17.30   SPOROBOLUS R. Br.

REVISED TREATMENT. Please send comments to Mary Barkworth.

Paul M. Peterson
Stephan L. Hatch
Alan S. Weakley

Plants annual or perennial; usually cespitose, sometimes rhizomatous, rarely stoloniferous. Culms 10-250 cm, usually erect, rarely prostrate, glabrous. Sheaths open, usually glabrous, often ciliate at the apices; ligules of hairs; blades flat, folded, involute, sometimes terete. Inflorescences terminal, open or contracted panicles, sometimes partially included in the uppermost sheath. Spikelets rounded to laterally compressed, with 1(-3) floret(s) per spikelet; disarticulation above the glumes. Glumes 0-1-veined; calluses poorly developed, usually glabrous; lemmas membranous or chartaceous, 1(3)-veined, unawned; paleas glabrous, 2-veined, often splitting between the veins at maturity; anthers (2)3. Fruits utricles or achenes, ellipsoid, obovoid, fusiform, or quadrangular, pericarp free from the seed, becoming mucilaginous when moist in most species, remaining dry and partially adherent to the seed in S. heterolepis and S. clandestinus. Cleistogamous spikelets occasionally present in the lower leaf sheaths. x = 9. Name from the Greek sporos, seed, and bolos, a throw, referring to the free seeds, which are sometimes forcibly ejected when the mucilaginous pericarp dries.

Sporobolus is a cosmopolitan genus of more than 160 species that grow in tropical, subtropical, and warm-temperate regions throughout the world. Seventy-four species are native to the Western Hemisphere; 27 are native to the Flora region, three are established introductions, one was introduced but has not persisted, and the status of one is uncertain. Two genera of the Western Hemisphere, Calamovilfa and Crypsis, resemble Sporobolus in having hairy ligules, spikelets with 1 floret, 1-veined lemmas, and fruits with a free pericarp (Peterson et al. 1997).

Note added December 13, 2005: Previously, Peterson was not sure that Sporobolus pyramidalis P. Beauv. occurred in the Flora region. However, he has now identified a specimen collected in the region as S. pyramidalis, a taxon that he considers distinct from S. jacquemontii Kunth and S. indicus (L.) R. Br.


SELECTED REFERENCES Baaijens, G.J. and J.F. Veldkamp. 1991. Sporobolus (Gramineae) in Malesia. Blumea 35:393-458; Laegaard, S. and P.M. Peterson. 2001. Flora of Ecuador 68 (ed. G. Harling & L. Andersson). 214(2). Gramineae (part 2): Subfam. Chloridoideae. Botanical Institute, University of Göteborg, Göteborg, Sweden and Section for Botany, Riksmuseum, Stockholm, Sweden. 131 pp.; McGregor, R.L.1990. Seed dormancy and germination in the annual cleistogamous species of Sporobolus (Poaceae). Trans. Kansas Acad. Sci. 93:8-11; Peterson, P.M., R.D. Webster and J. Valdés-Reyna. 1997. Genera of New World Eragrostideae (Poaceae: Chloridoideae). Smithsonian Contr. Bot. 87:1-50; Riggins, R. 1977. A biosystematic study of the Sporobolus asper complex (Gramineae). Iowa State J. Res. 51:287-321; Simon, B.K. and S.W.L. Jacobs. 1999. Revision of the genus Sporobolus (Poaceae, Chloridoideae) in Australia. Austral. J. Bot. 12:375-448; Turner, B.L. 2004. Sporobolus coahuilensis (Poaceae): A new record for the U.S.A. from Trans-Pecos, Texas. Sida 21:455-457; Weakley, A.S. and P.M. Peterson. 1998. Taxonomy of the Sporobolus floridanus complex (Poaceae: Sporobolinae). Sida 18:247-270.

