Poa pratensis |
Poa unilateralis |
|||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Kentucky blue grass |
ocean bluff blue grass, San Francisco bluegrass, sea-bluff bluegrass |
|||||||||||||||||||||||||
Habit | Plants perennial; green or anthocyanic, sometimes glaucous; extensively rhizomatous, densely to loosely tufted or the shoots solitary. | Plants perennial; frequently glaucous; densely tufted, not stoloniferous, not rhizomatous. | ||||||||||||||||||||||||
Culms | 5-70(100) cm, erect or the bases decumbent, not branching above the base, terete or weakly compressed; nodes terete or weakly compressed, 1-2(3) exposed, proximal node(s) usually not exserted. |
5-40 cm, erect or ascending, frequently decumbent, terete, with 0-2 exserted nodes. |
||||||||||||||||||||||||
Sheaths | closed for 1/4-1/2 their length, terete to slightly compressed, glabrous or infrequently sparsely to moderately hairy, bases of basal sheaths glabrous, not swollen, distal sheath lengths 1.2-5(6.2) times blade lengths; collars smooth, glabrous; ligules 0.9-2(3.1) mm, smooth or scabrous, truncate to rounded, infrequently obtuse, ciliolate or glabrous; blades of extravaginal innovations like those of the culms, those of the intravaginal shoots sometimes distinctly narrower, 0.4-1 mm wide, flat to involute; cauline blades 0.4-4.5 mm wide, flat, folded, or involute, soft and lax to moderately firm, abaxial surfaces smooth, glabrous, adaxial surfaces smooth or sparsely scabrous, frequently sparsely hairy, hairs 0.2-0.8 mm, erect to appressed, slender, curving, sinuous or straight, apices usually broadly prow-shaped, sometimes narrowly prow-shaped, blades subequal, the middle blades longest, the flag leaf blades 1.5-10 cm. |
closed for 1/10(1/5) their length, terete, smooth, glabrous, bases of basal sheaths glabrous, distal sheath lengths 1-4 times widths; ligules 2-6 mm, smooth or sparsely scabrous, obtuse to acute; innovation blades usually 1-1.5 mm wide, thin, soon withering, and distinctly narrower than the cauline blades, infrequently wider, flat, and a bit fleshy as in the cauline blades, or involute; cauline blades gradually reduced in length distally, 2-5 mm wide, flat or folded, soft, thin and soon withering or moderately thick and somewhat fleshy and retaining their form, smooth, apices narrowly to broadly prow-shaped. |
||||||||||||||||||||||||
Basal branching | mainly extravaginal or evenly extra- and intravaginal. |
all or mainly intravaginal. |
||||||||||||||||||||||||
Panicles | 2-15(20) cm, narrowly ovoid to narrowly or broadly pyramidal, loosely contracted to open, sparse to moderately congested, with (25) 30-100+ spikelets and (1)2-7(9) branches per node; branches (1)2-9 cm, spreading early or late, terete or angled, smooth or sparsely to moderately densely scabrous, with 4-30(50) spikelets usually fairly crowded in the distal 1/2. |
3-7 cm, erect, nearly cylindrical, contracted, congested, with (20)30-80(120) spikelets; nodes with 3-7 branches; branches 0.5-1.5(4.5) cm, erect, usually angled, infrequently terete or sulcate, angles usually moderately to densely scabrous, infrequently smooth with dense papillae and weak-angled, with 2-10 spikelets in the proximal 2/3; pedicels shorter than the spikelets. |
||||||||||||||||||||||||
Spikelets | 3.5-6(7) mm, lengths 3.5 times widths, laterally compressed, sometimes bulbiferous; florets 2-5, usually normal, sometimes bulb-forming; rachilla internodes usually shorter than 1 mm, smooth, glabrous. |
4.5-7 mm, lengths to 3.5 times widths, lanceolate to narrowly ovate, drab; florets 3-5; rachilla internodes usually shorter than 1 mm, smooth. |
||||||||||||||||||||||||
Glumes | unequal to subequal, usually distinctly shorter than the adjacent lemmas, narrowly lanceolate to lanceolate, infrequently broadly lanceolate, distinctly keeled, keels usually sparsely to densely scabrous, infrequently smooth; lower glumes 1.5-4(4.5) mm, usually narrowly lanceolate to lanceolate, occasionally sickle-shaped, 1-3-veined; upper glumes 2-4.5(5) mm, distinctly shorter than to nearly equaling the lowest lemmas; calluses dorsally webbed, sometimes with additional webs below the marginal veins, hairs at least 1/2 as long as the lemmas, crimped; lemmas 2-4.3(6) mm, lanceolate, green or strongly purple-tinged, distinctly keeled, keels and marginal veins long-villous, lateral veins usually glabrous, infrequently short-villous to softly puberulent, lateral veins prominent, intercostal regions glabrous, lower portion smooth or finely muriculate, upper portion smooth or sparsely scabrous, margins narrowly to broadly hyaline, glabrous, apices acute; paleas scabrous, keels sometimes softly puberulent, intercostal regions narrow, usually glabrous, rarely sparsely hispidulous; anthers usually 1.2-2 mm, infrequently aborted late in development. |
