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

1036 POACEAE/POA
2. Plants perennial, 15–100 cm tall, with OR without rhizomes; keel of glumes minutely to strongly
scabrous-ciliate.
5. Plants with slender creeping rhizomes; lemmas acute or with awn-like tip, pubescent only
on keel or marginal veins; inflorescence branches tightly contracted to somewhat spreading,
� densely-flowered, often with flowers nearly to base but sometimes naked of spikelets in
their lower half; plants of various habitats, including grasslands and other open areas.
6. Culms and basal leaf sheaths strongly flattened, sharply keeled; species rare in East TX
______________________________________________________________________ P. compressa
6. Culms and basal leaf sheaths terete or only slightly flattened, not sharply keeled; including
species widespread in East TX.
7. Lower lemmas of each spikelet 3.9–6.4 mm long; lowest node of inflorescence usually
with (2–)3–4 branches, the branches often, but not always, bearing spikelets to
the base or nearly so; plants with unisexual florets; species of undisturbed habitats,
widespread in East TX __________________________________________________ P. arachnifera
7. Lower lemmas of each spikelet usually 2.5–3.2 mm long; lowest node of inflorescence
usually with (4–)5 branches, the branches naked basally; plants with perfect
florets; species of disturbed habitats, known primarily from n part of East TX (Brazos,
Dallas, Fannin, Grayson, Lamar, Nacogdoches, and San Augustine cos.) ______________ P. pratensis
5. Plants without rhizomes; lemmas subacute or obtuse, pubescent at least on proximal surface
(as well as on keel and marginal veins), sometimes over the entire surface; inflorescence
branches widely spreading, loosely-flowered, naked of spikelets for half to four-fifths
their length; plants of wooded habitats.
8. Lowest node of inflorescence usually with 3–7 branches; spikelets 3–4.5 mm long; lemmas
with long, kinky, cobwebby hairs at base ____________________________________ P. sylvestris
8. Lowest node of inflorescence usually with 2 branches; spikelets usually 5–8 mm long;
lemmas without long hairs at base but long-pubescent on margins and keel ________ P. autumnalis
Poa annua L., (annual, yearly), ANNUAL BLUEGRASS, LOW SPEAR GRASS, DWARF MEADOW GRASS.
Glabrous tufted annual; culms usually geniculate, to ca. 30 cm long; inflorescences small, (1–)
3–8(–10) cm long, erect, at least the lower branches spreading; spikelets 2.5–5.5 mm long; lemmas
long-pubescent on margins and keel. Disturbed sites, lawns; widespread in e 1/2 of TX,
scattered further w; throughout most of Canada and the U.S. Jan–May, occasionally as early as
late fall. Native of Europe and Asia. [P. annua L. var. reptans Hausskn.] This weedy species is now
distributed nearly worldwide, and Tucker (1996) indicated that it has “perhaps the widest distribution
of any angiosperm.” Clayton and Renvoize (1986) noted that it is “probably the most
cosmopolitan of all grass species.” The pollen is allergenic. I
Poa arachnifera Torr., (spider-bearing, its long white hairs giving the appearance of a spider
web), TEXAS BLUE GRASS. Sod-forming, glabrous perennial with long slender rhizomes; culms
20–60(–85) cm tall; inflorescences 3–15(–18) cm long, dense, rather narrow, erect; spikelets ca.
(4–)6–8(–9) mm long; florets unisexual, the sexes on different plants (bisexual florets rarely
found); lemmas of pistillate spikelets with long-ciliate keel and dense basal tuft of long, cobwebby
hairs; lemmas of staminate spikelets with keel inconspicuously ciliate toward base and
rather sparse basal tuft of cobwebby hairs. Calcareous or sandy clay prairies and oak openings,
primarily undisturbed areas; widespread in TX but less common in far e, far s, and Trans-Pecos;
native of KS, OK, and TX (Soreng & Kellogg ined.) but now found more widely—se U.S. from NC s
to FL w to NM, also IL and KS. Late Mar–Apr. This species is frequent in original prairie, though
not abundant; it increases under light disturbance and disappears early under heavy grazing.
Poa autumnalis Muhl. ex Elliott, (autumnal, of the fall), AUTUMN BLUE GRASS, FLEXUOUS SPEAR
GRASS. Tufted perennial 30–75(–86) cm tall; inflorescences open, the branches usually spreading
at maturity, the lower branches with spikelets only near the tips; spikelets usually 5–8 mm