The Sedge Family
Schoenoplectus/Schoenoplectiella
1 Main involucral bracts 2-8, spreading and leafy (inflorescence thus appearing terminal); rhizomes bearing ovoid tubers; bristlespersistent on achene; achenes 2.5-5mm long ....................................................................................................................... [see Bolboschoenus]
1 Main involucral bract 1 (rarely with additional 1-2 lateral bracts), erect and rounded or triangular, appearing as a continuation of stem
(inflorescence thus appearing lateral, though in some species longer inflorescence branches may overtop bract); rhizomes not bearing
tubers; bristles falling from achene; achenes 1.0-4.5mm long.
2 Spikelets on stalks of varying lengths, at least some clearly not sessile .............................................................. Soft-stemmed Bulrush
2 Spikelets all sessile, in a cluster at one point (rarely with 1 or 2 short branches to 5mm long).
3 Spikelet solitary; leaves numerous; plant usually aquatic, stems and leaves flaccid, supported by water ..................... Water Bulrush
3 Spikelets (1-)2-several; leaves 1-4; usually of wet places, but stems stiff and erect, not floating.
4 Clump-forming annual or perennial; stems rounded, 10-60cm tall ........................................................................... Smith's Bulrush
4 Rhizomatous perennial; stems triangular in cross-section, usually 50-200cm tall.
5 Sides of stem strongly concave, wing-angled; stems 3-10mm in diameter; main involucral bract 1-2.5(-6)cm long; spikelet scale
with apical notch 0.1-0.4mm deep ............................................................................................................................. Olney's Bulrush
5 Sides of stem flat, slightly concave, or slightly convex; stems 1-6mm in diameter; main involucral bract (1-)3-20cm long; spikelet
scale with apical notch (0.3-) 0.5-1mm deep ........................................................................................................ American Bulrush
Eleocharis
1 Spike 1-2(-2.5)× as thick as stem immediately below spike, gradually expanded from stem, base of spike narrowly cuneate; spike(3-)4-8× as long as wide ....................................................................................................................................................................... Key A
1 Spike more than twice as thick as stem immediately below spike, abruptly expanded from stem, base of spike broadly cuneate, rounded,
or truncate; spike 1-3(-4)× as long as wide.
2 Seeds with several distinct longitudinal ribs or low ridges, intervening spaces with abundant, very narrow, horizontally elongate
cells .................................................................................................................................................................................................... Key B
2 Seeds without longitudinal ribs, surface smooth, granular, or honeycomb-like.
3 Seeds lenticular or biconvex; styles 2-branched ............................................................................................................................ Key C
3 Seeds three-sided or nearly round; styles 3-branched .................................................................................................................. Key D
1 Stem transversely partitioned (appearing jointed), about 5-9.5mm in diameter .............................................................Jointed Spikerush
1 Stem not appearing jointed, 1-5.5mm in diameter.
2 Spike 3-5mm in diameter, to 5cm long, rounded to obtuse at tip, densely flowered, flowers (scales) 50-100 per spike, arranged in obvious
spiral rows; culm 2-5mm in diameter; [estuarine and riverine marshes, or brackish dune swales on barrier islands] .................................
.........................................................................................................................................................................Square-stemmed Spikerush
2 Spike 1-2mm in diamater, to 2.5cm long, sharply pointed at tip, loosely flowered, flowers (scales) 10-25, few enough that spiral
arrangement is not readily apparent; culm 0.5-1.5(-2)mm in diameter; [limesink (doline) ponds and lakes of mainland] ..........................
.........................................................................................................................................................................................Robbins' Spikerush
1 Stems about 0.5mm thick, firm, not wrinkling in drying; spikes 3-6mm long; [widespread] .......................................... Needle Spikerush
1 Apex of sheath thin, membranous, hyaline, often with a torn edge.
2 Seeds rufous-brown to reddish-purple to black, (0.3-)0.4-0.6mm wide; longer bristles retrorsely barbed, shorter than to equaling seed
body ...................................................................................................................................................................................... Pale Spikerush
2 Seeds olivaceous-brown to black, 0.5-0.7(-0.8)mm wide; longer bristles either retrorsely barbed and equaling to exceeding tubercle, or
smooth and shorter than tubercle.
3 Bristles retrorsely barbed, the longer equaling to exceeding tubercle; [wet sandy or peaty habitats, widespread] .....Olive Spikerush
3 Bristles smooth, the longer shorter than tubercle; [tidal rivers] .....................................................Olive Spikerush var. reductiseta
1 Apex of sheath firm, somewhat thickened, opaque, with a definite edge.
4 Rhizomatous perennials growing from thick horizontal rhizomes.
5 Basal (sterile) scales 2-3, lowest not encircling base of spike ............................................................................Common Spikerush
5 Basal (sterile) scale solitary and spathiform, encircling base of spike.
6 Seeds prominently reticulate-pitted ............................................................................................................... Creeping Spikerush
