upper glumes sometimes smooth, apices acute to acuminate; callus hairs to 0.3 mm, sparse; lemmas 1.2–2.2 mm, usually smooth, sometimes scabridulous, translucent to opaque, 5-veined, veins usually prominent at least distally, sometimes obscure, apices acute to obtuse, entire, unawned; paleas absent, or to 0.2 mm and thin; anthers 3, 0.3–0.6 mm. Caryopses 1–1.3 mm. 2n = 28.

Agrostis idahoensis grows in western North America, from British Columbia to California and New Mexico, in alpine and subalpine meadows along wet seepage areas and bogs, and in wet openings with Sphagnum in coniferous forests. It was recently discovered in Chile and Argentina; it is not known whether it is native or introduced there (Rúgolo de Agrasar and Molina 1997). Agrostis idahoensis is often confused with A. mertensii and dwarf forms of A. scabra, both of which tend to grow in better-drained habitats.

14. Agrostis oregonensis Vasey
Oregon Redtop

Plants perennial; cespitose, not rhizomatous or stoloniferous. Culms 12–75 cm, erect, with up to 5 nodes. Leaves mostly basal, basal leaves usually persistent; sheaths smooth or scabridulous, ligules 1.2–6.3 mm, usually scabridulous, sometimes smooth, truncate to rounded, lacerate-erose; blades 10–30 cm long, (1)2–4 mm wide, flat, culm blades usually less substantial than the basal blades. Panicles 8–35(60) cm long, (1.5)2.5–14 cm wide, lanceolate-ovate, usually 3 times longer than wide, open, bases exserted from the upper sheaths at maturity, lowest node with 1–15 branches; branches scabrous to scabridulous, ascending, mostly branching above midlength, lower branches occasionally branching to near the base, spikelets somewhat clustered towards the tips, lower branches 2–10 cm, mostly longer than 3 cm; pedicels (0.5)1–3.5(6) mm; secondary panicles not present. Spikelets lanceolate to narrowly ovate, yellowish green to purple. Glumes unequal, 2–3.6 mm, 1(3)-veined, scabrous on the midvein, occasionally also sparsely scabridulous over the body, acute to acuminate; callus hairs to 0.2 mm, sparse; lemmas 1.5–2.5 mm, usually smooth, sometimes scabridulous or pubescent, translucent to opaque, 5-veined, veins faint or prominent distally, apices acute to obtuse, usually entire, sometimes erose or toothed, teeth to about 0.4 mm, usually unawned, sometimes awned from midlength, awns to 2 mm, straight, not exserted, sometimes awned and unawned spikelets present on the same plant; paleas absent, or to 0.2 mm and thin; anthers 3, 0.5–1.2 mm. Caryopses 1–1.6 mm; endosperm semisoft. 2n = 42.

Agrostis oregonensis grows in wet habitats, such as stream and lake margins, damp woods, and meadows, in western North America, primarily in the Pacific Northwest from British Columbia to California and Wyoming. It has not been found in Mexico.

15. Agrostis exarata Trin.
Spike Bent

Plants perennial; usually cespitose, sometimes rhizomatous, not stoloniferous. Culms 8–100 cm, erect or decumbent at the base, sometimes rooting at the lower nodes, with (2)3–6(8) nodes. Leaves mostly cauline; sheaths smooth or slightly scabrous; ligules (1)1.7–8(11.2) mm, dorsal surfaces scabrous, apices truncate to obtuse, lacerate to erose; blades 4–15 cm long, 2–7 mm wide, flat. Panicles (3)5–30 cm long, 0.5–4 cm wide, contracted, spikelike, oblong, or lanceolate, usually dense, rarely more open, sometimes interrupted near the base, bases usually exserted, rarely enclosed by the upper sheaths at maturity, lowest node with 1–5 branches; branches scabrous, ascending to appressed, spikelet-bearing to or near the base, usually hidden by the spikelets, spikelets crowded, lower branches 1–2(4) cm; pedicels 0.2–4.3 mm. Spikelets lanceolate to narrowly ovate, greenish to purplish. Glumes subequal to equal, 1.5–3.5 mm, scabrous on the midvein and sometimes on the back, 1(3)-veined, acute, elongate-acuminate, with an awnlike tip to 1 mm; callus hairs to 0.3 mm, sparse to abundant; lemmas 1.2–2.2 mm, smooth, translucent to opaque, 5-veined, veins prominent distally or obscure throughout, apices acute, entire or toothed, teeth no more than 0.12 mm, unawned or awned from above midlength, awns to 3.5 mm, straight or geniculate; paleas absent or to 0.5 mm; anthers 3, 0.3–0.6 mm. Caryopses 0.9–1.2 mm; endosperm solid or soft. 2n = 28, 42, 56.

