Plants perennial; cespitose from knotty bases or rhizomatous. Culms 10-350 cm, erect, terete, solitary or in small to large clumps. Leaves mostly cauline; sheaths open, smooth, sometimes striate; ligules membranous, ciliate, cilia longer than the membranous bases; blades flat or involute. Inflorescences terminal, usually exceeding the upper leaves, 3-70 cm, panicles of 1-75 spikelike branches attached to an elongate rachis; branches racemosely arranged, alternate, opposite, or whorled, appressed to strongly divergent, axes 3-sided, spikelets usually sessile on the 2 lower sides, usually divergent to strongly divergent; disarticulation beneath the glumes. Spikelets laterally compressed, with 1 floret. Glumes unequal, strongly keeled; lower glumes shorter than the florets, 1-veined; upper glumes usually longer than the florets, 1-6-veined; lemmas shorter than the paleas, 1-3-veined, midveins keeled, lateral veins usually obscure; paleas thin, papery, 2-veined, obscurely keeled; anthers 3; lodicules sometimes present, truncate, vascularized; styles 2, plumose. Caryopses rarely produced. x = 10. Name from the Greek spartine, a cord made from Spartium junceum, probably applied to Spartina because of the tough leaves.

Spartina is a genus of 15-17 species, most of which grow in moist to wet, saline habitats, both coastal and interior. Reproduction of all the species is almost entirely vegetative.

There are nine native and two introduced species in the Flora region, plus three hybrids, one of which is native, the other two being deliberate introductions. One of the introduced species, S. maritima, grows in both Europe and at a few locations in Africa; the African populations may also represent introductions.

On the eastern seaboard of North America, the native species of Spartina extend as far north as Nova Scotia, but the few species native to the western seaboard do not extend north of California. Two species, S. alterniflora and S. densiflora, have, however, become established as far north as Washington and now threaten the health of many coastal salt marshes and mud flats (see http://www.spartina.org/ or http://www.ecy.wa.gov/programs/sea/coast/plants/spartina.html). Spartina alterniflora has also spread across southeastern China, "choking estuaries, crowding out native grasses, and reducing feed and habitat for migratory birds" (Normile 2004).

Mobberley (1956), on whose work this treatment is based, described three groups within Spartina, but did not give them formal recognition. Most of the species in the Flora region belong to his third group, which he characterized as having hard culms, scabrous leaf margins, more or less divergent inflorescence branches, usually closely imbricate spikelets, and hispid keels on their glumes and lemmas. Spartina alterniflora and S. foliosa belong to Mobberley's second group, the species of which have rather thick, succulent culms, glabrous blades with smooth margins, and less closely imbricate spikelets than in the other two groups. Spartina spartinae is the only species of his first group to grow in the Flora region. Like other members of the group, it has hard, slender culms, numerous short, closely imbricate inflorescence branches, spikelets that are hispid or villous, at least on the keels of the glumes, and no rhizomes.

Reeder (pers. com. 2003) pointed out that some of the information in Mobberly (1956) has not been supported by subsequent work. In particular, Reeder and Singh (1967) reported that lodicules are present in at least three species (Spartina patens, S. pectinata, and S. spartinae) and several taxonomists have obtained different chromosome counts. Most of the chromosome counts reported by Mobberly were multiples of seven, which led to speculation that the genus belonged in the Pooideae, but those obtained by other workers have all been multiples of 10. In the descriptions, Mobberly's counts are listed in [square brackets]; those from other works are unbracketed. Sources of the other counts are given under the notes for Spartina and are included in the references listed below.

