Species very rarely found in our area are included, but unlinked, in this key

1. Bracts green or absent…3

1. Bracts white…2

2. Bracts 6 or fewer, < 5 mm wide at base…R. colorata

2. Bracts 6 or more, > 5 mm wide basally…R. latifolia

3. Spikelets, achenes, and tubercles < 10 mm long…5

3. Spikelets, achenes and tubercles > 10 mm long…4

4. Bristles 2X the achene length…R. inundata

4. Bristles ½ the achene length…R. corniculata

5. Spikelets arranged variously but not in globose heads…6

5. Spikelets in globose heads…R. tracyi

6. Spikelets clustered...10

6. Spikelets borne singly on individual pedicels (sometimes in small clusters)…7

7. Leaves extremely thin, ca. 0.3 mm wide; perianth bristles plumose but shorter than half the length of the achene body…R. galeana (Spikelets usually single or in small clusters. Bristles 6, not going past middle of achene, plumose. Achene with wrinkled surface, 1.5-2 mm long, approximately as wide as long)

7. Leaves > 0.3 mm wide; perianth bristles not plumose…8

8. Leaves 0.5-1 mm wide; bristles ½ achene length…R. rariflora (Small plants with the 3-4.5 mm spikelets mostly single or in tiny clusters. Looks like miniature R. inundata. Bristles with no plume, ½ the achene length, this 1.8-2 mm, strongly rugose. Could be confused with Fimbristylis autumnalis but the Fimbristylis with symmetrical cymose branching and longer spikelets [> 5 mm vs. < 4 mm])

8. Leaves > 1 mm wide; bristles either absent or exceeding achene…9

9. Leaves 1-5 mm wide; spikelets nearly black when mature, 4-6 mm long; achenes 1-1.3 mm long; bristles absent…R. nitens

9. Leaves 4-7(10) mm wide; spikelets 2.5-3.3 mm long, not black; achenes 1.3-1.5 mm long; bristles exceeding tubercle…R. miliacea (Looks like miniature Sawgrass; achenes rugose, tubercle 0.2-0.3(0.4) mm long)

10. Achene bristles absent, smooth, or with tiny barbs…14

10. Achene bristles plumose…11

11. Bristles shorter than half the length of the achene body...R. galeana (Usually with one spikelet or these very few, the spikelets to 6(8) mm long)

11. Bristles > than half the length of the achene body...12

12. Spikelets 8-10 mm long...R. megaplumosa (Bristles plumose, 5-7.5 mm long, much longer than achene (this > 2 mm long). The bristles pushing outward, MUCH longer than in R. plumosa or R. pineticola)

12. Spikelets 3.5-6 mm long...13

13. Achene body (1.5)2-2.2 mm long, the tubercle 0.5-0.8(1) mm long; bristles exceeding the achene; leaves (1)2-3 mm wide…R. pineticola (Synonym of R. intermedia in Wunderlin, and possible synonym of R. plumosa--see discussion under that species)

13. Achene body 1.3-1.8(2) mm long, the tubercle 0.3-0.5 mm long, the bristles usually not exceeding the tubercle; leaves 1-1.5 mm wide…R. plumosa

Note! In: Godfrey, R. K. & J. W. Wooten, Aquatic and Wetland Plants of Southeastern United States, Monocotyledons. P. 370. R. intermedia (R. pineticola) is treated as a synonym of R. plumosa with a brief discussion of the authors' inability to perceive two separate taxa. We experience the same difficulty.

