9.01 GLYCERIA R. Br.
Mary E. Barkworth
Laurel K. Anderton

Plants usually perennial, rarely annual; rhizomatous. Culms (10)20–250 cm, erect or decumbent, freely rooting at the lower nodes, not cormous based. Sheaths closed for at least 3/4 their length, often almost entirely closed; ligules scarious, erose to lacerate; blades flat or folded. Inflorescences terminal, usually panicles, sometimes racemes in depauperate specimens, branches appressed to divergent or reflexed. Spikelets cylindrical and terete or oval and laterally compressed, with 2–16 florets, terminal floret in each spikelet sterile, reduced; disarticulation above the glumes, below the florets. Glumes much smaller than to equaling the adjacent lemmas, 1-veined, obtuse or acute, often erose; lower glumes 0.3–4.5 mm; upper glumes 0.6–7 mm; calluses glabrous; lemmas membranous to thinly coriaceous, rounded over the back, smooth or scabrous, glabrous or hairy, hairs to about 0.1 mm, 5–11-veined, veins usually evident, often prominent and ridged, not or scarcely converging distally, apical margins hyaline, sometimes with a purplish band below the hyaline portion, apices acute to rounded or truncate, entire, erose, or irregularly lobed, unawned; paleas from shorter than to longer than the lemmas, keeled, keels sometimes winged; lodicules thick, sometimes connate, not winged; anthers (1)2–3; ovaries glabrous; styles 2-branched, branches divergent to recurved, plumose distally. x = 10. Name from the Greek glukeros, ‘sweet’, the caryopses of the type species being sweet.

Glyceria includes approximately 35 species, all of which grow in wet areas. All but five species are native to the Northern Hemisphere. The genus is represented in the Flora region by 13 native and 3 introduced species, as well as 3 named hybrids. One additional European species, G. notata, is included in this treatment because it has been reported to be present in the region.

All native species of Glyceria are palatable to livestock. They are rarely sufficiently abundant to be important forage species. Some grow in areas that are soon degraded by grazing. Glyceria maxima can cause cyanide poisoning in cattle. Species in sects. Striatae and Hydropoa have potential as ornamentals.

Glyceria resembles Puccinellia in the structure of its spikelets and its preference for wet habitats; it differs in its inability to tolerate highly alkaline soils, and its usually more flexuous panicle branches, closed leaf sheaths, and single-veined upper glumes. Some species are apt to be confused with Torreyochloa pallida, another species associated with wet habitats but one that, like Puccinellia, has open leaf sheaths.

Glyceria includes several species that appear to intergrade. In some cases, the distinctions between such taxa are more evident in the field, particularly when they are sympatric. Recognition of such taxa at the specific level is merited unless it can be shown that all the distinctions between them are inherited as a group.

The three named North American hybrids are Glyceria ×gatineauensis Bowden, G. ×ottawensis Bowden, and G. ×occidentalis (Piper) J.C. Nelson. The first two were named as hybrids; they are not included in the key and are mentioned only briefly in the descriptions. Glyceria ×occidentalis has hitherto been treated as a species. Studies finished shortly before completion of this volume indicate that it, too, consists of hybrids (Whipple et al. [in press]). It is included in the key and provided with a full description.

Culm thickness is measured near midlength of the basal internode; it does not include leaf sheaths. Unless otherwise stated, ligule measurements reflect both the basal and upper leaves. Ligules of the basal leaves are usually shorter than, but similar in shape and texture to, those of the upper leaves. The number of spikelets on a branch is counted on the longest primary branches, and includes all the spikelets on the secondary (and higher order) branches of the primary branch. Pedicel lengths are measured for lateral spikelets on a branch, not the terminal spikelet. Lemma characteristics are based on the lowest lemmas of most spikelets in a panicle. There is often, unfortunately, considerable variation within a panicle.

SELECTED REFERENCES Anderson, J.E. and A.A. Reznicek. 1994. Glyceria maxima (Poaceae) in New England. Rhodora 96:97–101; Borrill, M. 1955. Breeding systems and compatibility in Glyceria. Nature 175:561–563; Bowden, W.M. 1960. Chromosome numbers and taxonomic notes on northern grasses: III. Festuceae. Canad. J. Bot. 38:117–131; Chester, E.W., B.E. Wofford, H.R. DeSelm, and A.M. Evans. 1993. Atlas of Tennessee Vascular Plants, vol. 1. Austin Peay State University Miscellaneous Publication No. 9. The Center for Field Biology, Austin Peay State University, Clarksville, Tennessee, U.S.A. 118 pp.; Church, G.L. 1949. Cytotaxonomic study of Glyceria and Puccinellia. Amer. J. Bot. 36:155–165; Conert, H.J. 1992. Glyceria. Pp. 440–457 in G. Hegi. Illustrierte Flora von Mitteleuropa, ed. 3. Band I, Teil 3, Lieferung 6 (pp. 401–480). Verlag Paul Parey, Berlin and Hamburg, Germany; Dore, W.G. and J. McNeill. 1980. Grasses of Ontario. Research Branch, Agriculture Canada Monograph No. 26. Canadian Government Publishing Centre, Hull, Québec, Canada. 568 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.; Komarov, V.L. 1963. Genus 176. Glyceria R. Br. Pp. 356–365 in R.Yu. Rozhevits [R.J. Roshevitz] and B.K. Shishkin [Schischkin] (eds.). Flora of the U.S.S.R., vol. 2, trans. N. Landau (series ed. V.L. Komarov). Published for the National Science Foundation and the Smithsonian Institution, Washington, D.C. by the Israel Program for Scientific Translations, Jerusalem, Israel. 622 pp. [English translation of Flora SSSR, vol. II. 1934. Botanicheskii Institut Im. V.L. Komarova, Akademiya Nauk, Leningrad, Russia. 778 pp.]; Koyama, T. 1987. Grasses of Japan and Its Neighboring Regions: An Identification Manual. Kodansha, Ltd., Tokyo, Japan. 370 pp.; Scoggan, H. 1978. Flora of Canada, part 2: Pteridophyta, Gymnosperms, Monocotyledoneae. National Museum of Natural Sciences Publications in Botany No. 72. National Museums of Canada, Ottawa, Ontario, Canada. 545 pp.; Voss, E.G. 1972. Michigan Flora: A Guide to the Identification and Occurrence of the Native and Naturalized Seed-Plants of the State, part 1. University of Michigan, Ann Arbor, Michigan, U.S.A. 488 pp.; Whipple, I.G., B.S. Bushman, and M.E. Barkworth. [in press]. Glyceria in North America.

 

For an interactive dichotomous key, click here; for an interactive, multientry key, click here.