Agrostis exarata is common and widely distributed in western North America, usually growing in moist ground in open woodlands, river valleys, tidal marshes, and swamp and lake margins; it also grows in dry habitats such as grasslands and shrublands. It extends from Alaska into Mexico, and is also found in Kamchatka and the Kuril Islands. Eastern North American records probably reflect introductions. It readily colonizes roadsides and bare soil, and exhibits ecological and developmental flexibility. Agrostis exarata is recognized here as a single, variable species that includes what others have treated as distinct species or varieties. Cytotaxonomic study might clarify the basis of the observed variation. Agrostis exarata appears to be related to A. densiflora.

16. Agrostis densiflora Vasey
California Bent

Plants perennial; not rhizom-atous or stoloniferous. Culms 9–85 cm, erect, sometimes decumbent at the base, some-times rooting at the lower nodes, usually with 4–7 nodes. Leaves basal and cauline; sheaths smooth or scabrous; ligules 1–4.8(7.5) mm, dorsal surfaces scabrous, apices truncate to obtuse, erose-lacerate, sometimes ciliolate; blades 2–12 cm long, 2–10 mm wide, upper blades broader than those below, flat. Panicles 2–10 cm long, 0.5–2 cm wide, narrow and spikelike to dense, lobed-lanceolate, bases exserted or enclosed by the upper sheaths at maturity; branches to 1.5 cm, scabrous, appressed, branching at the base and mostly hidden by the spikelets; pedicels about 0.4–3 mm. Spikelets lanceolate to narrowly ovate, yellowish, sometimes tinged with purple, or greenish purple. Glumes generally equal, 2–3.3 mm, 1-veined, densely scabrous, aculeolate on the veins, narrowly acute to acuminate or somewhat mucronate, mucros to about 0.5 mm; callus hairs to 0.3 mm, usually dense; lemmas 1.5–2.1 mm, smooth or scabridulous, translucent, (3)5-veined, veins prominent to obscure, sometimes prominent only distally, apices acute to obtuse, veins usually extended as teeth up to 0.3 mm, unawned or awned from above midlength, awns to 3.5 mm, straight, readily deciduous; paleas 0.3–0.7 mm, thin; anthers 3, 0.5–2 mm. Caryopses 1–1.5 mm; endosperm solid. 2n = 42.

Agrostis densiflora is endemic to coastal Oregon and California. It grows in sandy soils, on cliffs, and in scrublands. It appears to be related to A. exarata, and hybridizes with A. blasdalei.

17. Agrostis pallens Trin.
Dune Bent

Plants perennial; rhizomatous, rhizomes to 10 cm, not stolon-iferous. Culms 10–70 cm, erect, sometimes decumbent at the base, sometimes rooting at the lower nodes, with 3–7 nodes. Leaves usually cauline; sheaths usually smooth, sometimes scabridulous; ligules 1–6 mm, dorsal surfaces scabrous, apices truncate to rounded or acute, often lacerate to erose; blades 1.5–11.5 cm long, 1–6 mm wide, flat, becoming involute. Panicles 5–20 cm long, 0.4–6(8) cm wide, lanceolate to narrowly ovate, open to contracted, exserted from the upper sheaths at maturity, lowest node with 1–8 branches; branches scabrous to scabridulous, usually ascending, branching below midlength, the majority spikelet-bearing to the base, lower branches 2–5 cm; pedicels 0.5–7 mm. Spikelets lanceolate to narrowly ovate, green to yellowish green or yellow, tinged with purple. Glumes equal to subequal, 2–3.5 mm, scabrous over the midvein and sometimes also sparsely over the body, 1(3)-veined, acute to acuminate; callus hairs to 0.3(1) mm, sparse; lemmas 1.5–2.5 mm, smooth or scabridulous or warty, 5-veined, veins prominent throughout or only distally, apices acute, entire or the veins excurrent to about 0.2 mm, usually unawned, rarely awned from below the apices, awns to 0.5(2.7) mm, straight; paleas absent, or to 0.2 mm and thin; anthers 3, 0.7–1.8 mm. Caryopses 1–1.5 mm; endosperm solid. 2n = 42, 56.