1
Plants annuals or short-lived perennials flowering in the first year (2)
Plants perennial (7)
2
Lower panicle nodes with 7-20 branches (3)
Lower panicle nodes with 1-3 branches (4)
3
Pedicels 0.1-0.5(1) mm long, appressed ..... 2. S. pyramidatus
Pedicels (2)3-6(8) mm long, widely spreading ..... 4. S. coahuilensis
4
Spikelets 0.7-1.1 mm long; anthers 0.2-0.3 mm long ..... 1. S. tenuissimus
Spikelets 1.6-6 mm long; anthers 0.3-3.2 mm long (5)
5
Mature panicles 10-35 cm long, 4.5-30 cm wide, open; secondary branches spreading; pedicels usually 6-25 mm long, spreading ..... 20. S. texanus
Mature panicles 1-5 cm long, 0.2-0.5 cm wide, contracted; secondary branches appressed; pedicels usually 0.1-4 mm long, appressed (6)
6
Lemmas strigose; spikelets 2.3-6 mm long; mature fruits (1.1)1.8-2.7 mm long ..... 3. S. vaginiflorus
Lemmas glabrous; spikelets 1.6-3 mm long; mature fruits 1.2-1.8 mm long ..... 5. S. neglectus
7
Plants with rhizomes (8)
Plants without rhizomes (12)
8
Spikelets 1.4-3.2 mm long (9)
Spikelets 4-10 mm long (10)
9
Panicles 0.4-1.6 cm wide, spikelike, blades usually conspicuously distichous ..... 6. S. virginicus
Panicles 2.4-8 cm wide, somewhat contracted to lax and open, blades not obviously distichous ..... 13. S. fimbriatus
10
Panicles (0.6)1-8 cm wide, open to somewhat contracted, narrowly pyramidal, well-exserted from the uppermost sheath; branches without spikelets on the lower 1/3 ..... 26. S. interruptus
Panicles 0.04-1.6 cm wide, narrow or spikelike, partially to wholly included in the uppermost sheath; branches spikelet-bearing to the base (11)
11
Fruits 1-2 mm long; pericarp gelatinous, slipping from the seed when wet; panicles 5-30 cm long, 0.4-1.6 cm wide; lemmas glabrous, smooth ..... 7. S. compositus
Fruits (1.5)2.4-3.5 mm long; pericarp loose but neither gelatinous nor slipping from the seed when wet; panicles 5-11 cm long, 0.04-0.3 cm wide; lemmas minutely pubescent or scabridulous ..... 8. S. clandestinus
12
Upper glumes usually less than 2/3 as long as the florets (13)
Upper glumes at least 2/3 as long as the florets, often longer (16)
13
Lower panicle branches much shorter than the adjacent internodes, appressed to strongly ascending ..... 11. S. creber
Lower panicle branches usually as long as or longer than the adjacent internodes, appressed or ascending (14)
14
Spikelets 2-2.7 mm long; upper glumes usually 1/2-2/3 as long as the florets, acute to obtuse, entire ..... 9. S. indicus
Spikelets 1.3-1.8(2) mm long; upper glumes usually less than 1/2 as long as the florets, rarely longer; truncate, erose to denticulate (15)
15
Anthers 0.9-1.1 mm long, usually 3, rarely 2; branches spikelet-bearing to the base ..... 10. S. jacquemontii
Anthers 0.5-0.8 mm long, usually 2, rarely 3; branches without spikelets on the lower 1/4 ..... 12. S. diandrus
16
Spikelets 1-2.5(2.8) mm long (17)
Spikelets 2.5-10 mm long (31)
17
Lower sheaths keeled and flattened below ..... 14. S. buckleyi
Lower sheaths rounded below (18)
18
Panicles 12-35 cm wide, open (19)
Panicles 0.2-12(14) cm wide, contracted to open (22)
19
Sheath apices with a conspicuous tuft of white hairs; flag blades nearly perpendicular to the culms ..... 18. S. cryptandrus
Sheath apices glabrous or with a few scattered hairs; flag blades ascending (20)
20
Secondary panicle branches spikelet-bearing to the base; pedicels mostly appressed, mostly 0.2-0.5 mm long; panicles 20-60 cm long ..... 16. S. wrightii
Secondary panicle branches without spikelets on the lower 1/4-1/2; pedicels mostly spreading, mostly 0.5-25 mm long; panicles 10-45 cm long (21)
21
Pedicels 0.5-2 mm long; anthers 1.1-1.8 mm long ..... 17. S. airoides
Pedicels 6-25 mm long; anthers 0.3-1 mm long ..... 20. S. texanus
22
Mature panicles 0.2-5 cm wide, contracted, often spikelike, the panicle branches appressed or diverging no more than 30° from the rachises (23)
Mature panicles 4.5-30 cm wide, open, pyramidal to subovate or oblong, the panicle branches diverging more than 10° from the rachises, sometimes reflexed (27)
23
Primary panicle branches without spikelets on the lower 1/8-1/2 of their length (24)
Primary panicle branches spikelet-bearing to the base (26)
24
Leaf blades 1-1.5 mm wide; ligules 0.2-0.4 mm long ..... 21. S. nealleyi
Leaf blades 2-6 mm wide; ligules 0.3-1 mm long (25)
25
Lower panicle nodes with 7-12(15) branches; anthers 0.2-0.4 mm long ..... 2. S. pyramidatus
Lower panicle nodes with 1-3 branches; anthers 0.5-1 mm long ..... 18. S. cryptandrus
26
Lower glumes usually 1-veined; mature panicles 0.2-0.8(1) cm wide; lemmas 2-3.2 mm long, linear-lanceolate; upper glumes 2-3.2 mm long; anthers 3, 0.3-0.5 mm long; plants primarily from west of the Mississippi River ..... 19. S. contractus
Lower glumes usually without veins; mature panicles 1-5 cm wide; lemmas 1.1-2 mm long, ovate; upper glumes 1.1-2 mm long; anthers 2 or 3, 0.5-1 mm long; plants primarily from east of the Mississippi River ..... 15. S. domingensis
27
Lower panicle nodes with 7-12(15) branches; anthers 0.2-0.4 mm long ..... 2. S. pyramidatus
Lower panicle nodes with 1-2(3) branches; anthers 0.4-1 mm long (28)
28
Pedicels 6-25 mm long, spreading; panicles 4.5-30 cm wide, about as long as wide, diffuse ..... 20. S. texanus
Pedicels 0.1-3 mm long, appressed or spreading; panicles 0.3-14 cm wide, longer than wide, open and/or drooping (29)
29
Culms 10-50(60) cm tall, 0.7-1.2 mm thick near the base; plants with hard, knotty bases; blades (0.6)1.5-6(7) cm long, 1-1.5 mm wide, involute, spreading at right angles to the culms ..... 21. S. nealleyi
Culms 30-120 cm tall, 1-3.5 mm thick near the base; plant bases not hard and knotty; blades (2)5-26 cm long, 2-6 mm wide, flat to involute, ascending or at right angles to the culms (30)
30
Pedicels appressed to the secondary branches; primary branches appressed, spreading, or reflexed; pulvini glabrous; rachises straight, erect; mature panicles narrowly pyramidal, lower branches longer than the middle branches ..... 18. S. cryptandrus
Pedicels spreading from the secondary branches; primary branches reflexed; pulvini pubescent; rachises drooping or nodding; mature panicles subovate to oblong, lower branches no longer than those in the middle ..... 22. S. flexuosus
31
Lower panicle nodes with 3 or more branches (32)
Lower panicle nodes with 1-2(3) branches (33)
32
Mature panicles 2-6 cm wide, pyramidal; panicle branches diverging 20-100° from the rachises; blades 0.8-2 mm wide; fruits 1.4-1.8 mm long ..... 24. S. junceus
Mature panicles 0.4-1.6 cm wide, narrow, contracted; panicle branches appressed or diverging to 20° from the rachises; blades 2-5 mm wide; fruits 1.8-2.3 mm long ..... 25. S. purpurascens
33
Mature panicles 0.04-4 cm wide, spikelike; panicle branches appressed (34)
Mature panicles (0.6)1-30 cm wide, usually open, narrowly pyramidal to pyramidal or ovate; panicle branches appressed or spreading (37)
34
Spikelets 4-6(10) mm long, stramineous to purplish-tinged; panicles terminal and axillary; sheaths without a conspicuous apical tuft of hairs (35)
Spikelets 1.7-3.5(4) mm long, whitish to plumbeous; panicles all terminal; sheaths with a conspicuous apical tuft of hairs (36)
35
Lemmas minutely pubescent or scabridulous, chartaceous and opaque; pericarps loose but neither gelatinous nor slipping off the seeds when wet; fruits (1.5)2.4-3.5 mm long ..... 8. S. clandestinus
Lemmas usually glabrous and smooth, membranous to chartaceous and hyaline; pericarps gelatinous, slipping off the seeds when wet; fruits 1-2 mm long ..... 7. S. compositus
36
Culms 40-100(120) cm tall, 2-4(5) mm thick near the base; mature panicles 0.2-0.8(1) cm wide; anthers 0.3-0.5 mm long ..... 19. S. contractus
Culms 100-200 cm tall, (3)4-10 mm thick near the base; mature panicles 1-4 cm wide; anthers 0.6-1 mm long ..... 23. S. giganteus
37
Spikelets 2.3-3 mm long; panicles 4.5-30 cm wide, diffuse, about as long as wide; branches capillary; anthers 0.3-1 mm long ..... 20. S. texanus
Spikelets 3-7.2 mm long; panicles 0.6-15 cm wide, longer than wide, not diffuse; branches not capillary; anthers 1.5-5 mm long (38)
38
Mature spikelets plumbeous; sheath bases dull, fibrous (39)
Mature spikelets purplish-brown to purplish; sheath bases shiny, indurate (40)
39
Anthers 3-4.2 mm long; ligules 0.2-0.7 mm long; plants from Arizona ..... 26. S. interruptus
Anthers 1.7-3 mm long; ligules 0.1-0.3 mm long; plants not known from Arizona ..... 27. S. heterolepis
40
Blades 0.5-1.2 mm wide, subterete to terete in cross section, at least at the base, sometimes channeled for portions of their length, sometimes becoming tightly involute distally, senescing or turning tan in late fall, the margins smooth; pedicels with scattered ascending hairs ..... 28. S. teretifolius
Blades 0.8-10 mm wide, flat or V-shaped in cross section, flat, folded, or involute when dry, remaining green well into winter or yellowing at maturity, the margins usually scabridulous, occasionally smooth; pedicels glabrous, sometimes scabridulous or scabrous (41)
41
Lower glumes from 0.9 times as long as to longer than the upper glumes; culms 30-80(90) cm tall; panicles 10-25 cm long; pedicels 0.5-4(8) mm long, usually shorter than the spikelets, appressed ..... 29. S. curtissii
Lower glumes from 0.6-0.9 (0.94) times as long as the upper glumes; culms (30)45-250 cm tall; panicles 15-50 cm long; pedicels 2-22 mm long, spreading or appressed (42)
42
Pedicels appressed; lemmas 4.4-6.5 mm long; anthers 3.5-5 mm long; spikelets purplish ..... 30. S. silveanus
Pedicels spreading; lemmas 3-4.3 mm long; anthers 2-3.4 mm long; spikelets purplish-brown (43)
43
Blades (2)3-10 mm wide, pale bluish-green, yellowing at maturity; panicles (18)30-50 cm long, 4-15 cm wide; lower glumes (0.6)0.75-0.94 times as long as the upper glumes ..... 31. S. floridanus
Blades 1.2-2(3) mm wide, dark green, remaining green well into winter; panicles 15-30 cm long, 2-6 cm wide; lower glumes 0.6-0.83 times as long as the upper glumes ..... 32. S. pinetorum


1.   Sporobolus tenuissimus (Mart. ex Schrank) Kuntze
Tropical Dropseed

Plants annual; tufted. Culms 30-100 cm. Sheaths glabrous, including the apices; ligules 0.2-0.3 mm; blades 5-23 cm long, 2-4 mm wide, flat or folded, glabrous on both surfaces, margins glabrous. Panicles (8)15-30 cm long, 3.5-8 cm wide, open, diffuse, cylindrical; lower nodes with 1-2(3) branches; primary branches 0.6-5 cm, capillary, spreading 30-70° from the rachises, without spikelets on the lower 1/2; secondary branches spreading; pedicels 0.5-5 mm. Spikelets 0.7-1.1 mm, plumbeous to purplish. Glumes unequal, obovate to ovate, membranous; lower glumes 0.1-0.4 mm, occasionally absent; upper glumes 0.2-0.5 mm; lemmas 0.7-1.1 mm, elliptic, membranous, glabrous, acute to obtuse; paleas 0.7-1.1 mm, elliptic, membranous; anthers 0.2-0.3 mm, yellowish. Fruits 0.4-0.7 mm, pyriform or quadroid, somewhat laterally flattened, light brownish to whitish. 2n = 12.

Sporobolus tenuissimus is native to the Western Hemisphere, and introduced to Africa and Asia. Its native distribution in the Americas is tropical, extending from southern Mexico to Brazil and Paraguay. It has been found at a few locations in the southeastern United States, at 0-100 m. It grows in disturbed areas, often occurring as a weed in gardens and cultivated fields.


2.   Sporobolus pyramidatus (Lam.) Hitchc.
Whorled Dropseed

Plants annual or short-lived perennials flowering in the first year; cespitose, not rhizomatous. Culms 7-35(60) cm, erect or decumbent. Sheaths rounded below, margins and apices hairy, hairs to 3 mm; ligules 0.3-1 mm; blades 2-12(20) cm long, 2-6 mm wide, flat, abaxial surface glabrous, adaxial surface scabridulous, sometimes sparsely hispid, margins ciliate-pectinate. Panicles 4-15(18) cm long, 0.3-6 cm wide, open (contracted when immature), pyramidal; lower nodes with 7-12(15) branches; primary branches 0.5-4.5 cm, spreading 30-90° from the rachis, with elongated glands, without spikelets on the lower 1/3-1/2; secondary branches appressed; pedicels 0.1-0.5 mm, appressed. Spikelets 1.2-1.8 mm, plumbeous or brownish, often secund along the branch. Glumes unequal, ovate to obovate, membranous; lower glumes 0.3-0.7 mm, without midveins; upper glumes 1.2-1.8 mm, at least 2/3 as long as the florets, often longer; lemmas 1.2-1.7 mm, ovate to elliptic, membranous, glabrous, acute; paleas 1.1-1.6 mm, ovate to elliptic, membranous, glabrous; anthers 0.2-0.4 mm, yellowish or purplish. Fruits 0.6-1 mm, obovoid, faintly striate, light brownish. 2n = 24, 36, 54.

