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Cusick's bluegrass

Texas bluegrass

Habit Plants perennial; usually densely tufted, rarely moderately densely tufted, usually neither rhizomatous nor stoloniferous, infrequently short-rhizomatous or stoloniferous, rarely with distinct rhizomes. Plants perennial; loosely tufted, rhizomatous, rhizomes slender.
Culms

10-60(70) cm tall, 0.5-1.8 mm thick, erect or the bases decumbent, terete or weakly compressed;

nodes terete, 0-2 exserted.

20-85 cm, erect, terete or weakly compressed;

nodes terete, 0-1 exserted.

Sheaths

closed for 1/4-3/4 their length, terete, smooth or scabrous, glabrous, bases of basal sheaths glabrous, distal sheath lengths 1.6-10 times blade lengths;

collars smooth or scabrous, glabrous;

ligules of cauline leaves 1-3(6) mm, smooth or scabrous, truncate to acute, ligules of the innovation leaves 0.2-0.5(2.5) mm, scabrous, usually truncate;

innovation blades sometimes distinctly different from the cauline blades, 0.5-2 mm wide, involute, moderately thick, moderately firm, adaxial surfaces usually densely scabrous or hispidulous to softly puberulent, infrequently nearly smooth and glabrous;

cauline blades subequal or the midcauline blades longest or the blades gradually reduced in length distally, 0.5-3 mm wide, flat, folded, or involute, usually thin, usually withering, abaxial surfaces smooth or scabrous, apices narrowly to broadly prow-shaped, flag leaf blades 0.5-5(6) cm.

closed firmly for 1/7-1/3 their length, sometimes for a longer distance by a hyaline membrane, terete, smooth, glabrous, bases of basal sheaths glabrous;

ligules 1-4 mm, smooth or scabrous;

innovation blades 10-35 cm long, 1-3.5 mm wide;

cauline blades 2-25 cm long, 1.5-4.5 mm wide, flat or folded, lax, both surfaces smooth or sparsely finely scabrous, glabrous, apices narrowly to broadly prow-shaped.

Basal branching

intravaginal or intra- and extravaginal.

intra- and extravaginal.

Panicles

2-10(12) cm, usually erect, contracted or loosely contracted, narrowly lanceoloid to ovoid, congested or moderately congested, with 10-100 spikelets and 1-3(5) branches per node;

branches 0.5-4(5) cm, erect or steeply ascending, fairly straight, slender to stout, terete to angled, smooth or scabrous, with 1-15 spikelets.

3-12(18) cm, erect, narrowly cylindrical, often interrupted or lobed, congested, with (70)100-200 spikelets;

nodes with (2)3-7(9) branches;

branches 1-3(5) cm, erect to slightly ascending, terete or weakly angled, sparsely to densely coarsely scabrous, with 8-30 spikelets.

Spikelets

(3)4-10 mm, lengths to 3 times widths, broadly lanceolate to narrowly ovate, laterally compressed, not sexually dimorphic;

florets 2-6;

rachilla internodes 0.5-1.2 mm, smooth or scabrous.

4-8(10) mm, sexually dimorphic, laterally compressed, pistillate spikelets larger, with fewer florets and more pubescence than the staminate spikelets;

florets 2-10;

rachilla internodes smooth.

Glumes

lanceolate, distinctly keeled;

lower glumes 3-veined, distinctly shorter than the lowest lemmas;

calluses glabrous or diffusely webbed, hairs less than 1/4 the lemma length;

lemmas (3)4-7 mm, lanceolate to broadly lanceolate, distinctly keeled, membranous to thinly membranous, smooth or sparsely to densely scabrous, glabrous or the keels and/or marginal veins puberulent proximally, lateral veins obscure to prominent, margins glabrous, apices acute;

palea keels scabrous, intercostal regions glabrous;

anthers vestigial (0.1-0.2 mm), aborted late in development, or 2-3.5 mm.

unequal, distinctly keeled, keels and lateral veins scabrous;

lower glumes 1-3-veined.

Pistillate florets

calluses copiously 3-webbed, hairs 4-10 mm, mostly silky, plicate;

lemmas 4.2-6.4 mm, lanceolate, 5-7 veined, distinctly keeled, glabrous, or the keels and marginal veins, sometimes also the lateral veins, densely long-villous, margins glabrous, apices acute;

palea keels scabrous, glabrous or sometimes softly puberulent to long-villous at midlength.

Staminate florets

calluses glabrous or sparsely dorsally webbed, hairs plicate, rarely with additional webs under the marginal veins;

lemmas 3.5-5 mm, lanceolate, distinctly keeled, keels and marginal veins sparsely short- to long-villous, margins glabrous, apices acute;

palea keels scabrous, glabrous or softly puberulent to long-villous at midlength;

anthers vestigial (0.1-0.2 mm) or 1.6-2.7 mm.

2n

= 28, 28+11, 56, 56+11, 59, ca. 70.

= 42, ca. 54, 56, ca. 63, 84.

Poa cusickii

Poa arachnifera

Distribution
from FNA
CA; CO; ID; MT; ND; NV; OR; UT; WA; WY; AB; BC; MB; SK; YT
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; FL; GA; IL; KS; LA; MS; NC; NM; OK; SC; TN; TX
[WildflowerSearch map]
[BONAP county map]
Discussion

Poa cusickii grows in rich meadows in sagebrush scrub to rocky alpine slopes, from the southwestern Yukon Territory to Manitoba and North Dakota, south to central California and eastern Colorado. It is gynodioecious or dioecious.