6 Seeds smooth to faintly reticulate.
7 Stemslender to filiform; scales obtuse, 30-40 per spike ....................................................................................... Bald Spikerush
7 Stems thicker, somewhat inflated; scales acute, 5-30 per spike ................................................................ Saltmarsh Spikerush
4 Tufted or cespitose annuals without thick horizontal rhizomes.
8 Tubercle flat-deltoid, 1/4 as high as seed; bristles shorter than seed body; [clay soils only] ............Engelmann's Spikerush
8 Tubercle short-conic, 1/3-1/2 as high as seed; bristles much exceeding tubercle; [variety of soils] ................Blunt Spikerush
1 Seeds roughly and coarsely honeycomb-reticulate; plants usually forming dense, broad tussocks.
2 Tubercle much narrower than seed; stems lax, often reclining, distinctly 3-angled, twisted .................................... Twisted Spikerush
2 Tubercle as broad or broader than seed; stems ascending to erect, subterete, not twisted ....................... Large-tubercled Spikerush
1 Seeds smooth to finely honeycomb-reticulate.
3 Tubercle confluent with seed summit, not constricted at base.
4 Seeds bicolored, body black, tubercle whitish, depressed; [freshwater ponds]............................................... Black-fruited Spikerush
4 Seeds unicolored, body and tubercle light brown or olive brown; [brackish to saline marshes].
5 Plants diminutive, stems slender, rounded, 1-7cm long, not arching and rooting ..................................................... Dwarf Spikerush
5 Plants robust, stems broad, flattened, 20-80cm (or more) long, at least some arching and rooting at tips ............ Beaked Spikerush
3 Tubercle not confluent with seed summit, constricted at base.
6 Seeds with prominent keel-like angles or ribs .................................................................................................. Three-ribbed Spikerush
6 Seeds with rounded angles.
7 Seeds white or very pale gray.
8 Tubercle depressed-deltoid; scales rounded, appressed .................................................................................... Britton's Spikerush
8 Tubercle conic or deltoid; scales acute to attenuate, the tips free ............................................................. Small-fruited Spikerush
7 Seeds yellowish, brown, or olive.
9 Seeds not honeycomb-reticulate ............................................................................................................... Flat-stemmed Spikerush
9 Seeds honeycomb-reticulate.
10 Seeds 1.2-1.7mm long, at maturity normally with bristles ............................................................................Creeping Spikerush
10 Seeds 0.7-1.2mm long, with or without bristles .............................................................................................. Slender Spikerush
Rhynchospora
Identification notes: Measurements and descriptions of seed are of seed body only, not including tubercle, unless otherwise indicated.
1 Tubercles 3-23mm long; style simple or bifid only at tip ..................................................................................................................... Key A1 Tubercles less than 3mm long; style divided into 2 slender stigmatic branches.
2 Bristles present, retrorsely barbed (at least distally), or antrorsely barbed and straplike (flattened) ............................................ Key B
2 Bristles absent, or present and smooth, or antrorsely barbed and filiform.
3 seed surface smooth, minutely pitted, or finely striate (not ridged, rugose, or reticulate) ............................................................ Key C
3 Seed surface transversely ridged, rugose, or honeycombed-reticulate (sometimes faintly so) ..................................................... Key D
................................................................................................................................................................................ Tall Horned Beak-sedge
1 Plants rhizomatous; primary clusters with 1-6 loosely clustered spikelets; seed (3.5-)4.0-4.8mm long ....................Horned Beak-sedge
1 Bristles 6 or fewer, either retrorsely or (rarely) antrorsely barbed their entire length; spikelets variously brown, rufous, or tan
(or very rarely white).
2 Spikelets 1-fruited, the solitary seed terminating the axis; clusters 1-7, globose to turbinate.
3 Clusters globose to turbinate; seed (from base of bristles) 1.3-1.8mm long, 0.65-0.95mm wide; tubercle 0.7-1.6mm long.
4 Clusters turbinate to hemispheric (rarely subglobose), lowest spikelets usually spreading-ascending to spreading; larger leaves
< 2mm wide; seed 1.6-1.8mm long; tubercle 1.0-1.6mm long .....................................................................Loose-headed Beak-sedge
4 Clusters globose to subhemispheric, lowest spikelets usually reflexed; larger leaves > 2mm wide; seed 1.3-1.6mm long;
tubercle 0.7-1.2mm long .............................................................................................................................. Small-headed Beak-sedge
3 Clusters globose to hemispherical; seed (from base of bristles) 1.8-2.6mm long, 1.1-1.8mm wide; tubercle 1.4-2.4mm long ................
................................................................................................................................................................................ Bunched Beak-sedge
2 Spikelets 1-5 fruited (if 1-fruited, then axis terminated by sterile floret); clusters 2-many, ovoid to turbinate (rarely globose).
