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

568 CYPERACEAE/CYPERUS
was from Mexico in 1851, with the first known U.S. reports from the 1930s. Tyndall (1983) concluded
that the species is transported at least partially by birds (presumably achenes on feet,
etc.). According to Tucker (1987), this weedy species is able to complete its life cycle in as little as
one month, with a single plant producing thousands of achenes. It is considered by some
sources to be among the world’s worst weeds (Holm et al. 1977). � I
Cyperus digitatus Roxb., (fingered, with fingers), FINGER FLAT SEDGE. Plant coarse perennial
similar to C. erythrorhizos; culms to 150 cm tall, (2–)4–15 mm wide; inflorescences with spikelets
in relatively crowded cylindrical spikes; achenes ca. 0.9 mm long. Moist areas, ditches, pond
margins; Limestone, Robertson, Van Zandt (BRIT), and Trinity (Turner et al. 2003) cos.; mainly
Gulf Prairies and Marshes and South TX Plains; FL and TX. Jun–Nov.
Cyperus drummondii Torr. & Hook., (for its collector, Thomas Drummond, 1780–1835, Scottish
botanist and collector in North America), DRUMMOND’S FLAT SEDGE. Tufted perennial; culms 35–
170 cm tall, sharply 3-angled, scabrous on angles only; leaf blades, leaf sheaths, and bracts with
knot-like septa visible under a hand lens; spikelets in digitate head-like clusters; achenes 1–1.2
mm long. Pond margins, seeps, coastal prairies, typically in less disturbed areas than the related
C. virens (Carter et al. 1999); Harris (Rosen 2004) and Orange (Carter et al. 1999) cos. near se
margin of East TX; also Fort Bend Co. (BRIT) in the Gulf Prairies and Marshes and Goliad Co.
(Carter et al. 1999) in the South TX Plains; e U.S. from SC s to FL w to TX. May–Oct. [C. robustus
Kunth, C. virens var. drummondii (Torr. & Hook.) Kük., C. virens subsp. drummondii (Torr. &
Hook.) T. Koyama, C. virens var. robustus (Kunth) Kük.] While some authorities (e.g., Kartesz
1999) combine this taxon with C. virens, we are following Carter et al. (1999) and Tucker et al.
(2002) in recognizing it as a separate species. Carter et al. (1999) gave an extensive analysis and
justification. While not officially designated as such (e.g., TOES 1993; Carr 2002d; Poole et al.
2002), given its limited distribution in the state, we consider this species to be of conservation
concern in TX. �
Cyperus echinatus (L.) A.W. Wood, (prickly), GLOBE FLAT SEDGE, CYLINDER FLAT SEDGE. Tufted
perennial; culms 15–70(–100) cm tall, corm-like at base; heads or spikes globose or subglobose,
8–21 mm long, 8.5–18 mm broad, less than 1/4 longer than broad, the spikelets arranged so
densely that outline of spike is ± smooth; achenes (1.5–)1.8–2.3 mm long. Sandy open areas, often
in disturbed places; Pineywoods and n Gulf Prairies and Marshes w to West Cross Timbers and
e edge of Edwards Plateau; widespread in the e 1/2 of the U.S. May–Oct. [C. ovularis (Michx.)
Torr.] m/284
Cyperus elegans L., (elegant), STICKY FLAT SEDGE, ROYAL FLAT SEDGE. Tufted viscid (= sticky) perennial
25–80 cm tall; leaf blades involute, nodulose (= with knot-like septa visible with a hand
lens) basally when dried; inflorescences with longer rays branched into head-bearing secondary
rays, the spikelets mostly in digitate head-like clusters; achenes 1.5–2 mm long. Damp
soils, ditches, open areas; Hardin, Newton (BRIT), Bexar, Freestone, Harris, Orange, and Travis
(Turner et al. 2003) cos.; scattered mainly s 1/2 of TX; FL, LA, NM, and TX. Jul–Nov.
Cyperus entrerianus Boeck., (from Entre Rios, the name of an historically disputed area now in
Argentina and the type locality of the species—Carter 1990), WOODRUSH FLAT SEDGE. Perennial
usually 65 cm or less tall; spikelets in digitate head-like clusters; achenes ca. 1 mm long. Ditches,
other moist areas; Harris, Montgomery (BRIT), Jefferson, Newton, and Waller (Turner et al.
2003) cos.; also Gulf Prairies and Marshes; se U.S. from GA s to FL w to TX. Jul–Sep. [Cyperus
luzulae of authors, not (L.) Rottb. ex Retz., C. luzulae var. entrerianus (Boeck.) Barros] Native of
Latin America. This introduced species can be locally abundant and “seems highly correlated
with rice culture” (Carter 1990). According to Tucker et al. (2002), it was first collected in the
U.S. in FL in 1941. It has in the past been confused with C. luzulae, a species that does not occur
in North America (Tucker et al. 2002). I