 

1. Spikelets laterally compressed, lengths 1–4 times widths, oval in side view; paleal keels not winged (sects. Hydropoa and Striatae) ... 2
1. Spikelets cylindrical and terete, except at anthesis when slightly laterally compressed, lengths more than 5 times widths, rectangular in side view; paleal keels usually winged distally (sect. Glyceria) ... 11
2. Upper glumes 2.5–5 mm long, longer than wide ... 3
2. Upper glumes 0.6–3.7 mm long, if longer than 3 mm, then shorter than wide ... 4
3. Blades 3–7 mm wide; culms 2.5–4 mm thick, 60–90 cm tall; anthers 0.7–1.2 mm long ... G. alnasteretum
3. Blades 6–20 mm wide; culms 6–12 mm thick, 60–250 cm tall; anthers (1)1.2–2 mm long ... G. maxima
4. Panicles ovoid to linear; panicle branches appressed to strongly ascending; ligules of the upper leaves 0.5–0.9 mm long ... 5
4. Panicles pyramidal; panicle branches strongly divergent or drooping; ligules of the upper leaves 1–7 mm long ... 6
5. Panicles 5–15 cm long, 2.5–6 cm wide, ovoid, erect ... G. obtusa
5. Panicles 15–25 cm long, 0.8–1.5 cm wide, linear, nodding ... G. melicaria
6. Lemma apices almost flat; anthers 3; veins of 1 or both glumes in each spikelet usually extending to the apices ... G. grandis
6. Lemma apices prow-shaped; anthers 2; veins of both glumes terminating below the apices ... 7
7. Glumes tapering from below midlength to the narrowly acute (< 45°) apices; lemma lengths more than twice widths ... G. nubigena
7. Glumes narrowing from midlength or above to the acute (> 45°) or rounded apices; lemma lengths less than twice widths ... 8
8. Spikelets (2.5)3–5 mm wide; lemma veins evident but not raised distally; palea lengths 1.5–1.8 times widths ... G. canadensis
8. Spikelets 1.2–2.9 mm wide; lemma veins distinctly raised throughout; palea lengths 1.5–3.5 times widths ... 9
9. Lemmas 2.5–3.5 mm long; glume lengths about 3 times widths, glume apices broadly acute; lower glumes 1.5–2 mm long; upper glumes 2–2.6 mm long ... G. pulchella
9. Lemmas 1.2–2.2 mm long; glume lengths up to twice widths, glume apices rounded or acute; lower glumes 0.5–1.5 mm long; upper glumes 0.6–1.5 mm long ... 10
10. Blades 2–6 mm wide; anthers 0.2–0.6 mm long; culms 1.5–3.5 mm thick ... G. striata
10. Blades 6–15 mm wide; anthers 0.5–0.8 mm long; culms 2.5–8 mm thick ... G. elata
11. Lemmas tapering from near midlength to the acuminate or narrowly acute apices; paleas exceeding the lemmas by 0.7–3 mm; palea apices often appearing bifid, the teeth 0.4–1
mm long 13. G. acutiflora
11. Lemmas not tapered or tapering only in the distal 1/4, apices truncate, rounded, or acute; paleas shorter or to 1(1.5) mm longer than the lemmas; palea apices not or shortly bifid, the teeth to 0.5 mm long ... 12
12. Lemma apices with 1 strongly developed lobe on 1 or both sides, entire to crenulate between the lobes; blades 3–12 cm long; primary panicle branches 1.5–9.5 cm long ... G. declinata
12. Lemma apices not or more or less evenly lobed; blades 5–30 cm long; primary panicle branches 3–18 cm long ... 13
13. Lemmas 5–8 mm long ... 14
13. Lemmas 2.4–5 mm long ... 15
14. Anthers 0.6–1.6 mm long; lemma apices usually slightly lobed or irregularly crenate ... G. ×occidentalis (in part)
14. Anthers 1.5–3 mm long; lemma apices usually entire ... G. fluitans
15. Lemmas usually smooth between the veins, if scabridulous the prickles between the veins smaller than those over the veins ... 16
15. Lemmas scabridulous or hispidulous between the veins, the prickles between the veins similar in size to those over the veins ... 18
16. Lemmas usually acute, sometimes obtuse, entire or almost so; adaxial surfaces of the midcauline blades usually densely papillose, glabrous ... G. borealis
16. Lemmas truncate to obtuse, crenate; adaxial surfaces of the midcauline blades rarely densely papillose, sometimes sparsely hairy ... 17
17. Culms 73–182 cm tall; pedicels 0.7–1.7 mm ... G. septentrionalis (in part)
17. Culms 25–80 cm tall; pedicels 1–6 mm ... G. notata
18. Lemma apices acute ... 19
18. Lemma apices truncate to obtuse ... 20
19. Lemmas 2.4–4.8 mm long; pedicels 0.7–1.7 mm long; plants from east of the Rocky Mountains ... G. septentrionalis (in part)
19. Lemmas 4.5–5.9 mm long; pedicels 1.5–8 mm long; plants from west of the Rocky Mountains ... G. ×occidentalis (in part)
20. Pedicels 0.7–1.7 mm long; anthers 0.5–1.8 mm long; plants from east of the Rocky Mountains ... G. septentrionalis (in part)
20. Pedicels 2–5 mm long; anthers 0.3–0.9 mm long; plants from British Columbia and the Pacific states ... G. leptostachya

 

Glyceria sect. Hydropoa (Dumort.) Dumort.

Plants perennial. Sheaths not or only slightly compressed, midvein sometimes conspicuous distally. Panicles 12–30 cm wide, usually open; branches divergent to strongly divergent and drooping; pedicels 0.8–15 mm. Spikelets oval in side view, lengths 1–4 times widths, somewhat laterally compressed, usually not appressed to the panicle branches. Lemmas with apices acute to rounded or truncate, more or less flat to slightly prow-shaped; paleas keeled, keels not winged, truncate to notched between the keels; lodicules wholly to partially connate; anthers 1, 2, or 3. Caryopses ovoid-oblong; hila ovoid to oblong.

Glyceria sect. Hydropoa includes approximately five species. Three species grow in the Flora region; one is introduced. They grow along streams and at the edges of lakes and ponds.

 

1. Glyceria grandis S. Watson
American Glyceria, American Mannagrass

Plants perennial. Culms 50–150 (200) cm tall, 8–12 mm thick, erect or decumbent and rooting at the base. Sheaths smooth or scabridulous, keeled; ligules 1–5 (7) mm, truncate to rounded, ligules of the lower leaves stiff at the base, ligules of the upper leaves flexible throughout; blades 25–43 cm long, 4.5–15 mm wide. Panicles 16–42 cm long, 12–20 cm wide, open; branches (7)10–18 cm, lax, widely divergent to drooping, with 35–80+ spikelets; pedicels 1–15 mm. Spikelets 3.2–10 mm long, 2–3 mm wide, somewhat laterally compressed, oval to elliptic in side view, with 4–10 florets. Glumes mostly hyaline, usually the midvein of 1 or both glumes extending to the apices, apices acute; lower glumes 1–2.3 mm; upper glumes 1.5–2.7 mm; rachilla internodes 0.5–0.8 mm; lemmas 1.8–3 mm, prominently (5)7-veined, veins often scabridulous, intercostal regions smooth, apices rounded to truncate, sometimes erose, almost flat at maturity; paleas from shorter than to slightly longer than the lemmas, lengths more than 3 times widths, keels not winged, ciliolate, tips not strongly incurved, truncate to notched between the keels; anthers 3, 0.5–1.2 mm. Caryopses 1–1.5 mm. 2n = 20.