Sporobolus pyramidatus is native to the Americas, extending from the southern United States to Argentina. It grows in disturbed soils, roadsides, railways, coastal sands, and alluvial slopes in many plant communities, at elevations from 0-1500 m. Morphologically, it is very similar to the Eastern Hemisphere S. coromandelianus (Retz.) Kunth, suggesting that they are closely related.


3.   Sporobolus vaginiflorus (Torr. ex A. Gray) Alph. Wood
Poverty Grass, Sporobole Engainé

Plants annual; tufted, delicate. Culms 15-60(70) cm, erect to decumbent, wiry. Sheaths often inflated, sometimes with sparse hairs basally, hairs papillose-based, glabrous or the apices with small tufts of hairs, hairs to 3 mm; ligules 0.1-0.3 mm; blades 2-12(25) cm long, 0.6-2 mm wide, flat to loosely involute, glabrous abaxially, scabridulous adaxially, bases of both surfaces sometimes with a few papillose-based hairs, margins smooth or scabridulous. Panicles terminal and axillary, 1-5 cm long, 0.2-0.5 cm wide, contracted, cylindrical, enclosed in the uppermost sheath; lower nodes with 1-2(3) branches; primary branches 0.4-1.8 cm, appressed, spikelet-bearing to the base; secondary branches appressed; pedicels 0.2-4 mm, appressed, scabridulous. Spikelets 2.3-6 mm, yellowish to purplish- or grayish-mottled. Glumes subequal, linear-lanceolate to lanceolate-triangular or ovate, membranous to chartaceous, glabrous; lower glumes (2.2)2.8-4.7 mm; upper glumes (2.4)3-5 mm; lemmas (2.1)3-5.4 mm, lanceolate to lanceolate-triangular, 1-3-veined, chartaceous, often mottled with purplish or grayish areas, strigose, hairs less than 0.5 mm, apices acuminate or acute; paleas (2.1)3-6 mm, as long as or longer than the lemmas, sometimes tapering into a beak, lanceolate to lanceolate-triangular, chartaceous, strigose; anthers 3, 1.2-3.2 mm, yellowish or purplish. Fruits (1.1)1.8-2.7 mm, obovoid, laterally flattened, light brownish, translucent. 2n = 54.

Sporobolus vaginiflorus is a North American species, native to the eastern portion of the Flora region and probably introduced in the west. It grows in disturbed sites within many plant communities, commonly in sandy to sandy-clay soils, these often derived from calcareous parent materials. Its elevational range is 1-1250 m.

1
Sheath bases sparsely hairy; glumes usually longer than the florets; lemmas always faintly 3-veined ..... var. ozarkanus
Sheath bases usually glabrous; glumes usually shorter than the florets; lemmas usually 1-veined ..... var. vaginiflorus


Sporobolus vaginiflorus var. ozarkanus (Fernald) Shinners
Ozark Dropseed

Sheath bases sparsely hairy, hairs papillose-based. Spikelets 2.3-4.6 mm. Glumes usually longer than the florets; lemmas 2.1-3.9 mm, faintly 3-veined; paleas 2.1-4 mm. Fruits 1.1-2 mm.

Sporobolus vaginiflorus var. ozarkanus grows primarily in the central and southeastern United States.


Sporobolus vaginiflorus (Torr. ex A. Gray) Alph. Wood var. vaginiflorus

Sheath bases usually glabrous. Spikelets mostly 3-6 mm. Glumes usually shorter than the florets; lemmas mostly 3-5.4 mm, usually 1-veined, sometimes faintly 3-veined; paleas mostly 3-5.4 mm. Fruits 1.8-2.7 mm.

Sporobolus vaginiflorus var. vaginiflorus is the most wide-ranging of the two varieties, extending north into Canada.


4.   Sporobolus coahuilensis Valdés-Reyna

Plants annual. Culms 1560 cm, ascending, glabrous. Sheaths shorter than the internodes, glabrous; ligules 0.51 mm, ciliate; blades 412 cm long, 1.56 mm wide, flat, spreading, evenly distributed, adaxial surface sparsely ciliate-pustulate. Panicles 622 cm long, (1)513 cm wide, open, sometimes contracted; branches terminating in a spikelet, lowest branches whorled, in verticles of 720; pedicels (2)36(8) mm, widely spreading, capillary. Spikelets 1.11.5 mm. Glumes thin, acute; lower glumes about 0.5 mm; upper glumes 1.11.5 mm; lemmas 1.11.4 mm, acute; paleas 11.3 mm, hyaline. Fruits 0.60.9 mm, oblong, light brown; embryos 0.20.4 mm. 2n = unknown.

Sporobolus coahuilensis is primarily known from central Coahuila in Mexico. It has recently been found in Brewster and Hudspeth counties, Texas (Turner 2004).

Sporobolus coahuilensis appears closely related to the widespread species S. pyramidatus, and can be separated from the latter by its long capillary pedicels and usually wider panicles.


5.   Sporobolus neglectus Nash
Puffsheath Dropseed, Sporobole Négligé

Plants annual; tufted, delicate, slender. Culms 10-45 cm, wiry, erect to decumbent. Sheaths inflated, mostly glabrous but the apices with small tufts of hairs, hairs to 3 mm; ligules 0.1-0.3 mm; blades 1-12 cm long, 0.6-2 mm wide, flat to loosely involute, abaxial surface glabrous, adaxial surface scabridulous, bases of both surfaces sometimes with papillose-based hairs, margins smooth or scabridulous. Panicles terminal and axillary, 2-5 cm long, 0.2-0.5 cm wide, contracted, cylindrical, included in the uppermost sheath; lower nodes with 1-2(3) branches; primary branches 0.4-1.8 cm, appressed, spikelet-bearing to the base; secondary branches appressed; pedicels 0.1-2.5 mm, appressed, scabridulous. Spikelets 1.6-3 mm, yellowish to cream-colored, sometimes purple-tinged. Glumes subequal, shorter than the florets, lanceolate to ovate, membranous to chartaceous, glabrous; lower glumes 1.5-2.4 mm, midveins often greenish; upper glumes 1.7-2.7 mm; lemmas 1.6-2.9 mm, ovate, chartaceous, glabrous, acute; paleas 1.6-3 mm, ovate, chartaceous, glabrous; anthers 3, 1.1-1.6 mm, purplish. Fruits 1.2-1.8 mm, obovoid, laterally flattened, light brownish or orangish-brown, translucent, finely striate. 2n = 36.

Sporobolus neglectus is native to the Flora region, and grows at 0-1300 m in sandy soils, on river shores, and in dry, open areas within many plant communities, often in disturbed sites. It appears to have been extirpated from Maine and Maryland and is considered endangered or of special concern in Connecticut, Massachusetts, New Hampshire, and New Jersey.

Sporobolus vaginiflorus is very similar to S. neglectus, but it differs in having strigose lemmas, sheaths that are sparsely hairy towards the base and, usually, longer spikelets.


6.   Sporobolus virginicus (L.) Kunth
Seashore Dropseed

Plants perennial; rhizomatous, stoloniferous. Culms 10-65 cm, erect to decumbent. Sheaths overlapping, margins ciliate, apices with tufts of hairs, hairs to 2 mm; ligules 0.1-0.4 mm; blades usually conspicuously distichous, 4-16 cm long, 2-5 mm wide, flat to loosely involute, glabrous abaxially, scabridulous adaxially, margins scabridulous. Panicles 3-10 cm long, 0.4-1.6 cm wide, contracted, spikelike, dense; primary branches 0.5-2 cm, appressed, spikelet-bearing to the base; pedicels 0.2-1.4 mm, appressed. Spikelets (1.8)2-3.2 mm, yellowish-white to purplish-tinged, sometimes grayish. Glumes subequal, ovate-oblong, membranous; lower glumes 1.5-2.4 mm; upper glumes 1.8-3(3.2) mm; lemmas 2.1-3 mm, ovate to lanceolate, membranous, glabrous, acute; paleas 2.1-3 mm, ovate, membranous; anthers 3, 1-1.7 mm, yellowish. Fruits not known. 2n = 20, 30.

Sporobolus virginicus grows on sandy beaches, sand dunes, and in saline habitats, primarily along the southeastern coast, occasionally inland. Its range extends through Mexico and Central America to Peru, Chile, and Brazil. No fruits of this species have been found despite examination of several natural populations and over 200 herbarium specimens.


