Rhynchospora knieskernii
Rhynchospora plumosa
knieskern's beaksedge
plumed beaksedge
erect to arching, leafy, linear to filiform, nearly triangular.
erect or excurved, filiform to linear.
ascending, overtopped by culm;
blades flat, linear to filiform, to 1.8 mm wide, apex distally involute, trigonous, setaceous.
erect or excurved, shorter than scape;
blades filiform to linear, to 1.5 mm wide, margins involute, apex trigonous, tapering.
terminal and axillary, spikelet clusters 2–4, widely spaced, the lowest near plant base;
clusters compact, broadly turbinate to hemispheric, to 1.5 cm wide; leafy bracts curved, setaceous, slightly to greatly overtopping subtended compounds.
spikelet clusters 1–several, dense or sparse, when several, either widely spaced or close together, if widely spaced then ovoid to hemispheric, if close together then lobed ellipse or cylinder; leafy bracts filiform, setaceous, overtopping each cluster.
dark brown, lance-ellipsoid, 2–3 mm;
fertile scales 2 mm, apex acute, midrib short-excurrent or not.
light redbrown to deep brown, broadly fusiform to ovoid, (2.5–)3.5–4 mm, apex acute to acuminate;
fertile scale broadly ovate, strongly convex, (1.5–)2–3 mm, apex acuminate to mucronate, midrib excurrent or not.
perianth bristles 6, ± as long as fruit body, retrorsely barbellate.
perianth bristles 6, plumose, reaching at least to fruit midbody, often to tubercle tip.
mostly 2 per spikelet, 1.5–1.9 mm;
body brown with yellowish center, ellipsoid, lenticular distal to short stipe, 1–1.3 × 0.6–0.8 mm;
tubercle triangular, 0.3–0.6 mm, distinctly shorter than fruit body.
1(–2) per spikelet, (1.5–)2–2.5 mm;
body redbrown or brown, tumidly obovoid or ellipsoid, sometimes obscurely lenticular, (1.2–)1.3–1.8(–2) × 1–1.5 mm;
surfaces interruptedly crossrugulose;
tubercle narrowly to broadly conic, mostly 0.3–0.5 mm, base flaring, round or indistinctly 2lobed.
Rhynchospora knieskernii
Rhynchospora plumosa
Of conservation concern.
Rhynchospora knieskernii is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Particularly in Gulf Coastal Plain savannas, Rhynchospora plumosa appears to have two distinct morphs: one very densely cespitose with filiform leaves, filiform, arching culms, and spikelets in short, broad, dark brown clusters, and the other morph taller, stiffer, with broader leaves and culms, and longer, sharper, paler spikelets in narrow compounds of clusters. After many attempts to do what others have—namely to create two distinct species—I have had to retrench, because so many intergrades occur.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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