1.   Spartina spartinae (Trin.) Merr.
Gulf Cordgrass

Plants cespitose, not rhizomatous. Culms 40-200 cm, in large clumps, hard, usually glabrous, nodes frequently exposed. Sheaths mostly glabrous, throat glabrous, sometimes scabrous; ligules 1-2 mm; blades 1.5-4.5 mm wide, involute when fresh, abaxial surfaces glabrous, adaxial surfaces and margins scabrous. Panicles 6-70 cm, smoothly cylindrical in outline, with (6)15-75 branches, internodes shorter than the branches; branches 0.5-4(7) cm, lower branches often longer than those above, all branches tightly appressed, closely imbricate, with 10-60 spikelets. Spikelets 5-8(10) mm. Glumes glabrous or hispidulous, keels hispid; lower glumes 2-8 mm, acuminate; upper glumes 4-8(10) mm, acuminate to obtuse, keels hispid, lateral veins 1-2, if 2, these on either side of the keel; lemmas 5-6 mm, glabrous or hispidulous, keels hispid over the distal 2/3, apices usually acuminate or apiculate, rarely obtuse; anthers 3-5 mm, dark red to purple. 2n = 40 [28, 42].

Spartina spartinae grows from the Gulf coast through Mexico to Costa Rica in North America and, in South America, in Paraguay and northern Argentina. In the United States, it grows in sandy beaches, roadsides, ditches, wet meadows, and arid pastures near the coast, the most inland collection being 60 miles from the coast. In other parts of its range it sometimes grows well inland in saline soils where Pinus palustris (longleaf pine) is dominant or co-dominant.

2.   Spartina alterniflora Loisel.
Smooth Cordgrass, Spartine Alterniflore

Plants rhizomatous; rhizomes elongate, flaccid, white, scales inflated, not or only slightly imbricate. Culms to 250 cm tall, (0.3)5-15(20) mm thick, erect, solitary or in small clumps, succulent, glabrous, having an unpleasant, sulphurous odor when fresh. Sheaths mostly glabrous, throat glabrous or minutely pilose, lower sheaths often wrinkled; ligules 1-2 mm; blades to 60 cm long, 3-25 mm wide, lower blades shorter than those above, usually flat basally, becoming involute distally, abaxial surfaces glabrous, adaxial surfaces glabrous or sparsely pilose, margins usually smooth, sometimes slightly scabrous, apices attenuate. Panicles 10-40 cm, with 3-25 branches, often partially enclosed in the uppermost sheath; branches 5-15 cm, loosely appressed, not twisted, more or less equally subremote to moderately imbricate throughout the panicle, axes often prolonged beyond the distal spikelets, with 10-30 spikelets. Spikelets 8-14 mm, straight, usually divergent, more or less equally imbricate on all the branches. Glumes straight, sides usually glabrous, sometimes pilose near the base or appressed pubescent, hairs to 0.3 mm; lower glumes 4-10 mm, acute; upper glumes 8-14 mm, keels glabrous, lateral veins not present, apices acuminate to obtuse, occasionally apiculate; lemmas glabrous or sparsely pilose, apices usually acuminate; paleas slightly exceeding the lemmas, thin, papery, apices obtuse or rounded; anthers 3-6 mm. 2n = 62 [56, 70].

Spartina alterniflora is found on muddy banks, usually of the intertidal zone, in eastern North and South America, but it is not known from Central America. In addition, it has become established on the west coast of North America, England, southeastern France, and China. It hybridizes with S. maritima in Europe, with S. pectinata in Massachusetts, and with S. foliosa in California.

The rhizomes and scales of S. alterniflora have large air spaces, presumably an adaptation to the anaerobic soils of its usual habitat. Decaploid plants tend to be larger than octoploids, but they cannot be reliably distinguished without a chromosome count.

Spartina alterniflora is considered a serious threat to coastal ecosystems in Washington and California. It out-competes many of the native species in these habitats and frequently invades mud flats and channels, converting them to marshlands. Pure S. alterniflora grows within the lower elevational marsh zones in its native range but, in San Francisco Bay, its hybrids with S. foliosa grow both below and above the range of that species.