Glyceria grandis grows on banks and in the water of streams, ditches, ponds, and wet meadows, from Alaska to Newfoundland and south in the mountains to California, Arizona, and New Mexico in the western United States, and to Virginia and Tennessee in the eastern United States. It is similar to G. maxima, differing primarily in its shorter, flatter lemmas and shorter anthers. It is also confused with G. elata and Torreyochloa pallida. It differs from the former in having acute glumes with long veins, more evenly dark florets, flatter lemma apices, and paleal keel tips that do not point towards each other. It differs from Torreyochloa pallida in its closed leaf sheaths and 1-veined glumes.

1. Spikelets 3.2–6.4 mm long, with 4–8 florets ... var. grandis
1. Spikelets 6–10 mm long, with 5–10 florets ... var. komarovii

 

Glyceria grandis S. Watson var. grandis
Giant Glyceria, Giant Mannagrass, Glycérie Géante

Spikelets 3.2–6.4 mm, with 4–8 florets.

Glyceria grandis var. grandis is the more widespread of the two varieties, growing throughout the range of the species.

 

Glyceria grandis var. komarovii Kelso

Spikelets 6–10 mm, with 5–10 florets.

Glyceria grandis var. komarovii is restricted to Alaska and the Yukon Territory.

 

2. Glyceria alnasteretum Kom.
Aleutian Glyceria

Plants perennial, rhizomatous. Culms 60–90 cm tall, 2.5–4 mm thick, erect. Sheaths smooth, not keeled; ligules 2–3 mm, rounded to truncate; blades 5–20 cm long, 3–7 mm wide, abaxial surfaces smooth, adaxial surfaces scabrous, apices acute. Panicles 15–22 cm long, 12–16 cm wide, open, pyramidal, erect to nodding; branches 8–10 cm, lower branches widely divergent to drooping. Spikelets 7–9 mm long, 3–4.5 mm wide, with 5–8 florets. Glumes unequal, lanceolate, acute; lower glumes 2–3.5 mm; upper glumes 2.5–3.5 mm, longer than wide; lemmas 3–5.5 mm, 7-veined, obtuse to acute; paleas shorter than or subequal to the lemmas, keels not winged, apices not strongly incurved, emarginate between the keels; anthers 3, 0.7–1.2 mm. Caryopses not seen. 2n = 20.

Glyceria alnasteretum is included in this treatment with some hesitation, based on van Schaack 724 (WTU 152646) and van Schaack 887 (MO 1710727), both collected at Signal Point, Attu Island, Alaska in 1945. The above description is based on Komarov (1963) and Koyama (1987), modified to reflect the wider panicles and longer glumes and lemmas of the van Schaack specimens. The difference in habitat is troubling. The van Schaack specimens were found “in a beachside meadow” and “near beach.” Koyama describes the habitat of G. alnasteretum as “wet meadows and marshes at high altitudes as well as subarctic zone” (p. 114). Nevertheless, the van Schaack specimens fit the description of G. alnasteretum better than any other taxon in this treatment. Clearly, further investigation is called for; it should include plants from both sides of the Bering Strait.

 

3. Glyceria maxima (Hartm.) Holmb.
Tall Glyceria, English Watergrass, Glycérie Aquatique

Plants perennial. Culms 60–250 cm tall, 6–12 mm thick, erect. Sheaths scabridulous, keeled; ligules 1.2–6 mm, rounded or with a central point, ligules of the lower leaves thick, stiff, and opaque, ligules of the upper leaves thinner and translucent; blades 30–60 cm long, 6–20 mm wide, both surfaces smooth or adaxial surfaces scabridulous. Panicles 15–45 cm long, to 30 cm wide, open; branches 8–20 cm, lax, strongly divergent or drooping at maturity, scabridulous, primary branches with 50+ spikelets; pedicels 0.8–10 mm. Spikelets 5–12 mm long, 2–3.5 mm wide, somewhat laterally compressed, oval in side view, with 4–10 florets. Glumes unequal, usually the midvein of 1 or both reaching to the apices; lower glumes 2–3 mm; upper glumes 3–4 mm, longer than wide; rachilla internodes 0.5–1 mm; lemmas 3–4 mm, 7-veined, veins scabridulous, apices broadly acute to rounded, slightly prow-shaped; paleas subequal to the lemmas, lengths more than 3 times widths, keels not winged, ciliate, tips not strongly incurved, curved to broadly notched between the keels; anthers 3, (1)1.2–2 mm. Caryopses 1.5–2 mm. 2n = 60.

Glyceria maxima is native to Eurasia. It grows in wet areas, including shallow water, at scattered locations in the Flora region. It is an excellent fodder grass, and may have been planted deliberately at one time (Dore and McNeill 1980). At some sites, the species appears to be spreading, largely vegetatively. It is easily confused with large specimens of G. grandis, but differs in its firmer, more prow-tipped lemmas as well as its larger lemmas and usually larger anthers.

 

Glyceria sect. Striatae G.L. Church

Plants perennial. Sheaths not or weakly compressed, midvein often conspicuous distally. Panicles 0.8–30 cm wide; branches usually ascending to strongly divergent or drooping, sometimes appressed. Spikelets oval in side view, lengths 1–4 times widths, laterally compressed. Lemmas with apices acute or obtuse to rounded, prow-shaped; paleas slightly shorter to slightly longer than the lemmas, keels well-developed, tips strongly incurved, apices narrowly notched between the keels; lodicules free; anthers 2. Caryopses usually obovoid, sometimes ovoid; hila punctate or linear.

Members of Glyceria sect. Striatae grow along streams, in swamps, and in shallow, fresh water. The section includes seven species, all of which are native to the Flora region.

 

4. Glyceria obtusa (Muhl.) Trin.
Atlantic Mannagrass

Plants perennial. Culms 60–100 cm tall, 2.5–5 mm thick, often decumbent at the base. Sheaths glabrous, smooth, not keeled, midvein prominent; ligules 0.5–0.8 mm, not translucent, truncate to slightly rounded; blades 15–40 cm long, 2–8 mm wide, abaxial surfaces smooth, adaxial surfaces scabridulous. Panicles 5–15 cm long, 2.5–6 cm wide, ovoid, erect, dense; branches 2.5–8 cm, strongly ascending, with 10–30 spikelets; pedicels 1–14 mm. Spikelets 4–7 mm long, 2.5–4 mm wide, somewhat laterally compressed, oval in side view, with 4–7 florets. Glumes keeled, 1–veined, veins not extending to the apical margins, apical margins hyaline, acute, entire or often splitting with age; lower glumes 1.6–2.5 mm, lanceolate to narrowly ovate or obovate; upper glumes 1.7–3.5 mm, ovate-elliptic to obovate, obtuse to rounded; rachilla internodes 0.2–0.4 mm; lemmas 3–3.9 mm, 5–9-veined, veins not raised, apices rounded, somewhat prow-shaped; paleas subequal to the lemmas, lengths 2–2.8 times widths, keels well-developed, not winged, tips pointing towards each other, narrowly notched between the keels; anthers 2, 0.6–0.8 mm. Caryopses 1.5–1.8 mm. 2n = 40.