14. Achene with bristles absent, smooth, or antrorsely barbed…16

14. Achene with bristles retrorsely barbed…15

15. Achene 2.5 mm long…R. microcephala

15. Achene 3 mm long…R. cephalantha

16. Bristles < 9 in number or absent…17

16. Bristles > 9 in number…R. baldwinii

17. Perianth (bristles) present…19

17. Perianth (bristles) absent…18 (also true of R. globularis)

18. Achene 1-1.8 mm long…R. chapmanii (Bracts rising up sharply on both sides of the spikelet cluster, forming a V)

18. Achene 0.8 mm long…R. divergens (Small grassy species. This the only one of our species with the achene < 1 mm long)

19. Leaf blades with long tapering tips (or too narrow to tell)…20

19. Leaf blades abruptly acute…R. ciliaris (Central nerve of scales pubescent)

20. Spikelets ovate or lanceolate…21

20. Spikelets nearly globose…R. globularis (Spikelets (2)2.5-3(4) mm long; globular-semi-globose. Achene 1.5-1.8 mm long, rugose, the perianth shorter than the body)

21. Achene less than twice as long as wide…22

21. Achene twice as long as wide...R. curtissii (Rare in our area if present at all. Cespitose. Leaves 1 mm wide, involute. Spikelets in tight heads, ascending at 45 degrees, these mostly terminal. Achenes 2X as long as broad, 1.2-1.5 mm long, finely reticulate)

22. Achene patterned on the surface: rugose or reticulate…28

22. Achene smooth, the bristles antrorsely barbed…23

23. Achene > 3 mm long; leaves > 3 mm wide; scrub habitats…R. megalocarpa

23. Achene < 3 mm long; leaves < 3 mm wide; habitat is not scrub…24

24. Achene 1-1.2 mm long…R. fernaldii (Leaves to 1(1.5) mm wide; spikelets 2-2.5 mm long. Bristles shorter than tubercle tip (vs. longer than the tip in similar R. filifolia), the tubercle 0.2-0.3 mm long)

24. Achene > 1.2 mm long…25

25. Achene 1.5 mm long; bristles longer than tubercle…R. filifolia (Leaf blades 1-2 mm wide. Spikelets 2.5-3(3) mm long. Tubercle 0.4-0.6 mm long)

25. Achene > 1.5 mm long; bristles shorter than tubercles…26

26. Leaves > 1.5 mm wide…R. fascicularis (Spikelets (3)3.5-6 mm long; achene about 2 mm long)

26. Leaves < 1 mm wide…27

27. Spikelets 5-7 mm long…R. harperi (Plants of Hypericum marshes. Spindly, with the spikelets sessile in terminal and lateral clusters. Leaves 0.5-1 mm wide. Scales with short awn. Fruit 2.1-2.5 mm long, glossy. Tubercle large: 0.9-1 mm long)

27. Spikelets < 3.5 mm long… R. wrightiana (Spindly, the leaves < 1 mm wide. Spikelet 2.5-3.5(4) mm long. Achene (1.8)2-2.5 mm long. Tubercle 1.5-1.7 mm long, often abruptly narrowed with concave sides or triangular.

28. Spikelets 5-6 mm long…R. odorata (Leaf blades 3-6 mm wide; achene 3 mm long)

28. Spikelets < 5 mm long…29

29. Plants resembling miniature Sawgrass; leaves 4-7(10) mm wide…R. miliacea (Spikelets 2.5-3.5 mm long, in clusters along the stem, on thin droopy branches, each spikelet terminating its own pedicel. Achenes 1.3-1.5 mm long, rugose; tubercle 0.2-0.3(0.4) mm long)

29. Leaves < 4 mm wide…30

30. Achene < 1 mm long; bristles absent…R. divergens (Spikelet 2-2.5 mm long)

30. Achene > 1 mm long; bristles present…31

31. Leaf blades usually < 2 mm wide; achene < 1.5 mm long; spikelets in lax clusters…R. microcarpa

31. Leaf blades > 2 mm wide; achene > 1.5 mm long; spikelets in dense clusters…32

32. Achene 1.5-1.6(1.8) mm long…R. decurrens (Leaf blades 2-4 mm wide. Spikelets 2.5-3.5 mm long)

32. Achene 2.5-3 mm long…R. grayi (Leaf blades 2-4 mm wide, grayish; achene 2.5-3 mm long, the body 2 mm long, with a slightly thickened collar around the base of the tubercle)