Agrostis pallens grows on coastal sands and cliffs, in meadows, and in open, xeric woodlands to subalpine woodlands at 3500 m. It extends from British Columbia south into Baja California, Mexico, and east to western Montana and Utah. The relationship of the higher-elevation, more open-panicled plants to those of lower elevations merits further study.

18. Agrostis hallii Vasey
Hall’s Bent

Plants perennial; rhizomatous, rhizomes to 50 cm, not stolon-iferous. Culms 17–100 cm, erect. Leaves mostly cauline or somewhat basally concentrated; sheaths smooth; ligules 2.3–7 mm, dorsal surfaces scabrous, apices acute, usually lacerate; blades 6–20 cm long, 2–5 mm wide, flat. Panicles 7–22 cm long, 1.5–5.5(7) cm wide, lanceolate to narrowly ovate, more or less open to dense, lowest node with 2–15 branches; branches scabridulous, ascending to more or less appressed, mostly branching at or above midlength, some branching near the base, lower branches 1–5 cm; pedicels 0.5–6 mm. Spikelets lanceolate, yellow-green, often tinged with purple. Glumes equal to subequal, 2.5–4 mm, 1-veined, scabrous to scabridulous on the midvein, at least distally, sometimes also sparsely scabridulous over the back, acute to acuminate; callus hairs (0.8)1–2 mm, abundant, conspicuous; lemmas 2–3 mm, smooth, translucent to opaque, 5-veined, veins prominent at least distally, apices acute, entire or erose, sometimes toothed, teeth to about 0.2 mm, unawned; paleas absent, or to 0.2 mm and thin; anthers 3, 1.5–2.3 mm. Caryopses 1.5–2 mm. 2n = 42.

Agrostis hallii is primarily coastal, growing in open areas of oak and coniferous forests in Oregon and California.

19. Agrostis hooveri Swallen
Hoover’s Bent

Plants perennial; cespitose, not rhizomatous, not stoloniferous. Culms 30–80 cm, erect, usually with more than 3 nodes. Leaves mostly on the lower 1/2 of the culm; basal leaves withered by anthesis; lower leaf sheaths finely tomentose, the tomentum extending to below ground; upper leaf sheaths smooth; ligules 2.5–6 mm, dorsal surfaces scabridulous, apices acute to truncate, lacerate; blades 10–16 cm long, 0.5–1(2) mm wide, flat, becoming involute. Panicles (4)10–17 cm long, 2–5 cm wide, broadly lanceolate, usually open, exserted from the upper sheaths at maturity, lowest node with 1–8 branches; branches scabrous, generally ascending, mostly branching at about midlength, sometimes to near the base, lower branches 1.5–5 cm; pedicels 0.4–5 mm. Spikelets lanceolate, slightly purplish. Glumes equal to subequal, 1.8–3 mm, 1-veined, scabridulous on the veins, sometimes also on the body, acute; callus hairs to 0.3 mm, abundant; lemmas 1.5–2 mm, scabridulous to warty throughout or only on the veins, translucent to opaque, 5-veined, veins prominent distally, apices truncate, minutely toothed to about 0.2 mm, awned on the lower 1/3, awns to 2.5 mm, geniculate, persistent; paleas absent or minute; anthers 3, 1–1.5 mm, usually shed at anthesis. Caryopses 1–1.5 mm; endosperm liquid. 2n = unknown.

Agrostis hooveri is an uncommon species, endemic to dry, sandy soils, open chaparral, and oak woodlands of San Luis Obispo and Santa Barbara counties, California.