Sexually reproducing plants of Poa cusickii subspp. cusickii and pallida grow in different geographic areas, but pistillate plants of these two subspecies have overlapping ranges. Only pistillate plants are known in Poa cusickii subspp. epilis and purpurascens. All the alpine plants studied were pistillate.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Poa arachnifera grows on moist, sandy to rich, black bottomlands of the southern Great Plains. At one time it was cultivated for winter pasture in the southeastern United States. It is strictly dioecious, with a 1:1 ratio of staminate to pistillate plants among herbarium samples. The variable and high chromosome numbers suggest it may be apomictic, but the occurrence of equal numbers of staminate and pistillate individuals in populations seems to suggest that reproduction is primarily sexual. It is the only non-South American species in the section. Its closest relatives appear to be P. bonariensis (Lam.) Kunth and P. lanuginosa Poir.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Panicle branches smooth or slightly scabrous, or the basal blades more than 1.5 mm wide and flat or folded; cauline blades more than 1.5 mm wide, often flat; some basal branching extravaginal; lemmas and calluses sometimes sparsely puberulent.
→ 2
2. Lemmas usually glabrous, rarely plants from the Rocky Mountains with puberulent keels and marginal veins; calluses glabrous; panicles erect, usually contracted; branches smooth to slightly scabrous
subsp. epilis
2. Lemmas rarely completely glabrous, at least some florets v/ith sparsely puberulent keels, the marginal veins glabrous or puberulent; calluses frequendy with a sparse, short web; panicles somewhat lax and loosely contracted; branches smooth or sparsely to moderately scabrous
subsp. purpurascens
1. Panicle branches moderately to strongly scabrous; basal and cauline blades usually less than 1.5 mm wide, involute, rarely flat or folded; basal branching intravaginal; lemmas and calluses glabrous.
→ 3
3. Panicle branches longer than 1.7 cm in at least some panicles; panicles open or contracted
subsp. cusickii
3. Panicle branches up to 1.7 cm long, stout; panicles contracted
subsp. pallida
Source FNA vol. 24, p. 559. FNA vol. 24.
Parent taxa Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Epiles Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Dioicopoa
Sibling taxa
P. abbreviata, P. alpina, P. alsodes, P. ammophila, P. annua, P. arachnifera, P. arctica, P. arida, P. arnowiae, P. atropurpurea, P. autumnalis, P. bigelovii, P. bolanderi, P. bulbosa, P. chaixii, P. chambersii, P. chapmaniana, P. compressa, P. confinis, P. curtifolia, P. cuspidata, P. diaboli, P. douglasii, P. eminens, P. fendleriana, P. glauca, P. hartzii, P. howellii, P. infirma, P. interior, P. keckii, P. kelloggii, P. laxa, P. laxa × glauca, P. laxiflora, P. leibergii, P. leptocoma, P. lettermanii, P. macrantha, P. macrocalyx, P. marcida, P. napensis, P. nemoralis, P. nervosa, P. occidentalis, P. paludigena, P. palustris, P. paucispicula, P. piperi, P. porsildii, P. pratensis, P. pringlei, P. pseudoabbreviata, P. reflexa, P. rhizomata, P. saltuensis, P. secunda, P. sierrae, P. stebbinsii, P. stenantha, P. strictiramea, P. sublanata, P. suksdorfii, P. supina, P. sylvestris, P. tenerrima, P. tracyi, P. trivialis, P. unilateralis, P. wheeleri, P. wolfii, P. ×gaspensis, P. ×limosa, P. ×nematophylla
P. abbreviata, P. alpina, P. alsodes, P. ammophila, P. annua, P. arctica, P. arida, P. arnowiae, P. atropurpurea, P. autumnalis, P. bigelovii, P. bolanderi, P. bulbosa, P. chaixii, P. chambersii, P. chapmaniana, P. compressa, P. confinis, P. curtifolia, P. cusickii, P. cuspidata, P. diaboli, P. douglasii, P. eminens, P. fendleriana, P. glauca, P. hartzii, P. howellii, P. infirma, P. interior, P. keckii, P. kelloggii, P. laxa, P. laxa × glauca, P. laxiflora, P. leibergii, P. leptocoma, P. lettermanii, P. macrantha, P. macrocalyx, P. marcida, P. napensis, P. nemoralis, P. nervosa, P. occidentalis, P. paludigena, P. palustris, P. paucispicula, P. piperi, P. porsildii, P. pratensis, P. pringlei, P. pseudoabbreviata, P. reflexa, P. rhizomata, P. saltuensis, P. secunda, P. sierrae, P. stebbinsii, P. stenantha, P. strictiramea, P. sublanata, P. suksdorfii, P. supina, P. sylvestris, P. tenerrima, P. tracyi, P. trivialis, P. unilateralis, P. wheeleri, P. wolfii, P. ×gaspensis, P. ×limosa, P. ×nematophylla
Subordinate taxa
P. cusickii subsp. cusickii, P. cusickii subsp. epilis, P. cusickii subsp. pallida, P. cusickii subsp. purpurascens
Name authority Vasey Torr.
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