Glyceria obtusa is a distinctive species that grows in wet woods, swamps, and shallow waters, primarily on the eastern seaboard of North America, from Nova Scotia and New Brunswick to South Carolina.

 

5. Glyceria melicaria (Michx.) F.T. Hubb.
Melic Mannagrass, Glycérie Melicaire

Plants perennial. Culms 50–100 cm tall, 3–5 mm thick, erect. Sheaths smooth, not or only weakly keeled; ligules 0.2–0.9 mm, translucent, rounded to truncate; blades 25–40 cm long, 2–7 mm wide, abaxial surfaces smooth, adaxial surfaces scab-ridulous. Panicles 15–25 cm long, 0.8–1.5 cm wide, linear, nodding; branches 5–9 cm, appressed, scarcely surpassing the node above, with 30–60+ spikelets; pedicels 0.5–2 mm. Spikelets 3.5–5 mm long, 1–2.5 mm wide, laterally compressed, oval in side view, with 3–4 florets. Glumes lanceolate, veins terminating below the apices, apices acute; lower glumes 1.3–2.4 mm; upper glumes 1.7–3 mm; rachilla internodes 0.4–0.6 mm; lemmas 1.9–2.8 mm, smooth or scabridulous, 5–7-veined, veins raised, apices acute, prow-shaped; paleas slightly shorter to slightly longer than the lemmas, lengths 2.5–4 times widths, keels well developed, not winged, tips incurved, narrowly notched between the keels; anthers 2, 0.3–0.5 mm. Caryopses 1–1.5 mm; hila subequal to the caryopses. 2n = 40.

Glyceria melicaria grows in swamps and wet soils. Its range extends from southeastern Ontario east to Nova Scotia, south to Illinois and the northeastern United States and, in the Appalachian Mountains, to northern Georgia. Glyceria ×gatineauensis Bowden is a sterile hybrid between G. melicaria and G. striata. For further comments, see description of Glyceria striata.

 

6. Glyceria nubigena W.A. Anderson
Great Smoky Mountain Mannagrass, Great Smoky Mountain Glyceria

Plants perennial. Culms 100–200 cm tall, 3–5 mm thick, smooth. Sheaths smooth or scabridulous, weakly keeled; ligules 1–1.5 mm, truncate; blades to 45 cm long, 6–10 mm wide, abaxial surfaces smooth or scabrous, adaxial surfaces scabrous. Panicles 20–30 cm long, 7.5–14 cm wide, open, pyramidal; branches 7.5–14 cm, spreading or reflexed, lax, with 16–80 spikelets; pedicels 2–7 mm. Spikelets 3.5–5.5 mm long, 2–3(3.5) mm wide, laterally compressed, oval in side view, with 3–5 florets. Glumes tapering from below midlength to the narrowly (< 45°) acute apices, veins not extending to the apices; lower glumes 0.8–1.5 mm; upper glumes 1.8–2.2 mm; rachilla internodes about 0.5 mm; lemmas 2.2–2.7 mm, 0.9–1.1 mm wide in dorsal view, veins distinctly raised, usually smooth over and between the veins, sometimes scabridulous over the veins, apices acute, prow-shaped; paleas slightly shorter than the lemmas, lengths 2–2.7 times widths, keels not winged, tips incurved, apices narrowly notched between the keels; anthers 2, about 1.5 mm, dehiscent at maturity. Caryopses about 1.5 mm. 2n = 40.

Glyceria nubigena is known only from moist areas of balds and high ridges in the Great Smoky Mountains of North Carolina and Tennessee.

 

7. Glyceria pulchella (Nash) K. Schum.
Beautiful Glyceria, Mackenzie Valley Mannagrass

Plants perennial. Culms 40–60 cm tall, 1.5–5 mm thick, erect. Sheaths scabridulous, not or weakly keeled; ligules 1.5–4 mm; blades 9–29 cm long, 2–7.5 mm wide, scabrous. Panicles 15–25 cm long, 6–15(20) cm wide, open, pyramidal, nodding; branches 8–12 cm, ascending to divergent, flexuous, often smooth, with 30–40+ spikelets; pedicels 0.3–6 mm. Spikelets 3.5–6 mm long, 1.4–2.5 mm wide, about 2.5 times longer than wide, laterally compressed, oval in side view, with 3–6 florets. Glumes unequal, lengths about 3 times widths, narrowing beyond midlength, veins terminating below the apices, apices acute, forming an angle of about 45°; lower glumes 1.5–2 mm; upper glumes 2–2.6 mm, erose; rachilla internodes 0.4–0.6 mm; lemmas 2.5–3.5 mm, oval in dorsal view, 7-veined, veins raised, scabridulous, apices broadly acute to obtuse, prow-shaped; paleas from shorter than to equaling the lemmas, lengths 3–3.5 times widths, keels not winged, tips incurved, apices narrowly notched between the keels; anthers 2, 0.5–0.9 mm. Caryopses about 1 mm. 2n = unknown.

Glyceria pulchella grows in marshes, muskegs, ponds, and ditches, from central Alaska and the Northwest Territories to southern British Columbia and central Manitoba. In overall aspect, G. pulchella resembles G. striata and G. elata. It differs in having somewhat stiffer and straighter panicle branches, in addition to larger spikelets and florets.

 

8. Glyceria striata (Lam.) Hitchc.
Ridged Glyceria, Glycérie Striée

Plants perennial. Culms 20–80 (100) cm tall, (1.5)2–3.5 mm thick, not or only slightly spongy, sometimes rooting at the lower nodes. Sheaths smooth to scab-ridulous, keeled, sometimes weak-ly so; ligules 1–4 mm, usually rounded, sometimes acute to mucronate, erose-lacerate; blades 12–30 cm long, 2–6 mm wide, abaxial surfaces smooth or scabridulous, adaxial surfaces scabridulous to scabrous. Panicles 6–25 cm long, 2.5–21 cm wide, pyramidal, open, nodding; branches 5–13 cm, straight to lax, lower branches usually strongly divergent to drooping at maturity, sometimes ascending, with 15–50 spikelets, these often confined to the distal 2/3; pedicels 0.5–7 mm. Spikelets 1.8–4 mm long, 1.2–2.9 mm wide, laterally compressed, oval in side view, with 3–7 florets. Glumes ovate, 1–1.5 times longer than wide, narrowing from midlength or above, veins terminating below the apical margins, apices often splitting with age; lower glumes 0.5–1.2 mm, rounded to obtuse; upper glumes 0.6–1.2 mm, acute or rounded; rachilla internodes 0.1–0.6 mm; lemmas 1.2–2 mm, ovate in dorsal view, veins raised, scabridulous over and between the veins, apices acute, prow-shaped; paleas slightly shorter than to equaling the lemmas, lengths 1.5–3 times widths, keeled, keels not winged, tips pointing towards each other, apices narrowly notched between the keels; anthers 2, (0.2)0.4–0.6 mm, purple or yellow. Caryopses 0.5–2 mm. 2n = 20 [reports of 28 are questionable].