20. Agrostis howellii Scribn.
Howell’s Bent

Plants perennial; cespitose, not rhizomatous, not stoloniferous. Culms 40–80 cm, geniculate and decumbent at the base, sometimes rooting at the lower nodes, with 3–6 nodes. Leaves mostly cauline; basal leaves withered by anthesis; cauline leaves persisting; sheaths smooth or scabridulous; ligules (0.9)2.7–5 mm, dorsal surfaces scabrous, apices truncate to acute, erose to lacerate; blades 15–20 cm long, 3–5 mm wide, flat. Panicles 10–25 cm long, 3.5–11 cm wide, ovate, open and diffuse, bases usually exserted, rarely enclosed in the upper sheaths, lowest node with (1)2–6 branches; branches scabridulous, flexuous, spreading, spikelets usually only on the distal 1/2, lower branches 3–10 cm; pedicels 1.2–9.4 mm. Spikelets ovate to lanceolate, green, not or slightly tinged with purple. Glumes unequal, 2.3–3.5 mm, 1(3)-veined, veins scabridulous, acute to acuminate; callus hairs to 0.3 mm, abundant; lemmas 2.5–3 mm, usually smooth, sometimes scabridulous, translucent to opaque, 5-veined, veins prominent distally or obscure, apices acute to obtuse, lateral veins extending as 4 teeth to 0.5 mm, awned from the lower 1/3, awns 4–6 mm, geniculate; paleas absent or minute; anthers 3, 1–1.3 mm. Caryopses 1.2–1.6 mm; endosperm liquid. 2n = 28.

Agrostis howellii is a rare Washington and Oregon endemic, growing in shady woodlands and at the base of cliffs.

21. Agrostis variabilis Rydb.
Mountain Bent

Plants perennial; cespitose, rarely rhizomatous, rhizomes to 2 cm. Culms 5–30 cm, erect, sometimes geniculate at the base, with 2–5(7) nodes. Leaves mostly basal, forming dense tufts; sheaths smooth; ligules (0.7)1–2.8 mm, dorsal surfaces usually scabridulous, sometimes smooth, apices rounded to truncate, lacerate to erose; blades 3–7 cm long, 0.5–2 mm wide, flat, becoming folded or involute. Panicles (1)2.5–6 cm long, 0.3–1.2(2) cm wide, cylindric to lanceolate, usually dense, exserted from the upper sheaths at maturity, lowest node with 1–5 branches; branches usually scabridulous, sometimes smooth, ascending to erect, branching at or near the base and spikelet-bearing to the base, to branching in the distal 2/3, lower branches 0.5–1.5 cm; pedicels 0.4–2.8(4.3) mm. Spikelets ovate to lanceolate, greenish purple. Glumes subequal to equal, 1.8–2.5 mm, smooth, or scabrous on the keel and sometimes elsewhere, 1-veined, acute to acuminate; callus hairs to 0.2 mm, sparse to abundant; lemmas 1.5–2 mm, smooth, translucent, (3)5-veined, veins usually prominent distally, sometimes obscure through-out, apices acute, entire, usually unawned, rarely awned, awns to 1(2.8) mm, arising beyond the midpoint, usually not reaching the lemma apices; paleas to 0.2 mm, thin; anthers 3, 0.4–0.7(1) mm. Caryopses 1–1.3 mm; endosperm soft. 2n = 28.

Agrostis variabilis grows in alpine and subalpine meadows and forests and on talus slopes, at elevations up to 4000 m, from British Columbia and Alberta south to California and New Mexico. It can appear similar to dwarf forms of Podagrostis humilis, but differs from that species in not having paleas.

22. Agrostis blasdalei Hitchc.
Blasdale’s Bent

Plants perennial; forming dense, stiff clumps, not rhizomatous or stoloniferous. Culms 6–30 cm, decumbent to erect. Leaves forming a dense, bristly basal tuft; ligules 0.7–2.3 mm, dorsal surfaces scabridulous, apices truncate to obtuse, often erose, sometimes lacerate or ciliolate; blades 2–5 cm long, less than 1 mm wide, soon becoming tightly inrolled and rigid. Panicles 2–8 cm long, 0.2–0.6 cm wide, narrowly cylindric, spikelike, dense, occasionally interrupted near the base, the base often enclosed by the upper sheaths; branches to 2 cm, scabrous, strongly appressed, hidden by the spikelets; pedicels 0.5–7 mm. Spikelets lanceolate to narrowly ovate, greenish to purplish. Glumes 1.8–4 mm, often 3-veined, midveins scabrous to smooth, acute to acuminate; calluses glabrous; lemmas 1.5–2.5 mm, 5-veined, veins obscure or prominent distally, extending as teeth to 0.2 mm, unawned or awned from above midlength, awns to 1.2 mm, usually scarcely exceeding the lemma apices, straight; paleas to 0.3 mm, thin; anthers 3, 0.7–2 mm. Caryopses 1–1.5 mm; endosperm liquid. 2n = 42.