3.   Spartina foliosa Trin.
California Cordgrass

Plants occasionally streaked or tinged with purple, rhizomatous; rhizomes elongate, flaccid, whitish, scales inflated, not closely imbricate. Culms to 150 cm tall, to 10 mm thick, erect, terete, solitary or in small clumps, succulent, glabrous, often with adventitious roots from the lower nodes, having an unpleasant, sulphurous odor when fresh. Sheaths mostly glabrous, throats sparsely pilose, lower sheaths sometimes somewhat wrinkled; ligules 1-2 mm; blades 8-12 mm wide, flat to loosely involute, glabrous, margins usually smooth, sometimes slightly scabrous, apices acuminate. Panicles 12-25 cm, with 3-25 branches, smoothly cylindrical, often partially enclosed in the uppermost sheath; rachises twisted, glabrous; branches 2-8 cm, usually closely appressed and twisted, lower branches noticeably longer and less closely imbricate than the upper branches, all branches with axes rarely extending past the distal spikelets, with 8-30 spikelets. Spikelets 8-25 mm, usually appressed, often appearing twisted, those on the lower branches usually less closely imbricate than those on the upper branches. Glumes usually curved, sides and keels glabrous, scabrous, or hispid, apices acuminate to obtuse or rounded; lower glumes 6-12 mm; upper glumes 8-25 mm, 1-veined; lemmas glabrous or sparsely appressed pubescent on the sides, keels glabrous, apices obtuse, rounded or lobed; paleas slightly exceeding the lemmas, thin, papery, glabrous, apices usually rounded, rarely acuminate; anthers 3-6 mm. 2n = 60 [56].

Spartina foliosa grows in the intertidal zone from northern California to Baja California, Mexico. Populations in San Francisco Bay are threatened by various introduced species of Spartina. Of particular concern is S. alterniflora, which forms hybrids with S. foliosa that have a broader ecological amplitude than either parent. In California, S. foliosa is often confused with S. densiflora, which is also established in some regions, but S. foliosa differs from that species in being rhizomatous and having softer culms and wider leaf blades.

4.   Spartina maritima (Curtis) Fernald
Small Cordgrass

Plants rhizomatous; rhizomes with scales not inflated, not imbricate. Culms to 80 cm, relatively soft, solitary or in small clumps. Sheaths mostly glabrous, throat sometimes sparingly pilose, lower sheaths often wrinkled; ligules 0.2-0.6 mm; blades 6-12 cm long, 5-8 mm wide, loosely involute, disarticulating from the sheaths, abaxial surfaces glabrous, adaxial surfaces glabrous or sparsely pilose, margins smooth. Panicles 4-14 cm, with (1)2-3(7) branches; branches 2-11 cm, alternate, loosely appressed, not twisted, lower and upper branches more or less equally imbricate, with 5-30 spikelets. Spikelets 10-15 mm. Glumes straight, mostly appressed pubescent, only the margins glabrous; lower glumes 7-10 mm, narrow, acuminate, obtuse, or rounded; upper glumes 10-15 mm, acuminate (rarely obtuse); lemmas mostly appressed pubescent, margins and basal portion of the keels glabrous, apices acuminate; anthers 3-6.5 mm, well-filled, dehiscent at maturity. 2n = 60 [56].

Spartina maritima is a European species that has been reported as growing in Mississippi (Kartesz and Meacham 1999); the record has not been verified for this treatment. It also grows in Africa, possibly as an introduction.

5.   Spartina ×townsendii H. Groves & J. Groves
Townsend's Cordgrass

Plants rhizomatous; rhizomes whitish, scales not inflated, not closely imbricate. Culms to 150 cm, relatively hard, solitary or in small clumps. Sheaths mostly glabrous, throats pilose, lower sheaths often wrinkled; ligules 1-1.8 mm; blades 6-30 cm long, 4-12 mm wide, diverging 20-45° from the culms, flat proximally, involute distally, both surfaces glabrous, margins smooth. Panicles 15-25 cm, with 2-10 branches; branches 4-24 cm, loosely appressed, with 10-30 spikelets. Spikelets 16-22 mm. Glumes mostly appressed pubescent, margins glabrous or sparingly hispidulous; lower glumes 8-14 mm, linear, acuminate to obtuse; upper glumes 16-22 mm, acuminate to obtuse; lemmas mostly pubescent, keels glabrous near the base, margins glabrous throughout, apices obtuse to rounded or obscurely lobed; anthers 5-10 mm, poorly filled, indehiscent at maturity. 2n = 62,60+2.

