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

912 POACEAE/DIGITARIA
9. Inflorescence branches appressed or ascending, the inflorescence contracted; spikelets
crowded, overlapping; lemma of sterile, lower floret with hairs usually 2–5 mm
long; terminal pedicels of branches 1.7–6(–7) mm long; caryopsis (= fruit) abruptly
pointed ______________________________________________________________ D. californica
9. Inflorescence branches stiffly spreading, the inflorescence open; spikelets widelyspaced,
many of them not overlapping or only slightly so; lemma of sterile, lower
floret usually with hairs ca. 2 mm or less long; terminal pedicels of branches 7.4–20
mm long; caryopsis tapering gradually to a point ________________________________ D. patens
7. Spikelets not silky-pubescent, the inflorescences not appearing pubescent at arm’s length;
spikelets 1.5–2.8 mm long.
10. Plants perennial, the culms sometimes � stoloniferous and rooting at the lower nodes;
spikelets 2–2.6 mm long AND inflorescence branches 6–10(–13) cm long _____________ D. texana
10. Plants annual, the culms neither stoloniferous nor rooting at the nodes; spikelets
EITHER shorter than 2 mm OR inflorescence branches longer than 13 cm ____________ D. filiformis
Digitaria bicornis (Lam.) Roem. & Schult., (two-horned), ASIAN CRAB GRASS. Annual similar to
D. ciliaris, but yellow-green (Webster 1987); inflorescence branches digitately arranged or a few
solitary below; culms decumbent and often rooting at the nodes; leaf blades mostly glabrous
but with papilla-based hairs near ligule; spikelets (2.6–)2.8–3.6(–3.7) mm long; lemma of lower
floret of nearly sessile spikelet often glabrous or nearly so (except often villous marginally);
lemma of lower floret of pedicelled spikelet usually hairy; 2n = 72 (Gould 1975b). Sandy or
sandy loam soils; Bexar (BRIT), Austin, Grimes, Harris (SBSC), Angelina, Caldwell, Cass, Houston,
Lee, Leon, Robertson, and Walker (Turner et al. 2003) cos.; Webster (1980) mapped the species
as occurring widely in the Pineywoods and Post Oak Savannah of TX; also Gulf Prairies
and Marshes and South TX Plains; se U.S. from VA s to FL w to TX, also CA. Jun–Nov. [D.
diversiflora Swallen, Paspalum bicorne Lam.] There has been disagreement as to whether this
species is native to the U.S. or not (e.g., the common name). Some authorities indicate it was introduced
(e.g., Hatch et al. 1990). However, we are following recent sources who consider it native
(e.g., Kartesz 1999; Wipff 2003f). According to Webster (1980), the species is “common and
abundant on the sandy coastal plain of the southeastern states” and further, the “range of the
species is now known to include … eastern Texas.” Wipff (2003f) considered it native from the se
U.S. through Mexico to n South America and the West Indies. Webster and Shaw (1982) noted
that D. milanjiana (Rendle) Stapf, MADAGASCAR CRAB GRASS, an introduced African perennial
similar to D. bicornis, is known from s TX. It can be distinguished from D. bicornis (and the
other similar annuals, D. ciliaris and D. sanguinalis) by its glabrous leaves (versus leaves with
hairs at least in the region of the ligule in the other annual species).
Digitaria californica (Benth.) Henrard, (of California—reflecting that the first collection was
made in Baja California—Wipff 2003f), CALIFORNIA COTTON-TOP, ARIZONA COTTON-TOP,
CALIFORNIA CRAB GRASS. Tufted perennial from a knotty base; culms erect, ca. 50–100 cm tall;
leaf blades glabrous or the upper surfaces villous; inflorescence usually silvery- or purpletinged
due to conspicuous pubescence, the branches digitately arranged or nearly so, usually
appressed, densely-flowered; spikelets 3–4(–5.4) mm long (excluding hairs); upper glume and
margins of lower lemma densely long-hairy, the hairs 2–5 mm long; 2n = 36, 54, 70, and 72
(Gould 1975b). Disturbed grasslands; Travis (BRIT), Fayette (TAES), Bexar, Caldwell, and
McLennan (Turner et al. 2003) cos. in sw part of East TX; widespread in w 2/3 of TX; AZ, CO,
NM, OK, and TX. May–Nov. [Trichachne californica (Benth.) Chase]
Digitaria ciliaris (Retz.) Koeler, (ciliate, fringed), SOUTHERN CRAB GRASS. Annual; culms decumbent
and rooting at lower nodes, the erect portion to ca. 60 cm tall; similar to D. sanguinalis, differing
in characteristics as enumerated in the key; also similar to D. bicornis but usually dark
green (Webster 1987); inflorescence branches digitately arranged or in whorls; leaf sheaths