Agrostis blasdalei is a xerophytic species that is known only from Mendocino to Santa Cruz counties, California, where it grows on coastal cliffs and dunes and in shrublands. It hybridizes with A. densiflora.

23. Agrostis tolucensis Kunth

Plants perennial; cespitose. Culms (3.3)5.5–60 cm, erect, glabrous, with (2)3–4 nodes. Leaves mostly basal or evenly distributed; sheaths glabrous, scabridulous; ligules 2–6.2 mm, membranous, scabridulous dorsally, apices acute to more or less truncate, erose to lacerate; blades 4–19 cm long, 0.5–4 mm wide, involute or flat, scabrous or smooth over the veins. Panicles 1.5–14 cm long, 0.5–1.5 cm wide, lanceoloid, somewhat spikelike, dense to somewhat open, exserted at anthesis; branches appressed, shorter than 2 cm; pedicels 0.7–3(4.5) mm, scabrous. Spikelets purple to green, shiny. Glumes subequal, 2–3.5 mm, 1-veined, keeled, keels and back usually smooth, occasionally scabrous, apices acute, muticous; lower glumes wider than the upper glumes; calluses with 2 tufts of hair to 0.3 mm; lemmas 1.4–1.9 mm, glabrous, 5-veined, veins evident, apices truncate to acute, microdenticulate, teeth to about 0.1 mm, dorsally awned from midlength or below, awns 2–3.5 mm, exserted, twisted, geniculate, scabridulous; paleas 0.1–0.2 mm, hyaline, linear; anthers 3, 0.5–1 mm. Caryopses 0.7–1.2 mm; endosperm soft. 2n = 28.

Agrostis tolucensis grows in alpine meadows, usually in damp areas by lakes or streams. It is native from Mexico to Chile, Bolivia, and Argentina, growing in the Andes at 1800–4900 m. Its presence in the Flora region is dubious; two specimens in the S.M. Tracy herbarium, from Brewster and Brown counties in Texas, are listed in the Flora of Texas online database . Attempts to locate the specimens in 2005 were unsuccessful, suggesting the records may have been based upon misidentifications which have since been rectified.

24. Agrostis rossiae Vasey
Ross’ Bent

Plants annual. Culms 4–20 cm. Sheaths smooth, upper sheaths inflated; ligules (0.6)1–1.5 mm, dorsal surfaces scabrous, apices truncate to rounded, lacerate to erose-ciliolate; blades 1–2.5 cm long, 1–2 mm wide, flat or folded. Panicles 1.5–6 cm long, 0.4–2 cm wide, initially lanceo-late, becoming ovate and diffuse, bases sometimes enclosed in the upper sheaths; branches 1–3 cm, erect to spreading, scabrous; pedicels 0.5–6.3 mm. Spikelets ovate, green, slightly to strongly tinged with purple. Glumes equal, 2–2.5 mm, 1-veined, acuminate; lower glumes scabrous on the midvein; upper glumes smooth or scabrous on the midvein; callus hairs to 0.1 mm, sparse; lemmas 1.3–1.7 mm, scabrous, translucent to opaque, 5-veined, veins mostly obscure, apices truncate, entire, erose, or the veins excurrent to about 0.12 mm, unawned; paleas to 0.2 mm, thin; anthers 3, 0.5–0.9 mm, often retained at the apices of the caryopses. Caryopses 1.2–1.5 mm; endosperm semisoft. 2n = unknown.