Spartina ×townsendii is a sterile hybrid between the European S. maritima and the American S. alterniflora. It seems to have formed spontaneously at several locations in Europe, often taking over the areas formerly occupied by its progenitors. At some locations it has given rise to the fertile amphiploid S. anglica, from which it differs morphologically in its narrower, less divergent upper blades, shorter ligules, shorter, less hairy spikelets, and poorly filled, indehiscent anthers. Spartina ×townsendii has been used throughout the world for tideland reclamation because it is easy to establish, but it displaces native species.

6.   Spartina anglica C.E. Hubb.
English Cordgrass

Plants rhizomatous; rhizomes elongate, flaccid, thick, whitish, imbricate. Culms 30-130 cm, forming large clumps. Sheaths glabrous, rounded dorsally; ligules 2-3 mm; blades 10-46 cm long, 6-15 mm wide, persistent or deciduous, flat or involute, adaxial surfaces ridged, not scabrous, margins smooth or slightly scabrous, sharply pointed, blades of upper leaves strongly divergent. Panicles 12-40 cm, with 2-12, more or less equally spaced branches; branches 16-25 cm, erect or somewhat divergent, axes pubescent, extending up to 5 cm beyond the spikelets; disarticulation at the base of the glumes, spikelets falling intact at maturity. Spikelets 14-21 mm long, 2-3 mm wide, narrowly oblong, appressed, closely imbricate. Glumes straight, sides appressed pubescent, keels ciliate or hispid, acute; lower glumes 10-14 mm, 2/3-4/5 as long as the upper glumes, 1-veined; upper glumes exceeding the floret, 3-6-veined; lemmas shorter than the upper glumes, shortly appressed pubescent, 1-3-veined, acute; paleas a little longer than the lemmas; anthers 5-13 mm, well-filled, dehiscent at maturity. 2n = 122-124.

Spartina anglica is a naturally formed amphidiploid, derived from S. ×townsendii, that was first recognized as a separate species in 1968. It has been introduced (like S. ×townsendii) for reclamation of tidal mudflats. It differs from Spartina ×townsendii in its wider and more widely divergent upper blades, longer ligules, longer, more hairy spikelets, and longer, well-filled anthers.

7.   Spartina bakeri Merr.
Sand Cordgrass

Plants cespitose, bases knotty, not rhizomatous. Culms to 200 cm, in large, dense clumps, indurate, often branching from the lower nodes. Sheaths smooth to striate, glabrous; ligules 0.5-2 mm; blades 10-50 cm long, 3-7 mm wide, usually involute, rarely flat, abaxial surfaces glabrous, adaxial surfaces and margins scabrous, apices acuminate. Panicles 8-25 cm, usually shallowly sinuous or lobed in outline, with 3-16 branches; branches 2-6 cm, usually appressed, moderately imbricate, axes glabrous, sometimes somewhat scabrous on the angles, with 10-30 spikelets. Spikelets 6-9 mm. Glumes with hispid keels and hispidulous margins, apices acuminate; lower glumes 3-6 mm, to 2/3 as long as the upper glumes; upper glumes 6-9 mm, hispidulous, 3-4-veined, lateral veins 2-3, prominent, on 1 side of the keel; lemmas mostly glabrous, keels hispid, margins glabrous or hispid, apices acute to obtuse, sometimes obscurely lobed; anthers about 5 mm, well-filled, dehiscent at maturity. 2n = 40 [42].

Spartina bakeri grows on sandy maritime beaches and other salt water sites in the southeastern coastal states and on the shores of inland, freshwater lakes in Florida. Its inflorescence is similar to that of S. patens, but the branches of S. patens usually diverge from the rachises at maturity, whereas those of S. bakeri remain appressed. Spartina bakeri is distinct from most other species of Spartina in North America in forming dense clumps and in being able to grow in freshwater habitats.

