keys to the vascular plants of east texas - Botanical Research ...

570 CYPERACEAE/CYPERUS
Cyperus erythrorhizos Muhl., (red-rooted), RED-ROOT FLAT SEDGE. Tufted annual 5–60(–120) cm
tall, quite variable in size; fresh roots usually reddish; culms usually 1–3 mm wide; inflorescences
umbel-like clusters of spikes; rays unequal; spikes several per peduncle, cylindrical, relatively
crowded; scales relatively small, 1.3–1.5 mm long; achenes 0.7–1 mm long. Marshy areas,
lake margins; widespread in the e 1/2 of TX; also El Paso Co. (Turner et al. 2003) in the Trans-
Pecos; s Canada and widespread in much of the U.S. Jul–Dec. m/284
Cyperus esculentus L., (edible), YELLOW NUT-GRASS, CHUFA, NORTHERN NUT-GRASS, CHUFA FLAT
SEDGE. Perennial, colonial, usually 15–60 cm tall; rhizomes often with tuber-like thickenings; inflorescences
with spikes loose, the spikelets spread apart so that the inflorescence axis is usually
visible at a glance; anther connective prolonged into a red dot 0.05–0.1 mm long; achenes
(1.1–)1.3–1.5(–1.6) mm long. Disturbed soils, ditches, swales, cultivated fields, near streams, moist
areas; scattered nearly throughout TX; s Canada and throughout the U.S. Summer–fall. According
to Mabberley (1987), this species is native to w Asia and Africa and widely naturalized in
the New World; however, Tucker (1994) and Tucker et al. (2002) regard the species to be cosmopolitan—they
divide it into varieties and consider var. esculentus to be restricted to the Old
World, with several varieties native to North America. [C. esculentus var. angustispicatus Britton,
C. esculentus var. leptostachyus Boeck., C. esculentus var. lutescens (Torr. & Hook.) Kük., C.
esculentus var. macrostachyus Boeck.] Schippers et al. (1995) discussed infraspecific variation in
this widespread species. It is a state noxious weed in AZ, CA, CO, NC, NV, OR, and WA (Kartesz
1999), can be a troublesome weed infesting a variety of crops, and is considered by some sources
to be among the world’s worst weeds (Holm et al. 1977). It is now known as a weed in all 50 U.S.
states and s Canada (Tucker 1987). The nut-like, edible, tuber-like thickenings were an important
food in ancient Egypt (Pascual et al. 2000) and were used during pioneer days in this country
(Crosswhite 1980); the species is currently being studied for additional uses (Pascual et al.
2000). While varieties are sometimes recognized in this species (e.g., Schippers et al. 1995; Jones
et al. 1997; Kartesz 1999; Tucker et al. 2002), we have been unable to consistently distinguish the
taxa and are following Yatskievych (1999) in not recognizing infraspecific taxa. For those wishing
to distinguish varieties, the following key (from Tucker et al. 2002) separating the two attributed
to East TX may be helpful. This species is somewhat similar to C. rotundus (also with
tuber-like thickenings on the rhizomes); see discussion under that species. �
1. Spikelets (1.2–)1.5–2 mm wide; floral scales 1.8–2.7 mm; anthers (1–)1.3(–1.6) mm; styles (0.7–)1–
1.2 mm; stigmas (1.2–)1.8(–2.5) mm ______________________________________________ var. leptostachyus
1. Spikelets 2.4–3 mm wide; floral scales (2.7–)2.9–3.4(–3.6); anthers (1.2–)1.3–2(–2.1) mm; styles
(0.9–)1.3–2(–2.2) mm; stigmas (2–)2.3–2.8 (–4) mm _________________________________ var. macrostachyus
Cyperus filiculmis Vahl, (with thread-like culms), FERN FLAT SEDGE. Tufted perennial 15–40(–
48) cm tall; inflorescences with spikelets in digitate head-like clusters; achenes 1.8–2.2 mm
long. Open areas, often in well-drained soils; Waller (BRIT), Brazos, Freestone, and Robertson
(Turner et al. 2003) cos. in s part of East TX; also Comal Co. (TAMU) at w margin of East TX;
also Cross Timbers and Prairies and Edwards Plateau; se U.S. from MD s to FL w to TX. Jun–
Sep(–Oct). [C. martindalei Britton] This species has often in the past been treated more broadly
to include C. lupulinus (e.g., apparently by Correll & Johnston 1970 and Hatch et al. 1990),
which is here recognized as a distinct species.
Cyperus flavescens L., (yellowish), YELLOW FLAT SEDGE. Tufted annual usually 10–30 cm tall; scales
of spikelets yellow-green to yellowish brown; inflorescences with spikelets in ± head-like clusters;
achenes lenticular, usually black, shiny, 1–1.2 mm long, with rectangular to linear (vertical) cells,
the rows of cells marked by horizontal, wavy, usually discolored sutures (transverse undulations).
Moist sand, often disturbed areas; scattered in East TX; also Gulf Prairies and Marshes, Cross Timbers
and Prairies, and Edwards Plateau; se Canada and widespread in e 1/2 of the U.S, also CA.
Jul–Nov. [C. flavescens var. poiformis (Pursh) Fernald, Pycreus flavescens (L.) Rchb.]