7.   Sporobolus compositus (Poir.) Merr.
Rough Dropseed, Sporobole Rude

Plants perennial; cespitose, sometimes rhizomatous. Culms (20)30-130(150) cm. Sheaths with sparsely hairy apices, hairs to 3 mm; ligules 0.1-0.5 mm; blades not conspicuously distichous, 5-70 cm long, 1.5-10 mm wide, flat, folded, or involute, abaxial surface glabrous or pilose, adaxial surface glabrous or scabridulous, margins glabrous. Panicles terminal and axillary, 5-30 cm long, 0.4-1.6 cm wide, usually spikelike, partially included in the uppermost sheath, with 15-90 spikelets per cm2 (exposed portion, when pressed); lower nodes with 1-2(3) branches; primary branches 0.4-6 cm, appressed, spikelet-bearing to the base; secondary branches appressed; pulvini glabrous; pedicels 0.3-3.5 mm, appressed, glabrous or scabridulous. Spikelets 4-6(10) mm, stramineous to purplish-tinged. Glumes subequal, lanceolate, membranous to chartaceous, midveins usually greenish; lower glumes (1.2)2-4 mm; upper glumes (2)2.5-5(6) mm, slightly shorter or longer than the lemmas; lemmas (2.2)3-6(10) mm, lanceolate, membranous to chartaceous and hyaline, glabrous, smooth, occasionally 2- or 3-veined, acute to obtuse; paleas (2.2)3-6(10) mm, ovate to lanceolate, membranous; anthers 0.2-3.2 mm, yellow to orangish. Fruits 1-2 mm, ellipsoid, laterally flattened, often striate, reddish-brown; pericarps gelatinous, slipping from the seeds when wet. 2n = 54, 88, 108.

Sporobolus compositus grows along roadsides and railroad right of ways, on beaches, and in cedar glades, pine woods, live oak-pine forests, prairies, and other partially disturbed, semi-open sites at 0-1600 m. Its range lies entirely within the Flora region.

The Sporobolus compositus complex is a difficult assemblage of forms, perhaps affected by their primarily autogamous breeding system (Riggins 1977). Asexual proliferation via rhizomes adds to the species ability to maintain local population structure and to perpetuate unique character combinations.

1
Rhizomes present ..... var. macer
Rhizomes absent (2)
2
Culms slender, 1-2(2.5) mm thick; upper sheaths usually less than 2.5 mm wide; panicles with 16-36 spikelets per cm2 when pressed ..... var. drummondii
Culms stout, 2-5 mm thick; upper sheaths usually 2.6-6 mm wide; panicles with 30-90 spikelets per cm2 when pressed ..... var. compositus


Sporobolus compositus (Poir.) Merr. var. compositus

Plants not rhizomatous. Culms stout, 2-5 mm thick. Uppermost sheaths usually 2.6-6 mm wide. Panicles with 30-90 spikelets per cm2 when pressed. Fruits 1-1.8 mm.

Sporobolus compositus var. compositus is the most widespread of the three varieties, being found throughout most of the range shown for the species, but not in South Carolina or Florida.


Sporobolus compositus var. drummondii (Trin.) Kartesz & Gandhi

Plants not rhizomatous. Culms slender, 1-2(2.5) mm thick at the base. Uppermost sheaths 0.8-2.5 mm wide. Panicles with 16-36 spikelets per cm2 when pressed. Fruits 1.1-1.7 mm.

Sporobolus compositus var. drummondii is most abundant in Kansas, Oklahoma, and Texas.


Sporobolus compositus var. macer (Trin.) Kartesz & Gandhi

Plants rhizomatous. Culms slender, 0.7-2.2 mm thick at the base. Uppermost sheath 0.7-2.5 mm wide. Panicles with 15-42 spikelets per cm2 when pressed. Fruits 1.3-1.6 mm.

Sporobolus compositus var. macer is known only from the south central United States.


8.   Sporobolus clandestinus (Biehler) Hitchc.
Hidden Dropseed

Plants perennial; cespitose, occasionally rhizomatous. Culms 40-130(150) cm tall, 1-4 mm thick, frequently glaucous. Sheaths with sparsely hairy apices, hairs to 3 mm , not conspicuously tufted; uppermost sheaths 0.5-3 mm wide; ligules 0.1-0.4 mm; blades 4-23 cm long, 1.5-4 mm wide, flat or involute, abaxial surface glabrous or pilose, adaxial surface glabrous or scabridulous, margins glabrous. Panicles terminal and axillary, 5-11 cm long, 0.04-0.2(0.3) cm wide, with 10-40 spikelets per cm2, narrow, sometimes spikelike, included in the uppermost sheath; lower nodes with 1-2(3) branches; primary branches 0.4-5 cm, appressed, spikelet-bearing to the base; secondary branches appressed; pulvini glabrous; pedicels 0.3-3.5 mm, appressed, glabrous or scabridulous. Spikelets 4-9(10) mm, stramineous to purplish-tinged. Glumes subequal, lanceolate, membranous to chartaceous, midveins usually greenish; lower glumes 1.5-6.2 mm; upper glumes (2)2.5-5(6.5) mm, slightly shorter or longer than the lemmas; lemmas (2.2)3-7(7.4) mm, lanceolate, chartaceous and opaque, minutely appressed pubescent or scabridulous, occasionally 2- or 3-veined, acute to obtuse; paleas (2.2)3-9(10) mm, ovate to lanceolate, chartaceous; anthers 2.2-3.2 mm, yellow to orangish. Fruits (1.5)2.4-3.5 mm, ellipsoid, laterally flattened, often striate, reddish-brown; pericarps loose, but neither gelatinous nor slipping from the seeds when wet. 2n = unknown.

Sporobolus clandestinus grows primarily in sandy soils along the coast and, inland, along roadsides. In the southeastern United States, it is found in dry to mesic longleaf pine-oak-grass communities and cedar glades. Its range lies entirely within the Flora region.


9.   Sporobolus indicus (L.) R. Br.
Smutgrass

Plants perennial; cespitose, with tough fibrous roots, not rhizomatous. Culms 30-100(120) cm. Sheaths usually keeled below, glabrous; ligules 0.2-0.5 mm; blades (6)10-30(50) cm long, 1-5 mm wide, flat, glabrous on both surfaces. Panicles 20-35(50) cm long, 0.3-2.2(3) cm wide, contracted, narrow, sometimes included in the uppermost sheath; primary branches 0.4-2.5(5) cm, appressed or spreading to 40° from the rachis, as long or longer than the adjacent internodes; secondary branches appressed, spikelet-bearing to near the base; pulvini glabrous; pedicels 0.1-1.8 mm, appressed. Spikelets 2-2.6(2.7) mm, plumbeous to light brownish. Glumes subequal, ovate or obovate, membranous; lower glumes 0.5-1 mm, often without midveins; upper glumes 0.8-1.6 mm, 1/2-2/3 as long as the florets, acute to obtuse, entire; lemmas 1.8-2.6(2.7) mm, ovate, membranous, glabrous, acute or obtuse; paleas 1.9-2.4 mm, ovate, membranous, glabrous; anthers 3, 0.5-1.1 mm, white, sometimes purple-tinged. Fruits 1-1.2 mm, quadrangular, laterally compressed, reddish-brown, truncate. 2n = 18, 24, 36.

Sporobolus indicus is a pantropical species. It commonly grows in disturbed places and open areas such as roadsides, pastures, and lake shores. In the Flora region, it is found on sandy or clay soils and is associated with many plant communities. The spikelets and upper leaves are often covered with hyphomycetous fungi (Bipolaris spp.); hence the common name of 'smutgrass'.


10.   Sporobolus jacquemontii Kunth
Ratstail

Plants perennial; densely cespitose, not rhizomatous. Culms 40-100 cm. Sheaths keeled or rounded, glabrous, apices ciliate; ligules 0.2-0.4 mm; blades 10-40 cm long, 2-4 mm wide, flat but soon becoming involute, tapering to a fine point. Panicles 14-35 cm long, 0.4-3 cm wide, contracted, interrupted, and rather lax; primary branches appressed to strongly ascending, spikelet-bearing to the base, lower branches 1.5-5 cm, much longer than the adjacent internodes; pedicels 0.1-1.2(1.8) mm. Spikelets 1.4-1.8(2) mm, plumbeous to greenish. Lower glumes 0.3-0.5 mm, obtuse; upper glumes 0.4-0.7 mm, usually less than 1/2 as long as the florets, faintly 1-veined, truncate, erose to denticulate; lemmas 1.4-2 mm, elliptic, glabrous, 1-veined, acute; paleas 1.4-2 mm, elliptic; anthers 3(2), 0.9-1.1 mm. Fruits 0.7-1 mm, quadrangular, laterally compressed, reddish-brown, truncate. 2n = 24.

Sporobolus jacquemontii, like S. indicus, is native to North America. It is not a common species in the Flora region, being known only from coastal and low elevation sites in Florida. It is sometimes included in S. indicus (Baaijens and Veldkamp 1991) or S. pyramidalis P. Beauv. (Laegaard and Peterson 2001), but is retained here pending more definitive study.