8.   Spartina cynosuroides (L.) Roth
Big Cordgrass

Plants strongly rhizomatous; rhizomes elongate, purplish-brown or tan, scales closely imbricate. Culms 100-350 cm tall, 1-2 cm thick, hard, solitary or few together. Sheaths smooth to striate, mostly glabrous, throats often densely pilose, lower sheaths often wrinkled; ligules 1-3 mm; blades 6-20 mm wide, flat or involute, glabrous on both surfaces, margins strongly scabrous, apices acuminate, second blade below the panicles 5-15 mm wide, usually flat. Panicles 15-40 cm, not smooth in outline, with 5-67 branches; branches 6-15 cm, usually spreading, with 10-70 spikelets. Spikelets 9-14 mm. Glumes with hispid keels and hispidulous margins; lower glumes 3-7 mm, from less than 1/2 as long as to 2/3 as long as the adjacent lemmas, linear, acute; upper glumes 9-14 mm, usually more than twice as long as the lower glumes, exceeding the florets, mostly glabrous or hispidulous, keels scabrous or hispid, trichomes to 0.3 mm, 2 lateral veins prominent, 1 on each side of the keel, usually hispid, apices unawned or awned, the awns to 2 mm; lemmas glabrous or hispidulous, sometimes glabrous proximally and hispidulous distally, apices obtuse to rounded, sometimes shallowly bilobed; anthers 4-6 mm, well-filled, dehiscent. 2n = 40 [28, 42].

Spartina cynosuroides grows in brackish estuaries, tidal lagoons and bays, and in maritime habitats bordering the strand and intertidal zones. It grows primarily on the eastern and Gulf coasts of the United States, but has also been found in Michigan, possibly introduced by shipping. Reports from South Dakota are based on a misidentification.

9.   Spartina densiflora Brongn.
Densely-Flowered Cordgrass

Plants cespitose, rarely rhizomatous; rhizomes, when present, short, to 10 mm thick. Culms 27-150 cm, forming large clumps, indurate, usually with short extravaginal shoots appressed to the culms. Sheaths glabrous, lower sheaths smooth, indurate and shining, upper sheaths dull and somewhat striate; ligules 1-2 mm; blades 12-43 cm long, 3-8 mm wide, involute when fresh, abaxial surfaces glabrous, adaxial surfaces and margins scabrous, apices acuminate. Panicles 10-30 cm long, 4-8 mm wide, sinuous in outline, often twisted, with 2-15 branches; branches 1-11 cm long, longer branches narrower than the shorter branches, all branches tightly appressed, moderately imbricate, axes not prolonged beyond the distal spikelets, with 10-30 spikelets. Spikelets 8-14 mm. Glumes glabrous or sparsely hispidulous, keels hispidulous, margins sparsely hispidulous; lower glumes 4-7 mm, usually obtuse; upper glumes 8-14 mm, 1-veined, usually acuminate; lemmas minutely hispidulous, keels glabrous proximally, hispidulous distally, apices acuminate to obtuse; paleas acuminate, keels glabrous basally, hispidulous distally; anthers 3-5 mm. 2n = 60.

Spartina densiflora is native to South America, where it grows in coastal marshes and at inland sites. It was introduced to Humboldt Bay, Humboldt County, California, possibly during the nineteenth century. It is now established there and in several locations around San Francisco Bay and in Washington, Oregon, and Texas, as well as the Mediterranean coast of Europe. In California, it has often been mistaken for S. foliosa, from which it differs in its indurate culms, narrow, inrolled leaves, and cespitose growth habit and tendency to grow among Salicornia in the upper intertidal zone or in open mud.

The chromosome count of 2n = 60 was obtained by Gerish (1979), who reported it for Spartina foliosa, but Spicher and Josselyn (1985) demonstrated that the plants he worked with were almost certainly S. densiflora, a species that hitherto had been misidentified as the native S. foliosa. In 2008, Ayres et al. (2008) and Fortune et al. (2008) reported that S. densiflora has 2n = 70.

