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

594 CYPERACEAE/ELEOCHARIS
the U.S. Summer. This species is part of the very difficult “E. palustris complex,” which in TX is
reported to include E. erythropoda, E. macrostachya, and E. palustris (Smith 2002d)—see E.
macrostachya and E. palustris for further discussion. Due to uncertainty regarding species limits,
all TX members of the E. palustris complex are mapped together as E. palustris; no separate
county distribution map is provided for E. erythropoda. [E. calva Torr.—an invalid name, Scirpus
glaucus Torr.] This species is apparently avoided by cattle, hence the common names (Catling
1994). Hybrids with E. compressa have been reported from Canada (Catling 1994).
Eleocharis flavescens (Poir.) Urb., (yellowish), PALE SPIKE-RUSH, YELLOW SPIKE-RUSH, WRINKLE-
SHEATH SPIKE-RUSH. Perennial with elongate rhizomes 0.5–1 mm thick, delicately mat forming;
culms 4–42 cm tall; distal leaf sheath with apex loose, thin-membranous and transparent, often
conspicuously wrinkled, frequently disintegrating; spikelets (1.5–)3–7(–9) mm long, ellipsoid,
with up to 65 scales; achenes biconvex, (0.4–)0.6–1.1 mm long; tubercle small, 0.2–0.7 mm
long. Throughout the growing season. This species is similar to and can be confused with the
annual E. geniculata (which has the apex of the leaf sheaths firm and opaque) (Godfrey &
Wooten 1979). Menapace (2002) noted that the varieties “are difficult to delimit, especially in
the south, and identifications of some specimens to variety are problematic.”
1. Achenes reddish just prior to maturity, dark brown to dark purplish black to nearly black at maturity,
only rarely highly constricted just below tubercle; perianth bristles usually as long as achenes
or shorter, sometimes vestigial ___________________________________________________ var. flavescens
1. Achenes green to almost brown, often highly constricted just below tubercle; perianth bristles
usually longer than achenes (often to twice as long) ____________________________________ var. olivacea
var. flavescens, PALE SPIKE-RUSH. Culms to 42 cm tall; scales of spikelets brown to yellow-brown.
Wet areas, sometimes in brackish conditions; sparsely distributed in e 1/2 of TX; se U.S. from
VA s to FL w to AR and TX, also scattered in w 1/3 of the U.S. Jun–Oct. [E. flaccida (Rchb.) Urb.]
var. olivacea (Torr.) Gleason, (olive-colored, greenish or greenish-brown), GREEN SPIKE-RUSH,
BRIGHT GREEN SPIKE-RUSH. Culms to 28 cm tall; scales of spikelets brown streaked with green.
Margins of lakes and ponds, marshes, bogs, and other wet areas; Anderson, Cherokee, Houston
(BRIT), Bastrop, Gonzales, Leon, and Milam (Turner et al. 2003 as E. olivacea) cos.; also extreme s
TX; se Canada and widespread in the e 1/2 of the U.S. Jul–Oct. [E. olivacea Torr., E. olivacea var.
reductiseta (Schuyler & Ferren) Schuyler & Ferren] This variety has often been treated as a
separate species (e.g., Godfrey & Wooten 1979; Hatch et al. 1990; Kartesz 1999; Turner et al.
2003). However, due to the morphological similarities, we are following Menapace (2002) in
treating it as a variety of E. flavescens.
Eleocharis geniculata (L.) Roem. & Schult., (jointed, bent like the knee), CAPITATE SPIKE-RUSH,
BENT SPIKE-RUSH. Tufted annual 4–45 cm tall; distal leaf sheath apex angled on one side to a
sharp point; spikelets (1–)3–6(–9) mm long, ovoid to broadly ovoid or nearly orbicular, usually
with 28–50(–many) scales; achenes biconvex, 0.5–1.1 mm long, black or purplish black; tubercle
small, 0.2–0.4 mm long. Moist calcareous soils, seeps, shores; mainly on w and s margins of East
TX, also Angelina and Brazos (Turner et al. 2003) cos.; widespread in TX except Plains Country;
se Canada and scattered in the U.S. except the nw. Throughout the growing season. [E. caribaea
(Rottb.) S.F. Blake, Scirpus geniculatus L.] The name E. caribaea has often been used for this
species (e.g., Hatch et al. 1990), but according to Menapace (2002), that name “is considered by
most contemporary authorities to be misapplied.” m/285
Eleocharis interstincta (Vahl) Roem. & Schult., (with a space between, interval), KNOTTED SPIKE-
RUSH. Coarse rhizomatous perennial; culms hollow, completely and regularly transversely septate,
40–100 cm tall, sometimes nodulose (knobby) toward sheath, but not just below spikelet;
distal leaf sheath apex angled on one side to a point; spikelets 22–45(–60) mm long, with numerous
scales; achenes biconvex, 1.4–2.2 mm long, noticeably sculptured when viewed with a