11.   Sporobolus creber De Nardi

Plants perennial; densely cespitose, not rhizomatous. Culms 6.5-100 cm. Sheaths rounded, margins ciliate, apices with tufts of hairs to 2 mm; ligules about 0.5 mm, the sides with a few hairs to 1.5 mm; blades 7-30 cm long, 1-2(3) mm wide, flat, becoming involute, tapering to a fine point. Panicles 20-40 cm long, 0.4-1 cm wide, narrowly contracted, sometimes spikelike; primary branches appressed to strongly ascending, spikelet-bearing to the base, lower branches 1.5-3 cm, much shorter than the adjacent internodes, usually appressed; pedicels 0.1-0.5 mm. Spikelets 1.1-1.5 mm, dark green. Glumes obtuse, often erose; lower glumes 0.4-0.5 mm; upper glumes 0.5-0.6 mm, less than 2/3 as long as the florets; lemmas 1.1-1.5 mm, glabrous, 1-veined, obtuse; paleas similar to the lemmas or slightly longer; anthers 2, 0.4-0.6 mm. Fruits 0.7-0.8 mm, often adhering to the floret at maturity, quadrangular to somewhat turbinate, red-brown, apices truncate and concave. 2n = unknown.

Sporobolus creber is an Australian species that was recently found growing spontaneously on a ranch in Glenn County, California. It is related to S. indicus, but differs in its widely spaced, closely appressed, and densely spikeleted branches.


12.   Sporobolus diandrus (Retz.) P. Beauv.

Plants perennial; cespitose, not rhizomatous. Culms 30-80 cm. Sheaths keeled or rounded; ligules 0.2-0.5 mm; blades 10-30 cm long, 2-4 mm wide, flat, becoming folded. Panicles 15-35 cm long, 0.4-4 cm wide, contracted to rather lax and open; primary branches appressed to strongly ascending, without spikelets on the lower 1/4, lower branches much longer than the internodes; pedicels 0.1-3 mm. Spikelets 1.3-1.8 mm, plumbeous to greenish. Lower glumes 0.4-0.8 mm, acuminate to truncate; upper glumes 0.7-1 mm, usually less than 1/2 as long as the florets, rarely longer, faintly 1-veined, truncate, erose to denticulate; lemmas 1.2-1.6(1.8) mm, elliptic, glabrous, 1-veined, acute to obtuse; paleas 1.4-1.8 mm, elliptic; anthers 2(3), 0.5-0.8 mm. Fruits 0.7-0.9 mm, quadrangular, laterally compressed, reddish-brown, truncate. 2n = 12.

Sporobolus diandrus is native from India to southeast Asia and Australia. It is not common in North America, being known only from a few counties in Florida, Mississippi, and Texas.


13.   Sporobolus fimbriatus (Trin.) Nees

Plants perennial; rhizomatous. Culms 30-120(160) cm. Sheaths rounded and papery below; ligules 0.1-0.3 mm; blades 10-30 cm long, 2-4(5) mm wide, not obviously distichous, flat, becoming folded, pilose abaxially, tapering to the slender apices. Panicles 15-50 cm long, 2.4-8 cm wide, somewhat contracted to rather lax and open; primary branches appressed or ascending, spreading to 60° from the rachis; spikelet-bearing to the base or without spikelets on the lower 1/4, lower branches mostly 2-9 cm, longer than the internodes; pedicels 0.7-3 mm. Spikelets 1.4-2.2 mm, plumbeous to greenish. Glumes unequal, linear-lanceolate to ovate, membranous; lower glumes (0.4)0.6-1.2(1.5) mm, without midveins, acuminate; upper glumes (0.9)1.4-2 mm, 2/3 to as long as the spikelet, faintly 1-veined, acute; lemmas (1.4)1.8-2.2 mm, narrowly ovate, glabrous, 1-veined, acute; paleas (1.2)1.6-2 mm, ovate; anthers 3, 09-1.2 mm. Fruits 0.6-1 mm, quadrangular, laterally compressed, whitish-brown, truncate. 2n = unknown.

Sporobolus fimbriatus is an African species that has only been found in waste areas near the sites of old wool mills in Berkeley and Florence counties, South Carolina.


14.   Sporobolus buckleyi Vasey
Buckley's Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 40-100 cm. Sheaths keeled and flattened below, margins occasionally hairy distally, hairs to 1.2 mm; ligules 0.2-0.4 mm; blades 12-35 cm long, 4-12 mm wide, flat, glabrous abaxially, scabridulous adaxially, margins smooth or scabridulous. Panicles 15-50 cm long, 7-22(30) cm wide, diffuse, ovate; primary branches 2-17 cm, spreading 40-100° from the rachis; secondary branches appressed to loosely spreading, without spikelets on the lower 1/4-1/2; pulvini glabrous; pedicels 0.2-1.2 mm, appressed, scabridulous. Spikelets 1-2 mm, purplish to brownish. Glumes unequal, narrowly lanceolate to lanceolate, membranous, prominently keeled; lower glumes 0.6-1 mm; upper glumes 1.1-1.8 mm, slightly shorter than or subequal to the lemmas; lemmas 1.2-2 mm, lanceolate, membranous, glabrous, acute; paleas 1.2-2 mm, ovate, membranous, glabrous, often splitting in two between the veins at maturity; anthers 0.2-0.4 mm, purplish. Fruits 0.6-1 mm, ovoid, slightly flattened, reddish-brown. 2n = 40.

Sporobolus buckleyi grows between 0-150 m, in loamy soils near the margins of woods or thorn scrub, sometimes in partial sunlight. Its range extends from southeastern Texas to Belize.


15.   Sporobolus domingensis (Trin.) Kunth
Coral Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 20-100 cm. Sheaths rounded below, distal margins and apices hairy, hairs to 3 mm; ligules 0.2-1.2 mm; blades 5-20 cm long, 3-8 mm wide, flat to loosely involute, glabrous abaxially, scabridulous adaxially, margins scabridulous. Panicles 10-25(35) cm long, 1-5 cm wide, usually somewhat contracted, sometimes spikelike, often interrupted below; primary branches 0.7-7 cm, appressed or spreading to 30° from the rachis, spikelet-bearing to the base; secondary branches appressed; pedicels 0.2-1.4 mm, appressed. Spikelets 1.6-2 mm, yellowish-green to grayish. Glumes unequal, linear-lanceolate to ovate, membranous; lower glumes 0.5-1.1 mm, usually without veins; upper glumes 1.1-2 mm, subequal to the lemmas; lemmas 1.1-2 mm, ovate, membranous, glabrous (occasionally minutely pubescent), acute; paleas 1-2 mm, ovate, membranous; anthers 2 or 3, 0.5-1 mm, yellowish or purplish. Fruits 0.7-1.1 mm, ellipsoid, laterally flattened, light brownish. 2n = unknown.

Sporobolus domingensis grows in sandy, rocky, or alkaline soils, often in disturbed sites adjacent to the coast and below 20 m. Its range extends to the Antilles and the Yucatan Peninsula, Mexico.


16.   Sporobolus wrightii Munro ex Scribn.
Big Alkali Sacaton

Plants perennial; cespitose, not rhizomatous. Culms 90-250 cm, stout. Sheaths rounded below, shiny, glabrous, rarely sparsely hairy apically, hairs to 6 mm; ligules 1-2 mm; blades 20-70 cm long, 3-10 mm wide, flat (rarely involute), glabrous abaxially, scabrous adaxially, margins scabrous; flag blades ascending. Panicles 20-60 cm long, 12-26 cm wide, open, broadly lanceolate, exserted; primary branches 1.5-10 cm, spreading 20-70° from the rachis; secondary branches appressed, spikelet-bearing to the base; pulvini glabrous; pedicels 0.2-0.5 mm, mostly appressed. Spikelets 1.5-2.5 mm, crowded, purplish or greenish. Glumes unequal, lanceolate to ovate, membranous; lower glumes 0.5-1 mm, often appearing veinless; upper glumes 0.8-2 mm, 2/3 or more as long as the florets; lemmas 1.2-2.5 mm, ovate, membranous, glabrous, acute to obtuse; paleas 1.1-2.5 mm, ovate, membranous, glabrous; anthers 1.1-1.3 mm, yellowish to purplish. Fruits 1-1.4 mm, ellipsoid, reddish-brown or blackish, striate. 2n = 36.

Sporobolus wrightii grows in moist clay flats and on rocky slopes near saline habitats, at elevations of 5-1800 m. Its range extends to central Mexico.