lanceolate, slightly unequal, distinctly keeled, keels papillate or scabrous; lower glumes 3-veined; calluses glabrous or with a crown of hairs, hairs 0.1-0.2 mm; lemmas 3-4.5 mm, lanceolate, distinctly keeled, glabrous or the keels and marginal veins short-villous to midlength, intercostal regions sparsely puberulent near the base, margins glabrous, apices acute; palea keels scabrous, sometimes softly puberulent at midlength; anthers 1.5-3 mm. |
||||||||||||||||||||||||
2n | = 27, 28, 32, 35, 37, 41-46, 48-147. |
= 42, 84. |
||||||||||||||||||||||||
Poa pratensis |
Poa unilateralis |
|||||||||||||||||||||||||
Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; HI; PR; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Greenland
|
CA; OR; WA
|
||||||||||||||||||||||||
Discussion | Poa pratensis is common, widespread, and well established in many natural and anthropogenic habitats of the Flora region. The only taxa that are clearly native to the region are the arctic and subarctic subspp. alpigena and colpodea. Outside the Flora region, P. pratensis is native in temperate and arctic Eurasia. It is now established in temperate regions around the world. Poa pratensis is a highly polymorphic, facultatively apomictic species, having what is probably the most extensive series of polyploid chromosome numbers of any species in the world. Poa pratensis is a hybridogenic species, i.e., it comprises numerous lineages with the same basic maternal genome, but different paternal genomes. The lineages are perpetuated by agamospermic and vegetative reproduction. Some major forms are recognized as microspecies or subspecies. These have some correlated ecological and morphological differences, but the morphological boundaries between them are completely bridged, and in some cases the taxa (e.g., subspp. agassizensis and colpodea) may represent environmentally induced plasticity. Natural hybrids have been identified between Poa pratensis and P. alpina, P. arctica, P. wheeleri, and P. secunda. Many other artificial hybrids have been made; these involve many different, often distantly related, species. In addition, there are many cultivated forms of the species; these have been seeded widely throughout the Flora region for lawns, soil stabilization, and forage. Most cultivated forms favor subsp. irrigata morphologically; others tend towards subspp. pratensis and angustifolia, the latter occurring most commonly in xeric sites. Poa rhizomata (p. 546) resembles P. pratensis, but has acute ligules arid sparse inflorescences, florets that are usually unisexual, and generally larger spikelets; Poa macrocalyx (p. 527) looks like a robust P. pratensis with large spikelets, and lemmas and paleas that are generally hispidulous between the veins and palea keels. Poa confinis (p. 552) also resembles P. pratensis, but differs in having glabrous or sparsely hairy lemmas, and diffusely webbed calluses. Cultivars of Poa pratensis Plants densely to loosely tufted, often forming turf, shoots clustered. Basal branching intra- and extravaginal or mainly extravaginal. Culms 8-50 cm. Innovation shoot blades usually shorter than 45 cm, (0.4)1-4 mm wide, usually flat, sometimes some involute, usually soft, sometimes somewhat firm, adaxial surfaces usually glabrous; cauline blades flat or folded. Panicles 3-15 cm, broadly pyramidal, open or somewhat contracted, with 2-7(9) branches per node; branches ascending or widely spreading, sparsely to densely scabrous, with few to many spikelets per branch. Spikelets lanceolate to broadly lanceolate, not bulbiferous; florets normal. Glume keels strongly compressed, sparsely to moderately scabrous; upper glumes shorter than to nearly equaling the lowest lemmas; lemmas 2.8-4.3(6) mm, finely muriculate, lateral veins glabrous; palea keels scabrous, glabrous, intercostal regions glabrous. 2n = 41-45, 48-59, 62, 64-74, 76, 78, 80, 81, 84-90, 95. More than 60 cultivars of Poa pratensis have been released in the Flora region. Plants grown from commercially distributed seed have generally been placed in subsp. pratensis by North American authors, but they appear to include genetic contributions from at least three major subspecies, e.g., subspp. angustifolia, pratensis, and irrigata. These and intermediate forms, especially those favoring subspp. irrigata and pratensis, are best simply referred to as Poa pratensis sensu lato or labeled as cultivated material.The chromosome counts listed here are numbers reported for the species that are probably not subspp. alpigena, angustifolia, or colpodea; they may represent subspp. irrigata or pratensis. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa unilateralis grows on grassy bluffs and cliffs near the Pacific coast of North America, from Washington to California. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
||||||||||||||||||||||||
Key |
|
|
||||||||||||||||||||||||
Source | FNA vol. 24, p. 522. | FNA vol. 24, p. 594. | ||||||||||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Poa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Secundae > subsect. Halophytae | ||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||
Subordinate taxa | ||||||||||||||||||||||||||
Name authority | L. | Scribn. | ||||||||||||||||||||||||
Web links |
|