Glyceria striata grows in bogs, along lakes and streams, and in other wet places. Its range extends from Alaska to Newfoundland and south into Mexico. Plants from the eastern portion of the range have sometimes been treated as G. striata var. striata, and those from the west as G. striata var. stricta (Scribn.) Fernald. Eastern plants tend to have somewhat narrower leaves and thinner culms than western plants, but the variation appears continuous. In the west, larger specimens are easy to confuse with G. elata. The two species are sometimes found growing together without hybridizing; this and molecular data (Whipple et al. [in prep.]) support their recognition as separate species. The differences between the two in growth habit and stature are evident in the field; they are not always evident on herbarium specimens. In its overall aspect, G. striata also resembles G. pulchella, but it has somewhat more lax panicle branches in addition to smaller spikelets and florets.

Glyceria ×gatineauensis Bowden is a sterile hybrid between G. striata and G. melicaria. It resembles G. melicaria but has longer (up to 12 cm), less appressed panicle branches and is a triploid with 2n = 30. It was described from a population near Eardley, Quebec. An additional specimen, tentatively identified as G. ×gatineauensis, was collected in 1929 from French Creek in Upshur County, West Virginia.

Glyceria ×ottawensis Bowden is a sterile hybrid between G. striata and G. canadensis. It is intermediate between the two parents, and is known only from the original populations near Ottawa. It has sometimes been included in G. ×laxa (Scribn.) Scribn. [= G. canadensis var. laxa]; that taxon often produces viable seed, indicating that it is not a hybrid.

 

9. Glyceria elata (Nash) M.E. Jones
Tall Mannagrass

Plants perennial. Culms 75–150 cm tall, 2.5–8 mm thick, spongy, decumbent and rooting at the lower nodes. Sheaths scabridulous or hirtellous, not or weakly keeled; ligules 2.5–4(6) mm, truncate to acute, erose, puberulent; blades 19–40+ mm long, 6–12(15) mm wide, abaxial surfaces smooth or scabridulous, adaxial surfaces usually scabrous, sometimes scabridulous. Panicles 15–30 cm long, 12–30 cm wide, pyramidal, open; branches 12–17 cm, divergent to drooping, lax, with 30–50+ spikelets; pedicels 0.3–5 mm. Spikelets 3–6 mm long, 1.5–2.8 mm wide, laterally compressed, oval in side view, with 3–4(6) florets. Glumes 1–1.5(2) times longer than wide, narrowing beyond midlength, veins terminating below the apical margins, apices obtuse to rounded; lower glumes 0.7–1.5 mm; upper glumes 1–1.5 mm; rachilla internodes 0.5–0.6 mm; lemmas 1.7–2.2 mm, oval in dorsal view, 5–7-veined, veins raised throughout, scabridulous, apices rounded, prow-shaped; paleas subequal to or often slightly longer than the lemmas, lengths 2.4–3 times widths, oval in dorsal view, keels not winged, tips pointing towards each other, apices narrowly notched between the keels; anthers 2, 0.5–0.8 mm. Caryopses 0.8–1.5 mm long, 0.5–0.7 mm wide; hila as long as the caryopses. 2n = 20.

Glyceria elata grows in wet meadows and shady moist woods, from British Columbia east to Alberta and south to California and New Mexico. It is not known from Mexico. The anomalous record from Georgia may represent an inadvertent introduction. It is very similar to, and sometimes confused with, G. striata, but the two sometimes grow together and show no evidence of hybridization. Their differences in growth habit and stature are evident in the field. Molecular data (Whipple et al. [in press]) confirm that G. elata and G. striata are distinct, closely related entities.

Glyceria elata is also sometimes confused with G. grandis. It differs in having rounded glumes with veins that terminate below the apices, more readily disarticulating florets, and greener lemmas with more prow-shaped apices, as well as in having paleal keel tips that point towards each other. In its overall aspect, it also resembles G. pulchella, but has somewhat more lax panicle branches than that species, in addition to smaller spikelets and florets.

 

10. Glyceria canadensis (Michx.) Trin.

Plants perennial. Culms 60–150 cm tall, 2.5–5 mm thick, erect or the bases decumbent. Sheaths retrorsely scabridulous to scabrous, keeled; ligules 2–6 mm; blades 8–36 cm long, 3–8 mm wide, abaxial surfaces smooth or scabrous, adaxial surfaces scabridulous to scabrous. Panicles 10–30 cm long, 10–20 cm wide, pyramidal, open, nodding; branches 7–20 cm, lax, divergent, often drooping, with 15–60+ spikelets; pedicels 2.5–9 mm. Spikelets 3–8 mm long, (2.5)3–5 mm wide, laterally compressed, oval in side view, with 2–10 florets. Glumes narrowing from midlength or above to the broadly (> 45°) acute or rounded apices, 1-veined, veins terminating below the apices; lower glumes 0.6–2.4 mm, ovate to rectangular; upper glumes 1.5–2.5 mm, lanceolate; rachilla internodes 0.2–0.5 mm; lemmas 1.8–4 mm, ovate in dorsal view, 5–7-veined, veins evident but not raised distally, smooth over and between the veins, apices acute, prow-shaped; paleas 0.1–0.8 mm shorter than lemmas, lengths 1.5–1.8 times widths, almost round in dorsal view, keels well developed, not winged, tips incurved, apices narrowly notched between the keels; anthers 2, 0.4–0.5 mm, dehiscent at maturity. Caryopses 1.5–2 mm.

Glyceria canadensis is an attractive native species that grows in swamps, bogs, lakeshore marshes, and wet woods throughout much of eastern North America, extending from eastern Saskatchewan to Newfoundland, Illinois, and northeastern Tennessee. It is now established in western North America, having been introduced as a weed in cranberry farms. It forms sterile hybrids with G. striata; the hybrids are called G. ×ottawensis Bowden. For further comments, see the description of Glyceria striata.

1. Lemmas 2.4–4 mm long; spikelets 5–8 mm long, with 4–10 florets; lower glumes 1.6–2.4 mm long; upper glumes acute ... var. canadensis
1. Lemmas 1.8–2.5 mm long; spikelets 3–5 mm long, with 2–5 florets; lower glumes 0.6–1.3 mm long; upper glumes usually rounded, sometimes acute ... var. laxa

 

Glyceria canadensis (Michx.) Trin. var. canadensis
Canadian Glyceria, Canadian Mannagrass, Rattlesnake Mannagrass, Glycérie du Canada

Spikelets 5–8 mm, with 4–10 florets. Lower glumes 1.6–2.4 mm; upper glumes 1.8–2.5 mm, acute; lemmas 2.4–4 mm. 2n = 60.