Agrostis rossiae is a rare species, originally known only from alkaline soils near hot springs in Yellowstone National Park, Wyoming. Tercek et al. (2003) showed that somewhat morphologically similar plants of A. scabra found around hot springs in Yellowstone and Lassen Volcanic National Parks, and of A. pauzhetica Prob. found around hot springs on the Kamchatka Peninsula, Russia, are closely related to A. rossiae. They recommended, however, that the three be treated as separate species until more information has been obtained.

25. Agrostis hendersonii Hitchc.
Henderson’s Bent

Plants annual. Culms 6–70 cm, erect, with 2–5 nodes. Sheaths smooth; ligules 0.5–5 mm, usually scabridulous, dorsal sur-faces sometimes smooth, apices acute to obtuse, erose-lacerate, sometimes ciliolate; blades 1–4.5 cm long, 0.5–1(2) mm wide, flat or weakly involute. Panicles 1–5 cm long, 0.5–1.5 cm wide, cylindrical, spikelike, dense, sometimes interrupted near the base, usually well exserted from the upper sheaths; branches scabridulous, ascending to appressed, mostly hidden by the spikelets, lower branches 0.5–2.5 cm; pedicels 0.5–4(6.3) mm. Spikelets lanceolate, greenish to yellowish, tinged with purple. Glumes subequal, 5–7 mm, scabrous over the midvein, often sparsely scabridulous over the body, 1(3)-veined, apices narrowly acuminate to awn-tipped to 2 mm; callus hairs to 0.7 mm, abundant; lemmas 2.5–4 mm, scabridulous over the veins and sometimes over the body, opaque to translucent, 5-veined, veins prominent distally, apices acute, veins extended into 2 teeth, teeth 0.2–1.5 mm, awned from about midlength, awns (5)8–10 mm, more or less geniculate; paleas absent or to 0.9 mm; anthers 3, 0.4–0.7 mm. Caryopses 1.6–1.8 mm. 2n = 42.

Agrostis hendersonii is a rare species that grows below 600 m in clay or adobe, sometimes rocky, soils around the edges of vernal pools in Oregon and California.

Agrostis aristiglumis Swallen, known only from its type locality on the Point Reyes Peninsula, Marin County, California, is included here in A. hendersonii. It differs from A. hendersonii in having a palea up to 0.9 mm long, and a barely exserted panicle. The relationship of these to each other and to A. microphylla merits investigation. Their differences may be the result of the founder effect on inbreeding annuals.

26. Agrostis microphylla Steud.
Small-Leaf Bent

Plants annual. Culms 8–45 cm, erect. Leaves usually mostly cauline, sometimes mostly basal; sheaths glabrous or pub-escent; upper sheaths usually inflated; ligules 1.4–4.5 mm, dorsal surfaces scabridulous, apices truncate to acute, lacer-ate to erose; blades 3–15 cm long, 0.7–2.5 mm wide, flat, becoming involute, finely scabrous. Panicles 2–12 cm long, 0.4–2 cm wide, cylindrical, spikelike, dense, occasionally lobed or interrupted near the base, appearing bristly from the awns, usually exserted from the upper sheaths at maturity; branches 0.3–1.5 cm, scabrous to scab-ridulous, ascending to appressed, spikelet-bearing to the base and hidden by the spikelets; pedicels 0.3–3 mm. Spikelets lanceolate, greenish to yellowish, tinged with purple. Glumes equal to subequal, 2.5–5 mm, scabrous over the midvein and often scabridulous on the body, 1-veined, apices narrowly acuminate to awn-tipped, awns to 1.5 mm; callus hairs to 0.5(1) mm, usually dense; lemmas 1.5–2.3 mm, scabrous, translucent to opaque, 5-veined, veins prominent distally, apices acute, veins extended into 2(4) teeth, teeth 0.1–0.5 mm, awned from about midlength or above, awns 3.5–8 mm, geniculate; paleas absent, or to 0.2 mm and thin; anthers 3, 0.4–0.6 mm, often retained at the apices of the caryopses. Caryopses 0.9–1.3 mm; endosperm soft. 2n = 56.

Agrostis microphylla grows in thin, rocky soils, sandy areas, cliffs, vernal pools, and serpentine areas. It is a winter annual, flowering in late winter to spring, adapted to low-competition habitats with summer drought. It may be related to, or conspecific with, A. hendersonii.