10.   Spartina gracilis Trin.

Alkali Cordgrass

Plants strongly rhizomatous; rhizomes elongate, 1.5-5 mm thick, whitish, scales not inflated, closely imbricate. Culms 40-100 cm tall, 2-3.5 mm thick, usually solitary, erect, terete, indurate, glabrous. Sheaths smooth or striate, mostly or completely glabrous, throats occasionally ciliate; ligules 0.5-1 mm; blades 6-30 cm long, 2.5-8 mm wide, flat, becoming involute, abaxial surfaces glabrous, adaxial surfaces scabrous, margins scabrous. Panicles 8-25 cm, not smooth in outline, with 3-12 branches; branches 1.5-8 cm, alternate, differing only slightly in length and spacing within a panicle, usually appressed, rarely spreading, with 10-30 spikelets. Spikelets 6-11 mm, ovate to lanceolate. Glumes with glabrous or sparingly hispidulous margins, apices acute or mucronate; lower glumes 3-7 mm, sides narrow, glabrous or sparsely pubescent, keels glabrous or strigose; upper glumes 6-10 mm, usually equaling the florets, keels strigose, hairs 0.2-0.5 mm, lateral veins 2, inconspicuous, both on the same side of the keel; lemmas glabrous or sparsely hirsute, keels hirsute, at least distally, hairs 0.3-1 mm, margins sparsely hairy, apices obtuse to rounded, sometimes obscurely lobed; paleas sparsely hispid distally, obtuse to slightly rounded; anthers 2.5-5 mm, well-filled, dehiscent at maturity. 2n = 40 [42].

Spartina gracilis is found on the margins of alkaline lakes and along stream margins and river bottoms. Its range extends from the southern portion of the Northwest Territories, Canada, to central Mexico.

11.   Spartina patens (Aiton) Muhl.
Saltmeadow Cordgrass, Spartine Étalée

Plants strongly rhizomatous; rhizomes elongate, 1-6 mm thick, whitish, scales not imbricate. Culms 15-150 cm tall, 1-6 mm thick, usually solitary, indurate. Sheaths glabrous or mostly glabrous, throats occasionally short-pilose; ligules about 0.5(1) mm; blades 10-50 cm long, 0.5-4(7) mm wide, involute when fresh, abaxial surfaces glabrous, adaxial surfaces scabrous, margins strongly scabrous; blade of the second leaf below the panicles 4-40 cm long, 0.5-3(7) mm wide. Panicles 3-15 cm, not smooth in outline even if the branches appressed, with 2-15 branches; branches 1-7 cm, alternate, differing only slightly in length and spacing within a panicle, appressed to strongly divergent, with 10-30 spikelets. Spikelets 7-12 mm, linear lanceolate to ovate lanceolate. Glumes glabrous or sparsely hispidulous on the sides, keels scabrous to hispidulous, trichomes (1) 1.5-2.5 mm, apices acuminate; lower glumes 3-8 mm, linear; upper glumes 7-12 mm, with 2 lateral veins, these on the same side of the keel, usually hispid, apices acuminate, acute, or obtuse; lemmas mostly glabrous or sparsely hispidulous, keels hispid distally, apices obtuse, rounded, or obscurely lobed; anthers 3-5 mm, well-filled, indehiscent. 2n = 40 [28, 35, 42, 56].

Spartina patens grows in coastal salt and brackish waters. It is native to the east coast of North and Central America, extending through the Caribbean Islands to the north coast of South America, but is now established at scattered locations on the west coast of Canada and the United States. On the east coast, it is usually one of the dominant components of coastal salt marshes, frequently extending from the dry, sandy beach above the intertidal zone well up into the drier portions of the marshes. The older inland collections are from areas associated with brine deposits or saline soils, but there is some indication that the species range is increasing inland because of the use of salt to de-ice roads in winter.

The inflorescence of Spartina patens is similar to that of S. bakeri when young, but its inflorescence branches usually diverge at maturity, whereas those of S. bakeri remain appressed.

Spartina patens is probably one of the parents of S. ×caespitosa, S. pectinata being the other. Unlike S. ×caespitosa, S. patens grows in both disturbed and undisturbed habitats.