Glyceria canadensis var. canadensis grows throughout the range of the species. The spikelets bear some resemblance to those of Bromus briziformis, otherwise known as rattlesnake brome, hence the vernacular name “rattlesnake mannagrass”.

 

Glyceria canadensis var. laxa (Scribn.) Hitchc.
Limp Mannagrass

Spikelets 3–5 mm, with (2)3–5 florets. Lower glumes 0.6–1.3 mm; upper glumes 1.5–2.3 mm, usually rounded, sometimes acute; lemmas 1.8–2.5 mm. 2n = 60.

Glyceria canadensis var. laxa grows in swamps, bogs, and wet woods, primarily along the eastern seaboard of North America from Nova Scotia to northeastern Tennessee. It is sometimes treated as a hybrid, G. ×laxa (Scribn.) Scribn., but several specimens have dehiscent anthers and well-formed caryopses, indicating that they are not hybrids. The report of 2n = 30 is based on counts for G. ×ottawaensis.

 

Glyceria R. Br. sect. Glyceria

Plants perennial, rarely annual. Sheaths compressed, usually at least weakly keeled. Inflorescences 0.5–5 cm wide if the branches appressed, to 20 cm wide if divergent; branches usually appressed to ascending, divergent at anthesis; pedicels 0.5–5 mm. Spikelets cylindrical and terete, except at anthesis when slightly laterally compressed, rectangular in side view, appressed to the panicle branches, lengths 5–22 times widths. Lemmas rounded over the back, apices acute to rounded or truncate, entire to irregularly lobed; paleas keeled, keels usually winged distally, tips parallel or almost so, sometimes extending into teeth, truncate, rounded, or notched between the keels; lodicules connate; anthers 3. Caryopses ovoid-oblong; hila about as long as the caryopses, linear.

Glyceria sect. Glyceria includes about 15 species. Seven species grow in the Flora region, three of which are introduced. In addition, there is one named hybrid. They grow in and beside shallow, still or slowly moving fresh water, such as along the edges of lakes and ponds and in low areas in wet meadows.

 

11. Glyceria borealis (Nash) Batch.
Boreal Glyceria, Boreal Mannagrass, Glycérie Boreale

Plants perennial. Culms 60–100 cm tall, 1.5–5 mm thick, often decumbent and rooting at the lower nodes. Sheaths glabrous, keeled; ligules 4–12 mm; blades 9–25 cm long, 2–7 mm wide, often floating, abaxial surfaces smooth, adaxial surfaces of the midcauline leaves densely papillose, glabrous. Panicles 18–40(50) cm long, 0.5–2(5) cm wide, arching, usually narrow, open at anthesis, bases often enclosed in the upper leaf sheath at maturity; branches 5–10(15) cm, usually 1–3(5) per node, usually appressed to strongly ascending, occasionally spreading, longer branches with 3–6 spikelets; pedicels 1.2–5 mm. Spikelets 9–22 mm long, 0.8–2.5 mm wide, cylindrical and terete, except at anthesis when slightly laterally compressed, rectangular in side view, with 8–12 florets. Glumes elliptic, apices rounded to obtuse, sometimes erose; lower glumes 1.2–2.2 mm; upper glumes 2–3.8 mm, rounded; rachilla internodes 0.6–3.5 mm; lemmas 2.7–5.4 mm, veins raised, scabridulous or smooth, intercostal regions usually smooth, sometimes scabridulous, midvein terminating about (0.1)0.2 mm short of the apical margin, apices usually acute, sometimes obtuse, entire or almost so; paleas usually shorter than to equaling the lemmas, sometimes exceeding them by up to 0.5 mm, keels narrowly winged, apices bifid, teeth to 0.2 mm, parallel to weakly incurved; anthers 3, 0.4–1.5 mm. Caryopses 1.2–2 mm. 2n = 20.

Glyceria borealis is a widespread native species that grows in the northern portion of the Flora region, extending southward through the western mountains into northern Mexico. It grows along the edges and muddy shores of freshwater streams, lakes, and ponds. In the southern portion of its range, G. borealis is restricted to subalpine and alpine areas. The midcauline leaves of G. borealis almost always have densely papillose upper leaf surfaces. Voss (1972) stated that such surfaces are non-wettable and develop on the floating leaves.
Glyceria borealis differs from G. notata in having acute lemmas and, usually, densely papillose midcauline leaves.

 

12. Glyceria septentrionalis Hitchc.
Northern Glyceria, Northern Mannagrass, Glycérie Septentrionale

Plants perennial. Culms 73–182 cm tall, to 8 mm thick, often decumbent and rooting from the lower nodes. Sheaths smooth or scabridulous, keeled; ligules 5–16 mm; blades 18–32 cm long, 2–15 mm wide, abaxial surfaces scabrous, adaxial surfaces scabridulous, usually glabrous, midcauline leaves sometimes papillose. Panicles 15–60 cm long, 1–3.5 cm wide; branches 3–17 cm, usually erect to strongly ascending, sometimes spreading at anthesis, usually straight, sometimes lax, with 1–9 spikelets; pedicels 0.7–1.7 mm. Spikelets (6.5)10–23 mm long, 1–3 mm wide, cylindrical and terete, except at anthesis when slightly laterally compressed, rectangular in side view, with 8–16 florets. Glumes elliptic to obovate, apices rounded to acute; lower glumes (0.3)1.5–3.7 mm; upper glumes (1.9)2.3–5.2 mm; rachilla internodes 1.1–1.8 mm; lemmas 2.4–4.8 mm, veins scabrous or hispidulous, intercostal regions scabridulous, scabrous, or hispidulous, midveins extending to within 0.1 mm of the apical margins, apices truncate to obtuse or acute, apical margins crenate to entire; paleas from slightly shorter than to exceeding the lemmas, apices bifid, teeth to 0.2 mm; anthers 3, 0.5–1.8 mm. Caryopses 1.5–2 mm; hila about as long as the caryopses.

Glyceria septentrionalis is native and restricted to North America. It grows in shallow water or very wet soils, from southern Quebec to the east coast and south to eastern Texas and South Carolina. Voss (1972) stated that it is the floating leaves of G. septentrionalis that develop papillose, non-wettable adaxial surfaces. They seem to be developed less often than in G. borealis; whether this reflects a difference in habitat or growth habit is not known.

Glyceria septentrionalis resembles G. notata in its rather short, truncate to rounded lemmas, but it tends to have fewer spikelets on its branches. In addition, the veins of its leaf sheaths appear completely smooth, even under high magnification. That said, many specimens will be hard to identify if their provenance is not known.

1. Lemmas hispidulous over the veins, hairs about 0.1 mm long ... var. arkansana
1. Lemmas scabrous over the veins, prickles about 0.05 mm long ... var. septentrionalis

 

Glyceria septentrionalis var. arkansana (Fernald) Steyerm. & Kučera

Ligules 5–14 mm; blades 6–12 mm wide. Panicle branches 3–7 cm, with 3–5 spikelets. Rachilla internodes 0.5–1.5 mm. Lemmas hispidulous over the veins, hairs about 0.1 mm, hispidulous, scabrous, or scabridulous between the veins, apices rounded to acute, crenate. 2n = unknown.