17.   Sporobolus airoides (Torr.) Torr.
Alkali Sacaton

Plants perennial; cespitose, not rhizomatous. Culms 35-120(150) cm, stout. Sheaths rounded below, shiny, apices glabrous or sparsely hairy, hairs to 6 mm; ligules 0.1-0.3 mm; blades (3)10-45(60) cm long, (1)2-5(6) mm wide, flat to involute, glabrous abaxially, scabridulous adaxially, margins smooth or scabridulous; flag blades ascending. Panicles (10)15-45 cm long, 15-25 cm wide, diffuse, subpyramidal, often included in the uppermost sheath; primary branches 1.5-13 cm, spreading 30-90° from the rachis; secondary branches spreading, without spikelets on the lower 1/4-1/3; pulvini glabrous; pedicels 0.5-2 mm, spreading, glabrous or scabrous. Spikelets 1.3-2.8 mm, purplish or greenish. Glumes unequal, lanceolate to ovate, membranous; lower glumes 0.5-1.8 mm, often without midveins; upper glumes 1.1-2.4(2.8) mm, at least 2/3 as long as the florets; lemmas 1.2-2.5 mm, ovate, membranous, glabrous, acute; paleas 1.1-2.4 mm, ovate, membranous, glabrous; anthers 1.1-1.8 mm, yellowish to purplish. Fruits 1-1.4 mm, ellipsoid, reddish-brown, striate. 2n = 80, 90, 108, 126.

Sporobolus airoides grows on dry, sandy to gravelly flats or slopes, at elevations from 50-2350 m. It is usually associated with alkaline soils. Its range extends into northern Mexico.


18.   Sporobolus cryptandrus (Torr.) A. Gray
Sand Dropseed, Sporobole à Fleures Cachées

Plants perennial; cespitose, not rhizomatous, bases not hard and knotty. Culms 30-100(120) cm tall, 1-3.5 mm thick, erect to decumbent. Sheaths rounded below, glabrous or scabridulous, margins sometimes ciliate distally, apices with conspicuous tufts of hairs, hairs to 4 mm; ligules 0.5-1 mm; blades (2)5-26 cm long, 2-6 mm wide, flat to involute, glabrous abaxially, scabridulous to scabrous adaxially, margins scabridulous; flag blades nearly perpendicular to the culms. Panicles 15-40 cm long, 2-12(14) cm wide, longer than wide, initially contracted and spikelike, ultimately open and narrowly pyramidal; rachises straight, erect; lower nodes with 1-2(3) branches; primary branches 0.6-6 cm, appressed, spreading, or reflexed to 130° from the rachis, without spikelets on the lower 1/8-1/4, lower branches longest, included in the uppermost sheath; secondary branches appressed; pulvini glabrous; pedicels 0.1-1.3 mm, appressed, glabrous or scabridulous. Spikelets 1.5-2.5(2.7) mm, brownish, plumbeous, or purplish-tinged. Glumes unequal, linear-lanceolate to ovate, membranous; lower glumes 0.6-1.1 mm; upper glumes 1.5-2.7 mm, at least 2/3 as long as the florets; lemmas 1.4-2.5(2.7) mm, ovate to lanceolate, membranous, glabrous, acute; paleas 1.2-2.4 mm, lanceolate, membranous; anthers 0.5-1 mm, yellowish to purplish. Fruits 0.7-1.1 mm, ellipsoid, light brownish to reddish-orange. 2n = 36, 38, 72.

Sporobolus cryptandrus is a widespread North American species, extending from Canada into Mexico. It grows in sandy soils and washes, on rocky slopes and calcareous ridges, and along roadsides in salt-desert scrub, pinyon-juniper woodlands, yellow pine forests, and desert grasslands. Its elevational range is 0-2900 m.


19.   Sporobolus contractus Hitchc.
Spike Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 40-100(120) cm tall, 2-4(5) mm thick near the base. Sheaths rounded below, margins hairy, particularly distally, hairs to 3 mm, apices with conspicuous tufts of hair; ligules 0.4-1 mm; blades (2)4-35 cm long, 3-8 mm wide, flat to involute, glabrous on both surfaces, margins whitish, somewhat scabridulous. Panicles all terminal, (10)15-45(50) cm long, 0.2-0.8(1) cm wide, contracted, spikelike, dense, usually included in the uppermost sheath; lower nodes with 1-2(3) branches; primary branches 0.3-1.5 cm, appressed, spikelet-bearing to the base; secondary branches appressed; pulvini glabrous; pedicels 0.2-2 mm, appressed, scabridulous. Spikelets 1.7-3.2 mm, whitish to plumbeous. Glumes unequal, narrowly lanceolate, membranous, prominently keeled; lower glumes 0.7-1.7 mm, usually 1-veined, acute to acuminate; upper glumes 2-3.2 mm, at least 2/3 as long as the florets; lemmas 2-3.2 mm, linear-lanceolate, membranous, glabrous, acute; paleas 1.8-3 mm, linear-lanceolate, membranous, glabrous; anthers 3, 0.3-0.5 mm, light yellowish. Fruits 0.8-1.2 mm, ellipsoid, laterally flattened, light brownish or translucent. 2n = 36.

Sporobolus contractus grows in dry to moist, sandy soils, at elevations from 300-2300 m. It is found occasionally in salt-desert scrub, desert grasslands, and pinyon-juniper woodlands. Its range extends to the states of Baja California and Sonora in Mexico.


20.   Sporobolus texanus Vasey
Texas Dropseed

Plants perennial (often appearing annual); cespitose, with fibrous roots, not rhizomatous. Culms 20-70 cm, erect to decumbent, glabrous or scurfy roughened below. Sheaths rounded basally, apices glabrous or with scattered, appressed, papillose-based hairs, hairs to 4 mm; ligules 0.2-0.6 mm; blades 2.5-13(18) cm long, 1-4.2 mm wide, flat to involute, glabrous abaxially, scabrous adaxially, margins scabridulous, often also with a few papillose-based hairs; flag blades ascending. Panicles 10-35 cm long, 4.5-30 cm wide, open, diffuse, subpyramidal, about as long as wide, partially included in the uppermost leaf sheath; lower nodes with 1-2 branches; primary branches 4-14 cm, capillary, spreading 10-80° from the rachis; secondary branches spreading, without spikelets on the lower 1/3-1/2; pedicels 6-25 mm, spreading. Spikelets 2.3-3 mm, purplish-tinged. Glumes unequal, linear-lanceolate to lanceolate, membranous; lower glumes 0.5-1.7 mm, often without midveins; upper glumes 1.7-3 mm, at least 2/3 as long as the florets, often longer; lemmas 1.8-3 mm, lanceolate to ovate, membranous, glabrous, acute; paleas 1.7-2.9 mm, ovate, membranous, glabrous, often splitting as the fruit matures; anthers 0.3-1 mm, yellowish. Fruits1.1-1.5 mm, obovoid, light brown, translucent, occasionally rugulose. 2n = unknown.

Sporobolus texanus grows along rivers, ponds, and in wet alkaline habitats, at 100-3300 m. It is known only from the United States.


21.   Sporobolus nealleyi Vasey
Gypgrass

Plants perennial; cespitose, bases hard and knotty, not rhizomatous. Culms10-50(60) cm tall, 0.7-1.2 mm thick. Sheaths rounded below, occasionally glabrous, usually villous to tomentose along the margins and back, with soft, kinky hairs to 4 mm; ligules 0.2-0.4 mm; blades (0.6)1.5-6(7) cm long, 1-1.5 mm wide, involute, stiff, spreading at right angles to the culm, glabrous abaxially, scabridulous adaxially, margins smooth. Panicles 3-10 cm long, (0.3)1-5(6) cm wide, longer than wide, ultimately open, subovate, lower portion often included in the uppermost sheath; lower nodes with 1-2 branches; primary branches 0.5-5 cm, appressed or spreading to 90° from the rachis; secondary branches appressed or spreading, without spikelets on the lower 1/8-1/4; pedicels 0.2-2 mm, appressed or spreading. Spikelets 1.4-2.1 mm, purplish. Glumes unequal, linear-lanceolate to ovate, membranous; lower glumes 0.5-1.1 mm; upper glumes 1.3-2 mm, from slightly shorter than to subequal to the florets; lemmas 1.4-2.1 mm, ovate, membranous, glabrous, acute; paleas 1.4-2.1 mm, ovate, membranous; anthers 0.7-1 mm, purplish. Fruits 0.7-1 mm, orangish to whitish. 2n = 40.

Sporobolus nealleyi grows in sandy and gravelly soils, usually in those derived from gypsum, or near alkaline habitats associated with desert grasslands. It is known only from the southwestern United States, where it grows at 700-3000 m.


22.   Sporobolus flexuosus (Thurb. ex Vasey) Rydb.
Mesa Dropseed

Plants perennial (rarely appearing annual); cespitose, not rhizomatous, bases not hard and knotty. Culms 30-100(120) cm tall, 1-3 mm thick near the base, erect to decumbent. Sheaths rounded below, smooth or scabridulous, margins sometimes ciliate distally, apices with tufts of hairs, hairs to 4 mm; ligules 0.5-1 mm; blades (2)5-24 cm long, 2-4(6) mm wide, ascending or strongly divergent, flat to involute, glabrous abaxially, scabridulous adaxially, margins scabridulous. Panicles 10-30 cm long, 4-12 cm wide, longer than wide, open, subovate to oblong; rachises drooping or nodding; lower nodes with 1-2 branches; primary branches 1-8(12) cm, flexible, diverging at least 70° from the rachis, often strongly reflexed to 130° , tangled with each other and with branches from adjacent panicles, lower branches no longer than those in the middle, usually included in the uppermost sheath; secondary branches widely spreading, without spikelets on the lower 1/8-1/2; pulvini pubescent; pedicels 0.3-3 mm, spreading, scabridulous. Spikelets 1.8-2.5 mm, plumbeous. Glumes unequal, ovate, membranous; lower glumes 0.9-1.5 mm; upper glumes 1.4-2.5 mm, subequal to the florets; lemmas 1.4-2.5 mm, lanceolate to ovate, membranous, glabrous, acute; paleas 1.4-2.4 mm, ovate, membranous; anthers 0.4-0.7 mm, yellow. Fruits 0.6-1 mm, ellipsoid, light brownish to reddish-orange. 2n = 36, 38.

