Plants perennial; often cespitose, usually rhizomatous. Culms 10-210 cm, unbranched or branched, more or less smooth, nodes 1-8. Sheaths open, smooth or scabrous; auricles absent; ligules membranous, usually truncate to obtuse, sometimes acute, entire or lacerate, lacerations often obscuring the shapes; blades flat to involute, smooth or scabrous, rarely with hairs. Inflorescences panicles, open or contracted, sometimes spikelike; branches appressed to more or less drooping, some branches longer than 1 cm. Spikelets pedicellate, weakly laterally compressed, with 1(2) florets; rachillas prolonged beyond the base of the distal floret(s), usually hairy; disarticulation above the glumes. Glumes membranous, subequal, equal to, or longer than the lemmas, rounded or keeled, backs smooth or scabrous, rarely long-scabrous with bent projections, veins obscure to prominent, apices acute to acuminate, rarely awn-tipped or attenuate; lower glumes 1(3)-veined; upper glumes 3-veined; calluses hairy, hairs 0.2-6.5 mm, sparse to abundant; lemmas 3(5)-veined, smooth or scabrous, apices usually tapering into 4 teeth, awned; awns arising from near the base to near the apices, straight or bent, sometimes delicate and indistinct from the callus hairs, sometimes exserted beyond the lemma margins; paleas well developed, almost as long as to slightly longer than the lemmas, thin, 2-veined; anthers 3, sometimes sterile. Caryopses shorter than the lemmas, concealed at maturity, oblong, usually glabrous, x = 7.
Conn., N.J., N.Y., Wash., Va., Del., Oreg., Wis., Colo., D.C, Utah, W.Va., Pacific Islands (Hawaii), Kans., N.Dak., Nebr., S.Dak., Mass., Maine, N.H., R.I., Vt., Wyo., N.Mex., La., N.C., Tenn., S.C., Pa., Ind., Ky., Calif., Nev., Iowa, Mont., Alaska, Ala., Ariz., Idaho, Ill., Md., Mich., Minn., Ohio, Ark., Ga., Alta., B.C., Greenland, Man., N.B., Nfld. and Labr., N.S., N.W.T., Nunavut, Ont., P.E.I., Que., Sask., Yukon, Mo.
Calamagrostis grows in cool-temperate regions and is especially diverse in mountainous regions. Its species grow in both moist and xeric habitats. There are about 100 species of Calamagrostis, if Deyeuxia Clarion ex P. Beauv. and Lachnagrostis are recognized as distinct from Calamagrostis. The latter two genera are often considered to be restricted to the Southern Hemisphere (Edgar 1995; Jacobs 2001). According to the criteria used by Phillips and Chen (2003) to distinguish Calamagrostis and Deyeuxia, most North American species of Calamagrostis fit within Deyeuxia. There has been insufficient time to evaluate the merits of their recommendation, adoption of which would require many new combinations.
Twenty-five species of Calamagrostis grow in the Flora region; one, C. epigejos, is introduced. Some species of Calamagrostis are rangeland forage grasses, but most occur too sparsely to be important for livestock. Agriculture Canada in Alberta experimented with cultivation of some western species during the 1960s and 1970s.
This treatment includes one cultivar, Calamagrostis ×acutiflora 'Karl Foerster', that is becoming increasingly popular in horticulture. A cultivar of C. canadensis has been registered for use in revegetation in arctic Alaska.
Interspecific hybridization is common; vivipary and agamospermy also occur in some species. Interspecific hybridization, polyploidy, and apomixis contribute to the taxonomic difficulty of the genus.
Some species of Calamagrostis are of interest because of their restricted distributions. These include: C. howellii (Columbia Gorge in Washington and Oregon); C. tweedyi (Washington, Oregon, and Montana); C. tacomensis (Washington and Oregon); C. ophitidis, C. foliosa, C. muiriana, and C. bolanderi (California); C. breweri (California and Oregon); and C. cainii (North Carolina and Tennessee). An incomplete draft treatment of this genus was prepared by Craig W. Greene in 1993, with minor revisions made until 1999. After Greene's death in 2003, completion of the treatment was taken up by Marr and Hebda. The taxa recognized here essentially follow Greene's concepts, with the following exceptions: Calamagrostis breweri sensu Greene (1993) has been split into C. muiriana and C. breweri sensu Wilson and Gray (2002); C. tacomensis is recognized as a species distinct from C. sesquiflora; and C. purpurascens var. laricina Louis-Marie and C. striata subsp. borealis (C. Laest.) Á. Löve & D. Love are not recognized. Descriptions of eastern North American taxa are largely based on Greene's (1980) observations. Northwestern North American taxa are described on the basis of Marr and Hebda's data and field experience. Other western United States taxa were also examined as herbarium specimens; their descriptions include observations by Marr and Hebda. Greene's key was rewritten to conform with the new data.
There is a high degree of misidentification of taxa within this genus (30% for some species in some herbaria), and species distributions should be taken as a guide only. Much more field collecting is needed for several of the taxa in order to verify their distributions, especially near the limits of their ranges. Calamagrostis is sometimes confused with Agrostis; there is no single character that distinguishes all species of Calamagrostis from those of Agrostis. In general, Calamagrostis has larger plants with larger, more substantial lemmas and paleas than Agrostis, and tends to occupy wetter habitats.
Measurements of the rachilla and callus hairs reflect the longest hairs present. Panicle widths refer to pressed specimens.The following key will enable typical specimens to be identified readily, but atypical specimens are common. For this reason, most leads require observation of a combination of characters, notably awn length, length of callus hairs relative to the lemma, glume length and scabrosity, panicle size, and leaf width.
Harmon, P.J. 1981. The vascular flora of the ridge top of North Fork Mountain, Grant and Pendleton counties, West Virginia. Master's thesis, Southern Illinois University, Carbondale, Illinois, U.S.A. 434 pp.
Hitchcock, C.L., A. Cronquist, and M. Ownbey. 1969. Vascular Plants of the Pacific Northwest. Part 1: Vascular Cryptogams, Gymnosperms, and Monocotyledons. University of Washington Press, Seattle, Washington, U.S.A. 914 pp.
Reznicek, A.A. and E.J. Judziewicz. 1996. A new hybrid species, xCalammophila don-hensonii (Ammophila brcviligulata x Calamagrostis canadensis, Poaceae) from Grand Island, Michigan. Michigan Bot. 35:35-40
|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 10x; 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|
|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|
|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|
|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|
|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|
|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|
|11||Blades 0.2-1.7 mm wide; panicles (1.5)1.9-8.5 cm long; callus hairs sparse.||> 12|
|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|
|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|
|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|
|14||Culms 10-55(60) cm tall; panicles open; blades (1)1.5-3(4) mm wide.||> 15|
|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|
|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|
|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 ×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|
|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|
|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|
|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|
|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|
|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|