12.   Spartina ×caespitosa A.A. Eaton
Mixed Cordgrass

Plants rhizomatous or not; rhizomes, when present, thick, usually purplish-brown, scales closely imbricate. Culms to 120 cm tall, 1-3 mm thick, indurate, solitary or in small, dense clumps. Sheaths mostly glabrous, throats glabrous or short-pilose; ligules 0.5-1 mm; blades 8-56 cm long, 2-6(7) mm wide, usually involute, abaxial surfaces glabrous, adaxial surfaces glabrous or scabrous, margins strongly scabrous, blade of the second leaf below the panicles 8-56 cm long, 2-5(7) mm wide. Panicles 9-20 cm, not smoothly cylindrical, with 3-9 branches; branches 3-9 cm, appressed or spreading, with 20-50 spikelets. Spikelets 10-17 mm, lanceolate to ovate-lanceolate. Glumes glabrous or sparsely hispidulous, keels glabrous, hispid in whole or in part, or ciliate; lower glumes 4-9 mm, acuminate or awned; upper glumes 10-17 mm, exceeding the florets, keels hispid, lateral veins prominent, 1 on each side of the keel or 2-3 on 1 side of the keel, apices acuminate or awned; lemmas glabrous or sparsely hispidulous, apices obtuse, rounded, obscurely lobed, or apiculate; anthers 3-6 mm, poorly filled, indehiscent. 2n = [42].

Spartina ×caespitosa is found in disturbed areas of the drier portions of salt and brackish marshes, at some distance above the intertidal zone. It occurs sporadically along the coast from Maine to Maryland, a region where its putative parents, S. pectinata and S. patens, are sympatric. None of the populations Mobberley (1956) examined was growing in undisturbed land.

Mobberley's (1956) investigations led him to conclude that the populations of S. ×caespitosa are polythetic in origin. Part of the evidence for his conclusion was the variability he observed. It is this variability that makes it necessary to bring out the hybrid at several locations in the key. Its distribution is, however, very limited, a fact that may be more useful for identification than any of the morphological characteristics examined.c

13.   Spartina pectinata Link
Prairie Cordgrass, Spartine Pectinée

Plants strongly rhizomatous; rhizomes elongate, (2)3-8 mm thick, purplish-brown or light brown (drying white), scales closely imbricate. Culms to 250 cm tall, 2.5-11 mm thick, solitary or in small clumps, indurate. Sheaths mostly glabrous, throats often pilose; ligules 1-3 mm; blades 20-96 cm long, 5-15 mm wide, flat when fresh, becoming involute when dry, glabrous on both surfaces, margins strongly scabrous, blade of the second leaf below the panicles 32-96 cm long, 5-14 mm wide, usually involute. Panicles 10-50 cm, not smooth in outline, with 5-50 branches; branches 1.5-15 cm, appressed to somewhat spreading, with 10-80 spikelets. Spikelets 10-25 mm. Glumes shortly awned, glabrous or sparsely hispidulous; lower glumes 5-10 mm, from 3/4 as long as to equaling the adjacent lemmas, keels hispid, apices awned; upper glumes 10-25 mm (including the awn), exceeding the florets, glabrous or sparsely hispid, keels scabrous to hispid, trichomes about 0.3 mm, lateral veins usually glabrous (rarely hispid), on either side of, and close to, the keels, apices awned, awns 3-8 mm; lemmas glabrous, keels pectinate distally, apices bilobed, lobes 0.2-0.9 mm; anthers 4-6 mm, well-filled, dehiscent. 2n = 40, 40+1, 80 [42, 70, 84].

Spartina pectinata is native to Canada and the United States, but it has been introduced at scattered locations on other continents. On the Atlantic coast, it grows in marshes, sloughs, and flood plains, being a common constituent of ice-scoured zones of the northeast and growing equally well in salt and fresh water habitats. In western North America, it grows in both wet and dry soils, including dry prairie habitats and along roads and railroads.

Spartina pectinata is thought to be one of the parents of S. ×caespitosa, the other parent being S. patens.