Sporobolus flexuosus grows on sandy to gravelly slopes, flats, and roadsides in the southwestern United States and northern Mexico. It is associated with desert scrub, pinyon-juniper woodlands, and yellow pine forests. Its elevational range is 800-2100 m.


23.   Sporobolus giganteus Nash
Giant Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 100-200 cm, (3)4-10 mm thick near the base. Sheaths rounded below, striate, margins hairy distally, apices with conspicuous tufts of hairs, hairs to 2 mm; ligules 0.5-1.5 mm; blades 10-50 cm long, (3)4-10(13) mm wide, flat, glabrous on both surfaces, margins whitish, scabridulous. Panicles all terminal, 25-75 cm long, 1-4 cm wide, spikelike, dense, usually included in the uppermost sheath; lower nodes with 1-2(3) branches; primary branches mostly 0.5-6 cm, appressed or spreading to 30° from the rachis, spikelet-bearing to the base; secondary branches appressed; pulvini glabrous; pedicels 0.5-2 mm, appressed. Spikelets 2.5-3.5(4) mm, whitish to plumbeous. Glumes unequal, narrowly lanceolate, membranous, prominently keeled; lower glumes 0.6-2 mm; upper glumes 2-3.5(4) mm, subequal to the lemmas; lemmas 2.5-3.5(4) mm, linear-lanceolate, membranous, glabrous, acute; paleas 2.4-3.4(3.8) mm, linear-lanceolate, membranous, glabrous; anthers 0.6-1 mm, yellowish. Fruits 0.8-1.7 mm, ellipsoid, light yellowish-brown, sometimes translucent. 2n = 36.

Sporobolus giganteus grows in sand dunes and sandy areas along rivers and roadsides, at elevations from 100-1830 m. Its range extends from the southwestern United States into northern Mexico.


24.   Sporobolus junceus (P. Beauv.) Kunth
Piney-Woods Dropseed

Plants perennial; cespitose, not rhizomatous. Culms (30)40-100 cm. Sheaths rounded below, margins and apices sometimes sparsely ciliate; ligules 0.1-0.2 mm; blades (6)10-30 cm long, 0.8-2 mm wide, flat to tightly involute, glabrous abaxially, scabridulous adaxially, margins scabrous, apices pungent. Panicles 7-28 cm long, 2-6 cm wide, open, pyramidal; lower nodes with 3 or more branches; primary branches 0.7-4.5 cm, spreading 20-100° from the rachis, whorled or verticellate, without spikelets on the lower 1/8-1/2; secondary branches appressed; pedicels 0.4-2.5 mm, appressed, scabridulous. Spikelets 2.6-3.8 mm, purplish-red. Glumes unequal, linear-lanceolate to lanceolate or ovate, hyaline to membranous; lower glumes 0.9-3 mm; upper glumes 2.6-3.8 mm, as long as or longer than the florets; lemmas 2-3.6 mm, ovate, membranous, glabrous, acute; paleas 2-3.6 mm, ovate, membranous; anthers 1.4-2 mm, purplish. Fruits 1.4-1.8 mm, ellipsoid, somewhat laterally flattened, somewhat rugulose, reddish-brown. 2n = unknown.

Sporobolus junceus grows in openings in pine and hardwood forests, coastal prairies, and pine barrens, usually in sandy to loamy soils, at 2-400 m. Its range lies entirely within the southern United States.


25.   Sporobolus purpurascens (Sw.) Ham.
Purple Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 25-95 cm. Sheaths rounded below, upper margins sometimes sparsely hispid-ciliate, apices hairy, hairs to 5 mm; ligules 0.2-0.3 mm; blades 8-22 cm long, 2-5 mm wide, flat or involute, glabrous abaxially, scabridulous adaxially, margins scabrous, sometimes sparsely hispid. Panicles 5-30 cm long, 0.4-1.6 cm wide, narrow, contracted; lower nodes with 3 or 5 branches; primary branches 0.3-2 cm, appressed or spreading to 20° from the rachis, spikelet-bearing to near the base; secondary branches appressed; pedicels 0.2-2.5 mm, appressed, scabridulous. Spikelets 2.8-3.8 mm, purplish-red. Glumes unequal, linear-lanceolate to lanceolate or ovate, hyaline to membranous; lower glumes 0.9-3 mm; upper glumes 2.9-3.8 mm, subequal to the florets; lemmas 2.9-3.8 mm, ovate, membranous, glabrous, acute; paleas 2.9-3.8 mm, ovate, membranous; anthers 1.5-2 mm, yellowish to purplish. Fruits 1.8-2.3 mm, ellipsoid, somewhat laterally flattened, rugulose, reddish-brown. 2n = 60.

Sporobolus purpurascens grows in oak scrub, prairie grasslands, and sandy sites near railroad crossings and roadsides, at elevations from 2-300 m. It extends from southern Texas through eastern Mexico, the West Indies, and Central America to Brazil.


26.   Sporobolus interruptus Vasey
Black Dropseed

Plants perennial; cespitose but shortly rhizomatous, with tough, fibrous roots. Culms 25-60 cm. Sheaths dull and fibrous basally, with scattered, contorted hairs to 5 mm, margins glabrous; ligules 0.2-0.7 mm; blades (5)8-20 cm long, 1-2.5 mm wide, flat to folded, glabrous or scattered-pilose on both surfaces, margins glabrous. Panicles 5-20 cm long, (0.6)1-8 cm wide, longer than wide, narrowly pyramidal, open to somewhat contracted, not diffuse, well-exserted from the upper leaf sheath; lower nodes with 1-2(3) branches; primary branches 0.6-7 cm, appressed or spreading to 70° from the rachis, not capillary, without spikelets on the lower 1/3; pedicels 0.8-5.5 mm, appressed to spreading. Spikelets 4.5-6.6 mm, plumbeous. Glumes unequal, lanceolate, membranous; lower glumes (2)2.5-4.2 mm; upper glumes 3.8-6.5 mm, at least 2/3 as long as the florets; lemmas 5-6.5 mm, ovate, membranous, glabrous, acute; paleas 4.8-6.5 mm, ovate, membranous; anthers 3-4.2 mm, yellow to purplish. Fruits about 3 mm long, 1.5-1.7 mm thick, pyriform-globose; embryo dark brown to blackish; endosperm reddish-brown. 2n = 30.

Sporobolus interruptus grows on rocky slopes and in dry meadows of open yellow pine and oak-pine forests and pinyon-juniper woodlands, at elevations from 1500-2300 m. It is an Arizonan endemic that is morphologically similar to S. heterolepis, but the two species are separated geographically, the range of the latter lying to the north and east of Arizona. The only reliable morphological difference between them is anther length (3-4.2 mm long in S. interruptus, 1.7-3 mm long in S. heterolepis). Cytologically, S. interruptus appears to be triploid, while S. heterolepis appears to be an octoploid (2n = 72).


27.   Sporobolus heterolepis (A. Gray) A. Gray
Prairie Dropseed, Sporobole à Glumes Inégales

Plants perennial; cespitose, not rhizomatous. Culms 30-80(90) cm. Sheaths dull and fibrous basally, glabrous or sparsely pilose below, hairs to 4 mm, contorted; ligules 0.1-0.3 mm; blades 7-31 cm long, 1.2-2.5 mm wide, flat to folded, glabrous abaxially, scabridulous adaxially, margins scabrous. Panicles 5-22(25) cm long, (0.6)1-11 cm wide, open to somewhat contracted, longer than wide, narrowly pyramidal, not diffuse; lower nodes with 1-2(3) branches; primary branches 0.6-8(11) cm, appressed or spreading to 70° from the rachis, not capillary, without spikelets on the lower 1/3; pedicels 0.8-6 mm, appressed, occasionally spreading. Spikelets 3-6 mm, plumbeous. Glumes unequal, lanceolate, membranous; lower glumes (1.2)1.8-4.5 mm; upper glumes 2.4-6 mm, at least 2/3 as long as the florets, occasionally 3-veined; lemmas (2.7)3-4.3 mm, ovate, membranous, glabrous, acute; paleas 3.1-4.5 mm, slightly longer than the lemmas, ovate, membranous, glabrous; anthers 1.7-3 mm, yellowish to purplish. Fruits 1.4-2.1 mm, pyriform to globose, indurate, without a loose pericarp, smooth, shining, light brown. 2n = 72.