Glyceria septentrionalis var. arkansana grows in roadside ditches and on the edges of swamps, lakes, and ponds in the flood plain of the Mississippi River, from southern Illinois and Indiana to the Gulf coast. There is also one record from central Tennessee (Chester et al. 1993). The size of its stomates suggests that var. arkansana, like var. septentrionalis, is a tetraploid.

 

Glyceria septentrionalis Hitchc. var. septentrionalis

Ligules 5–10 mm; blades 2–15 mm wide. Panicle branches 3–17 cm, with 1–9 spikelets. Rachilla internodes 1.1–1.8 mm. Lemmas scabrous over the veins, prickles about 0.05 mm, scabrous or scabridulous between the veins, apices almost truncate to obtuse or acute, apical margins crenate to entire. 2n = 40.

Glyceria septentrionalis var. septentrionalis grows throughout the range of the species, but is less common in the lower floodplain of the Mississippi River and Kentucky than var. arkansana. It is found in shallow water or wet soils. In reviewing specimens for this treatment, some were found to have acute lemmas that usually exceeded the paleas, and lemma midveins that were clearly longer than the other veins; others had truncate to obtuse lemmas that were usually shorter than or equaling the paleas, and lemma midveins that were barely longer than the lateral veins. Further study is needed to determine whether the two kinds merit separate recognition.

 

13. Glyceria acutiflora Torr.
Creeping Mannagrass

Plants perennial. Culms 30–100 cm tall, 3–6 mm thick, spongy, usually decumbent and rooting at the lower nodes. Sheaths smooth, weakly keeled; ligules 5–9 mm; blades 10–15 cm long, 3–8 mm wide, abaxial surfaces smooth, adaxial surfaces of the midcauline leaves often papillose. Inflorescences often racemes, sometimes panicles, 15–35 cm long, 1–2 cm wide, open at anthesis, bases often enclosed in the flag leaf sheaths at maturity; branches 5.5–8 cm (absent in racemose plants), solitary or in pairs, appressed, most branches with 1–3 spikelets, the lower branches sometimes with more than 3; pedicels 1.5–2.5 mm. Spikelets 20–45 mm long, 2.5–3 mm wide, cylindrical and terete except slightly laterally compressed at anthesis, rectangular in side view, with 5–12 florets. Glumes unequal, acute; lower glumes 1.3–4.5 mm; upper glumes 3–7 mm; rachilla internodes 2–3 mm; lemmas 6–8.5 mm, scabridulous, 7-veined, gradually tapering from near midlength to the narrowly acute (< 45°) or acuminate apices; paleas 0.7–3 mm longer than the lemmas, keels winged, tips parallel, intercostal region truncate, often splitting, apices appearing bifid, with 0.4–1 mm teeth; anthers 3, 1–2 mm. Caryopses about 3 mm. 2n = 40.

Glyceria acutiflora grows in wet soils and shallow water of the northeastern United States, extending from Michigan and Missouri to the Atlantic coast between southwestern Maine and Delaware. Its long paleas make G. acutiflora the most distinctive North American species of sect. Glyceria.

 

14. Glyceria leptostachya Buckley
Narrow Mannagrass

Plants perennial. Culms 50–100 (150) cm tall, 3–8 mm thick, spongy, erect to decumbent and rooting at the lower nodes. Sheaths finely scabridulous, not or weakly keeled; ligules 4.5–12 mm, lacerate; blades 12–30 cm long, 3.5–11 mm wide, both surfaces sometimes scabridulous, adaxial surfaces sometimes sparsely papillose. Panicles 20–40 cm long, 2.5–8 cm wide; branches 4.2–14.7 cm, appressed to ascending, with 3–8(10) spikelets; pedicels 2–5 mm, scabrous. Spikelets 9–20 mm long, 0.4–3 mm wide, cylindrical and terete, except at anthesis when slightly laterally compressed, rectangular in side view, with 6–15 florets. Glumes broadly rounded to acute; lower glumes 0.6–2.1 mm; upper glumes 1.4–3.4 mm; rachilla internodes 1–1.5 mm; lemmas 2.6–4.5 mm, somewhat indented below the apical margins at maturity, veins raised, scabridulous to scabrous over and between the veins, prickles about 0.05 mm, midveins extending to within 0.1 mm of the apical margins, apices truncate to obtuse, crenulate; paleas shorter than or equaling the lemmas, keels winged, tips parallel, intercostal region truncate or rounded, sometimes exceeding the keel tips; anthers 3, 0.3–0.9 mm. 2n = 40.

Glyceria leptostachya grows in swamps and along the margins of streams and lakes, on the western side of the coastal mountains from southern Alaska to San Francisco Bay. It is similar to the European Glyceria notata, differing primarily in its tendency to have fewer spikelets [3–8(10) vs. 5–15(19)] on its branches.

 

15. Glyceria ×occidentalis (Piper) J.C. Nelson
Western Mannagrass

Plants perennial. Culms 60–160 cm tall, 2.5–5 mm thick, erect or decumbent and rooting from the lower nodes. Sheaths smooth to scabridulous, keeled, sometimes weakly so; ligules 7–12 mm; blades 20–30 cm long, (2.5)4–12 mm wide, adaxial surfaces scab-ridulous, occasionally papillose. Panicles 20–50 cm long, 2–15 cm wide, usually narrow, open at anthesis; branches 4.5–18 cm, somewhat lax, usually ascending, strongly divergent at anthesis, with 2–8 spikelets, pedicels 1.5–8 mm. Spikelets 13–23 mm long, 1.5–3.5 mm wide, cylindrical and terete, except at anthesis when slightly laterally compressed, rectangular in side view, with 6–13 florets. Glumes acute to obtuse; lower glumes 1.1–2.8 mm; upper glumes 2.9–3.7 mm, about twice as long as the lower glumes; rachilla internodes 1–2.8 mm; lemmas 4.5–5.9 mm, scabridulous, midveins extending to within 0.1 mm of the apical margins, apices acute, usually slightly lobed or irregularly crenate; paleas usually shorter than or equaling the lemmas, sometimes slightly longer, keels winged, apices shallowly notched to slightly bifid, teeth to 0.2 mm, parallel; anthers 2, 0.6–1.6 mm. 2n = 40.

Glyceria ×occidentalis has hitherto been considered an uncommon native species that grows along lakes, ponds, and streams, and in marshy areas of western North America. It differs from other species in the region primarily in its longer lemmas and anthers. Studies of chloroplast DNA in western North American species of Glyceria demonstrated that, contrary to C.L. Hitchcock’s (1969) conclusion, G. fluitans is present in western North America, and that all specimens being identified as G. ×occidentalis had cpDNA resembling that of G. leptostachya or G. fluitans; there was no distinctive G. ×occidentalis cpDNA (Whipple et al. [in press]). This strongly suggests that G. ×occidentalis is a series of reciprocal hybids, and probably backcrosses, between G. fluitans and G. leptostachya. As the key indicates, G. ×occidentalis is intermediate between its two putative parents. The cpDNA study also confirmed that G. declinata is distinct from G. ×occidentalis (see discussion under that species).