5 Clusters numerous, usually 20 or more; tubercle 1.3-1.8mm long; seed 1.1-1.4mm wide, 1.5-2.0mm long, summit narrowly truncate,
faces knobly, margin thickened and wire-like; leaves 2.5-7mm wide .................................................................. Clustered Beak-sedge
5 Clusters 2-8; tubercle 0.4-1.2mm long; seed 0.6-1.2mm wide, 1.1-2.0mm long, summit more rounded than truncate, faces lenticular,
wire-like margin narrow or not evident; leaves 0.2-3.5mm wide.
6 Seed 0.6-0.8mm wide, 1.1-1.3mm long; tubercle 0.4-0.6mm long; bristles more-or-less equaling seed .....Knieskern's Beak-sedge
6 Seed 0.8-1.2mm wide, 1.3-2.0mm long; tubercle 0.8-1.6mm long; bristles more-or-less equaling tubercle ....Brownish Beak-sedge
1 Bristles present (if rudimentary, then 4-6); scales tan, rufous, or brown.
2 Seed 0.6-1.1mm wide, pyriform, obovoid, or narrowly elliptic, pale to dark brown but not blackish; tubercle margin setose.
3 Leaves to 1.5(-2)mm wide; seed 1.0-1.7mm long, 0.9-1.1mm wide; tubercle 0.5-1.5mm long .................................Brown Beak-sedge
3 Leaves filiform, < 1mm wide; seed 0.8-1.3mm long, 0.6-0.9mm wide; tubercle 0.4-0.8mm long ............Thread-leaved Beak-sedge
2 Seed > 1mm wide, suborbicular or broadly ellipsoid; tubercle margin smooth or roughened but not setose ..........Slender Beak-sedge
1 Stems stouter; leaves wider, not filiform.
2 Seed faces flat or concave; when one face concave, opposite face sometimes slightly convex .............................. Torrey's Beak-sedge
2 Seed biconvex or appearing swollen.
3 Bristles present ..............................................................................................................................................................Globe Beak-sedge
3 Bristles absent; seed 0.7-1.0mm long.
4 Scales broadly ovate, obtuse to sub-acute; seed strongly transversely ridged; tubercle depressed, broader than long; style not
persistent ....................................................................................................................................................... Short-beaked Beak-sedge
4 Scales lance-ovate, acute; seed weakly transversely ridged; tubercle triangular-lanceolate, as long as broad or longer; style usually
persistent.........................................................................................................................................................Long-beaked Beak-sedge
Scleria
Identification notes: Scleria superficially resembles Rhynchospora in the field, but mature specimens are readily recognized by the terete white, gray, or black bony seeds. Hardened seeds are necessary for reliable identification to species. In the key, seed length includes hypogynium (a circular, angular, lobed, or tuberculate disk differing in texture and structure from seed body) when present. The scale character applies only to ultimate bracteate structure clasping seed.
1 Base of seed without hypogynium, seed base constricted, pitted and/or ribbed, but appearing as a continuation of seed body ........................................................................................................................................................................................................................ Low Nut-rush
1 Base of seed with hypogynium.
2 Seed body smooth (often longitudinally ribbed); hypogynium with 0, 8, or 9 tubercles.
3 Seed 1-2mm long; stem 1-2mm wide at base; leaves 1-3mm wide................................................................................. Slender Nut-rush
3 Seed 2-4mm long; stem 2.5-6mm wide at base; leaves 5-9mm wide.
4 Sheaths brown or straminous to reddish, glabrous to glabrate on ventral surface except for a pubescent and usually thickened summit;
inflorescences terminal and lateral; seeds 2.0-3.3mm long, (1.12-) avg. 1.25 (-1.38)× as long as wide; hypogynium surface with laterally
and apically rounded papillae; [pinelands] ....................................................................................................................... Whip Nut-rush
4 Sheaths purple to reddish, ventral surface uniformly pubescent; inflorescences terminal only or terminal and lateral; seeds 2.5-4.0mm
long, (1.35-) avg. 1.45(-1.54)× as long as wide; hypogynium surface with rounded or flattened papillae ...................Shining Nut-rush
2 Seed reticulate or papillose, rarely smooth; hypogynium with 3 tongue-shaped lobes, or 3 or 6 tubercles.
5 Hypogynium with 3 or 6 tubercles; seed papillose, sometimes reticulate (if so, pits generally variable in shape, not forming regular
rows), or rarely smooth ..................................................................................................................................... Few-flowered Nut-rush
5 Hypogynium of 3 tongue-shaped lobes appressed to underside of seed (appearing nearly bract-like); seed reticulate, pits generally
squarish or rectangular, arranged regularly in rows, rarely smooth.
6 Seed pubescent (occasionally becoming glabrate); lower lateral inflorescences on long, filiform, usually drooping peduncles; bract
of uppermost lateral inflorescence usually reaching from 1/3-3/4 length of terminal internode; terminal internode 6-30cm long ......
....................................................................................................................................................................................... Pitted Nut-rush
6 Seed glabrous; lower lateral inflorescences sessile or on short-erect peduncles; bract of uppermost lateral panicle usually reaching
3/4 length of to exceeding terminal internode; terminal internode 3-8 cm long .....................................................Netted Nut-rush