Sporobolus heterolepis grows at elevations of 40-2250 m, in lowland and upland prairies, along the borders of woods, roadsides, and swamps, and in north-facing swales. It is associated with many plant communities, and is also available commercially as an ornamental. It is restricted to the Flora region.


28.   Sporobolus teretifolius R.M. Harper
Wireleaf Dropseed

Plants perennial; cespitose, not rhizomatous. Culms (20)35-80(100) cm, wiry. Sheaths shiny and indurate basally, glabrous or appressed hairy elsewhere, hairs to 4 mm; ligules 0.2-0.4 mm; blades (10)25-54 cm long, 0.5-1.2 mm wide, terete or subterete at least basally, sometimes channeled for portions of their length, green to yellowish-green, senescing or turning tan in late fall, glabrous on both surfaces or the adaxial surface sparsely hairy basally, margins smooth. Panicles 10-26 cm long, 1-9 cm wide, open (contracted when immature), not diffuse, narrowly pyramidal to ovate; lower nodes with 1-2(3) branches; primary branches 1-8 cm, ascending or spreading to 40° from the rachis, not capillary, without spikelets on the lower 1/3; secondary branches spreading; pulvini hairy; pedicels 3-18 mm, longer than the spikelets, spreading, with scattered ascending hairs. Spikelets 4-5.6 mm, purplish-brown. Glumes unequal, linear-lanceolate, membranous; lower glumes 2-3.8 mm, 0.5-0.8 times as long as the upper glumes; upper glumes 4-5.6 mm, usually longer than the florets; lemmas 3.4-4.4 mm, ovate, membranous, glabrous, acute; paleas 3.3-4.4 mm, ovate, membranous, glabrous; anthers 1.5-2.6 mm, purplish. Fruits not seen. 2n = unknown.

Sporobolus teretifolius is restricted to the southeastern United States, where it grows in wet to moist flatwoods and savannahs, at elevations of 10-150 m.


29.   Sporobolus curtissii Small ex Kearney
Curtiss' Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 30-80(90) cm. Sheaths shiny and indurate basally, glabrous or appressed hairy elsewhere, hairs to 4 mm; ligules 0.2-0.6 mm; blades 5-22(28) cm long, 0.8-2(2.2) mm wide, flat to V-shaped in cross section, folded or involute when dry, green, remaining so well into winter, glabrous abaxially, mostly glabrous adaxially but densely pilose basally, margins glabrous or scabridulous. Panicles 10-25 cm long, 2-10(13) cm wide, longer than wide, open (contracted when immature), not diffuse, pyramidal to ovate; lower nodes with 1-2(3) branches; primary branches 2-9(10) cm, ascending or spreading to 80° from the rachis, not capillary, without spikelets on the lower 1/3; secondary branches mostly appressed; pulvini glabrous or hairy; pedicels 0.5-4(8) mm, usually shorter than the spikelets, appressed, glabrous. Spikelets 3.5-6.6 mm, purplish-brown. Glumes equal to subequal, linear-lanceolate, membranous; lower glumes (2.9)3.5-6.2 mm, 0.9-1.2(1.3) times as long as the upper glumes; upper glumes 3.2-6.6 mm, from almost as long as to longer than the florets; lemmas 3.4-4.5 mm, ovate to lanceolate, membranous, glabrous, acute; paleas 3.4-4.5 mm, ovate, membranous, glabrous; anthers 1.5-2.8 mm, yellow to purplish. Fruits 1.1-1.4 mm, fusiform, reddish-brown. 2n = unknown.

Sporobolus curtissii is restricted to the southeastern United States, where it grows in dry-mesic to moist flatwoods, in soils seasonally saturated at the surface or rather well-drained throughout the year. Its elevational range is 0-100 m.


30.   Sporobolus silveanus Swallen
Silveus' Dropseed

Plants perennial; cespitose, not rhizomatous. Culms 70-120 cm. Sheaths shiny and indurate basally, glabrous or appressed hairy elsewhere, hairs to 4 mm; ligules 0.2-0.8 mm; blades 15-52 cm long, 1-2.5 mm wide, flat, folded or involute, bluish-green, remaining so well into winter, glabrous on both surfaces, margins scabridulous. Panicles 21-50 cm long, 5-12(15) cm wide, longer than wide, open, not diffuse, pyramidal to ovate, with few spikelets; lower nodes with 1-2(3) branches; primary branches 6-20 cm, ascending, spreading 20-50° from the rachis, not capillary, without spikelets on the lower 1/4-1/2; secondary branches appressed to loosely spreading; pulvini glabrous; pedicels 3-8(14) mm, longer or shorter than the spikelets, appressed, glabrous, scabrous. Spikelets 4.5-7(7.2) mm, purplish. Glumes subequal to unequal, linear-lanceolate to lanceolate, membranous; lower glumes 3-4.6 mm, 0.6-0.9 times as long as the upper glumes; upper glumes 4-7.2 mm, from slightly shorter to longer than the spikelets; lemmas 4.4-6.5 mm, lanceolate, membranous, glabrous, acuminate to acute; paleas 4.5-6.7 mm, lanceolate, membranous, glabrous; anthers 3, 3.5-5 mm, purplish. Fruits 1.8-2.2 mm, obovoid, laterally flattened, light brownish. 2n = unknown.

Sporobolus silveanus is restricted to the southeastern United States. It grows in wet to mesic pine woodlands and adjoining glades and barren openings, and in blackland prairies, at elevations of 5-200 m.


31.   Sporobolus floridanus Chapm.
Florida Dropseed

Plants perennial; cespitose, not rhizomatous. Culms (40)100-200(250) cm. Sheaths shiny and indurate basally, glabrous or appressed hairy elsewhere, hairs to 5 mm; ligules 0.2-0.7 mm; blades (10)25-50 cm long, (2)3-10 mm wide, flat to folded, pale bluish-green, yellowing at maturity, glabrous on both surfaces or the adaxial surface sparsely hairy basally, margins scabridulous. Panicles (18)30-50 cm long, 4-15 cm wide, open (contracted when immature), longer than wide, not diffuse, pyramidal to ovate; lower nodes with 1-2(3) branches; primary branches 4-15 cm, spreading 10-90° from the rachis, not capillary, without spikelets on the lower 1/3; secondary branches spreading; pulvini hairy or glabrous; pedicels 2-14 mm, longer than the spikelets, spreading, glabrous, sometimes scabridulous. Spikelets (3.7)4-6 mm, purplish-brown. Glumes linear-lanceolate, membranous; lower glumes 2.5-5.1 mm, (0.6)0.75-0.9(0.94) times as long as the upper glumes; upper glumes 3.7-5.7 mm, longer than the florets; lemmas 3-4 mm, ovate to lanceolate, membranous, glabrous, acute; paleas 3-4 mm, ovate, membranous, glabrous; anthers 2-3.1 mm, purplish. Fruits 1.7-2 mm, fusiform, reddish-brown. 2n = unknown.

Sporobolus floridanus grows in wet to mesic pine woodlands, seepage bogs, and treeless swales, in soils semi-permanently to seasonally saturated at the surface, and in places where water may pond for weeks, at elevations of 0-100 m. It is endemic to the southeastern United States.


32.   Sporobolus pinetorum Weakley & P.M. Peterson
Carolina Dropseed

Plants perennial; cespitose, not rhizomatous. Culms (30)45-120(180) cm. Sheaths shiny and indurate basally, glabrous or appressed hairy elsewhere, hairs to 5 mm, margins hyaline; ligules 0.2-0.6 mm; blades 20-50 cm long, 1.2-2(3) mm wide, flat, folded or involute, dark green, remaining so well into winter, glabrous on both surfaces or the adaxial surface sparsely hairy basally, margins scabridulous. Panicles 15-30 cm long, 2-6 cm wide, open (contracted when immature), longer than wide, pyramidal to ovate, not diffuse; lower nodes with 1-2(3) branches; primary branches 2-8 cm, appressed or spreading to 50° from the rachis, not capillary, without spikelets on the lower 1/3; secondary branches spreading; pulvini hairy or glabrous; pedicels 2-22 mm, longer than the spikelets, spreading, glabrous, scabridulous. Spikelets 3.5-6.5 mm, purplish-brown. Glumes linear-lanceolate, membranous; lower glumes 2.4-4.5 mm, 0.6-0.83 times as long as the upper glumes; upper glumes (3.5)4-6(6.5) mm, as long as or longer than the florets; lemmas 3.4-4.3 mm, ovate to lanceolate, membranous, glabrous, acute; paleas 3.4-4.4 mm, ovate, membranous, glabrous; anthers 2.5-3.4 mm, purplish. Fruits 1.8-2.2 mm, fusiform, brown. 2n = unknown.

Sporobolus pinetorum grows in wet to moist pine woodlands, in soils seasonally to semi-permanently saturated, at elevations of 0-160 m. It is endemic to the southeastern United States.