 

16. Glyceria fluitans (L.) R. Br.
Water Mannagrass, Glycérie Flottante

Plants perennial. Culms 20–150 cm tall, 2–4 mm thick, erect or spreading, sometimes decumbent and rooting from the lower nodes, distal portion sometimes floating in shallow water. Sheaths glabrous, keeled; ligules 5–15 mm; blades 5–25 cm long, 3–10 mm wide, both surfaces smooth. Panicles 10–50 cm long, 2–3 cm wide; branches 3–5 cm, paired or solitary, usually appressed to ascending, divergent at anthesis, with 1–4 spikelets; pedicels 0.8–20 mm. Spikelets (15)18–39 mm long, 1.7–3.3 mm wide, cylindrical and terete, except slightly laterally compressed at anthesis, rectangular in side view, with 8–16 florets. Lower glumes 1.3–3.9 mm; upper glumes 2.7–5 mm; rachilla internodes 1.9–2.5 mm; lemmas 5.2–8 mm, midveins extending to within 0.1 mm of the apical margins, scabrous over and between the veins, prickles about 0.05 mm, apices acute, usually entire; paleas from shorter than to 0.6(1.5) mm longer than the lemmas, keels winged, apices bifid, teeth 0.1–0.4 mm, parallel to convergent, sometimes crossing when dry; anthers 1.5–3 mm, usually purple. Caryopses 2–3 mm. 2n = 40.

Glyceria fluitans is a Eurasian species. In the Americas, it has been collected from British Columbia to California on the west coast, in South Dakota, and from Newfoundland to Pennsylvania on the eastern seaboard. In Europe, it grows in rich, organic, wet soils, often near G. notata, with which it hybridizes. It is less tolerant of trampling than G. notata. Many earlier reports from eastern Canada are based on G. borealis or G. septentrionalis (Dore and McNeill 1980; Scoggan 1978). In western North America, it has been confused with G. ×occidentalis. It tends to differ from all three in its longer lemmas and anthers. Nevertheless, identification of some specimens will prove troublesome. For further discussion, see under the species mentioned.

 

17. Glyceria declinata Bréb.
Low Glyceria

Plants usually perennial, rarely annual. Culms (10)20–92 cm tall, 1.5–2.5 mm thick, ascending to erect from a decumbent, branching base. Sheaths glabrous, keeled; ligules 4–9 mm; blades (2)3–12 cm long, 4–8 mm wide, adaxial surfaces not papillose, apices abruptly acute. Panicles 6–30 cm long, 1–2.5 cm wide; branches 1.5–9.5 cm, ascending, with 1–5 spikelets; pedicels 1–2.5 mm. Spikelets 11–24 mm long, 1.3–3 mm wide, cylindrical and terete, except slightly laterally compressed at anthesis, rectangular in side view, with 8–15 florets. Glumes oval; lower glumes 1.4–3.5 mm; upper glumes 2.5–4.9 mm; rachilla internodes 1.2–1.8 mm; lemmas (3.5)4–6 mm, 7-veined, veins and intercostal regions scabridulous, prickles about 0.05 mm, midveins extending to within 0.1 mm of the apical margins, apices acute, with a well-developed lobe on one or both sides opposite the lateral veins, entire to crenulate between the lateral lobes; paleas exceeding the lemmas by 0.2–1(1.5) mm, keels winged, apices bifid, teeth 0.3–0.5 mm; anthers 0.5–1.4 mm, usually purple. Caryopses 1.8–2.5 mm. 2n = 20.

Glyceria declinata is a European species that is established on the western seaboard of North America from southern British Columbia to southern California, and in northeastern Nevada, Arizona, the lower portion of the Mississippi valley, and on Long Island, New York. In Europe, it grows in low-calcium, acidic soils and tolerates drier conditions than other European species of Glyceria (Conert 1992). In Denmark, it tends to grow in areas that are highly trampled (Niels Jacobsen and Signe Frederiksen, pers. comm.). It is invading vernal pools in California.

In western North America, G. declinata has been confused with G. ×occidentalis. The most reliable distinguishing characteristics are the lateral lemma lobes of G. declinata and its rather short, straight panicle branches. The two species also differ in their ploidy level, G. declinata being diploid and G. ×occidentalis tetraploid (Church 1949). This is reflected in the length of their guard cells, those of G. declinata being 0.2–0.3 µm and those of G. ×occidentalis being 0.4–0.5 µm.

S.F. Hrusa found plants (Hrusa 13681, 15858, 16267; specimens in CDA) that have an annual growth habit. Apart from this, they fit within the circumscription of G. declinata, except that two of the three specimens have narrower (2–3 mm) leaves than normal; they were also collected relatively early in the season. For now, it seems best to include the plants in G. declinata pending a better understanding of their relationship to perennial members of the species.

 

18. Glyceria notata Chevall.
Marked Glyceria

Plants perennial. Culms 25–80 cm, rooting at the nodes. Sheaths usually scabridulous or hirtellous; ligules 2–8 mm; blades 5–30 cm long, 3–11(14) mm wide, abaxial surfaces scabrous, adaxial surfaces sometimes scabridulous to scabrous, sometimes sparsely hairy, sometimes papillose. Panicles 10–45 cm; branches 2–5 per node, eventually widely spreading; branches to 12 cm, with 5–15(19) spikelets; pedicels 1–6 mm. Spikelets 10–25 mm long, 1.5–3 mm wide, cylindrical and terete except slightly laterally compressed at anthesis, rectangular in side view, with 7–16 florets. Glumes obtuse to rounded; lower glumes 1–2.5 mm; upper glumes 2.5–4.5 mm; lemmas 3.5–5 mm, the submarginal veins often longer than those adjacent to the midvein, veins scabridulous, smooth or scabridulous between the veins, apices truncate to rounded, crenulate; paleas from slightly shorter to slightly longer than the lemmas, keels winged distally, apices bifid, teeth about 0.2 mm; anthers 0.8–1.5 mm. Caryopses 1.5–2.5 mm. 2n = 40.

Glyceria notata is a Eurasian species that has been reported from scattered locations in the Flora region; the reports have not been verified. In Europe, G. notata grows in rich, organic, wet soils, often near G. fluitans, with which it hybridizes. It is more tolerant of trampling than G. fluitans.

There is no single morphological characteristic that separates Glyceria notata from G. septentrionalis and G. leptostachya. It more frequently has lemmas with short veins adjacent to the midvein than the other two species, is more frequently smooth between the veins, more frequently has scabridulous leaf sheaths, and tends to have more spikelets on its branches. The limited cpDNA data indicate that the three are distinct taxa (Whipple et al. [in press]). An intensive examination of the three species is needed.