Agrostis microphylla grows mostly along the Pacific coast from British Columbia to northern Baja California, Mexico. Reports of A. microphylla from the Humboldt Mountains, Nevada, reflect Vasey’s treatment of a specimen of A. exarata as the type of a new variety, A. microphylla var. major Vasey.

27. Agrostis elliottiana Schult.
Elliott’s Bent

Plants annual. Culms 5–45 cm, erect, sometimes geniculate at the base, with (3)4–9 nodes. Leaves mostly basal or cauline; basal leaves withered at anthesis; sheaths smooth or scabridulous; ligules (0.7) 1.5–3.5 mm, dorsal surfaces scabrous, apices acute, rounded, or truncate, lacerate; blades 0.5–4 cm long, 0.5–1 mm wide, flat, becoming involute. Panicles 3–20 cm long, (0.5)2–12 cm wide, widely ovate, ultimately open and diffuse, the whole panicle detaching after maturity, blowing about as a tumbleweed, bases usually exserted, sometimes enclosed by the upper sheaths at maturity, lowest node with 1–6 branches; branches scabridulous, capillary, branching beyond midlength, initially ascending, becoming laxly spreading, spikelets clustered near the tips, lower branches 2–8 cm; pedicels 0.3–7.5 mm; secondary panicles sometimes present in the leaf axils. Spikelets narrowly elliptic to lanceolate, yellowish purple to greenish purple. Glumes equal, 1.5–2.2 mm, 1-veined, scabrous on the midvein, margins scabrous distally, acute; callus hairs to 0.6 mm, dense; lemmas 1–2 mm, smooth or scabrous to warty, translucent, 5-veined, veins prominent, apices acute, entire or 2–5-toothed, teeth minute, to 0.8 mm, usually awned from just below the apices, sometimes unawned, awns 3–10 mm, flexuous, not geniculate, deciduous; paleas absent or minute; anthers 1, 0.1–0.2 mm, lobes widely separated by the connective, usually retained at the apices of the caryopses. Caryopses 1–1.4 mm; endosperm liquid. 2n = 28.

Agrostis elliottiana grows in fields and scrublands and along roadsides. It has a disjunct distribution, occurring in western North America in northern California and southern Arizona and New Mexico; in eastern North America from Kansas and Texas east to Pennsylvania and northern Florida; and in Yucatan, Mexico. Although it has been introduced elsewhere, notably in Maine, it is not known to have become established at those locations.

Agrostis elliottiana resembles A. scabra and A. hyemalis in its diffuse panicle, but differs in its flexible awn and single anther. Small Californian plants have sometimes been called A. exigua Thurb.; they are otherwise identical to A. elliottiana.

28. Agrostis nebulosa Boiss. & Reut.
Cloud Grass

Plants annual. Culms 10–75 cm, erect or geniculate, with 2–7 nodes. Leaves mostly cauline; sheaths scabrous; ligules 1–6 mm, dorsal surfaces scabrid-ulous, apices acute to rounded, erose to lacerate; blades 5–15 cm long, 1–4 mm wide, flat. Panicles 3–30 cm long, (2)5–20 cm wide, oblong to ovate, diffuse, usually over 1/2 the length of the culm, lowest node with (2)3–18 branches; branches scabrous, erect to spreading, lower branches 4–15 cm; pedicels (2.5)4–15 mm, much longer than the spikelets. Spikelets lanceolate, usually purplish, sometimes green to yellowish green. Glumes subequal, 1.3–2.1 mm, 1-veined, sparsely aculeolate on the veins, obtuse; calluses glabrous; lemmas 0.5–0.8 mm, transparent, thin, veins scarcely visible, smooth and glabrous or rarely hairy, apices truncate to rounded or acute, toothed or erose, usually unawned, rarely awned from near the base; paleas 0.4–0.7 mm, about as long as the lemmas and of similar texture; anthers 3, 1–1.4 mm. Caryopses 0.6–0.8 mm. 2n = 14.

Agrostis nebulosa is native to Spain and Portugal. It is cultivated as an ornamental and for dried flower arrangements, but occasional escapes have been found on roadsides, ditches, and in fields in widely scattered locations in the Flora region.