Poa

 Kentucky bluegrass Poa pratensis, photographed by Russ Kleinman & Kelly Kindscher.

Belongs within: Pooideae.

Poa is a genus of more than 500 species of grasses, including meadow-grasses and bluegrasses, found in temperate regions of both hemispheres as well as on tropical mountains. Notable species include P. annua, annual bluegrass, which is commonly used for lawns and animal fodder.

The greater number of species are perennial though members of the sections Ochlopoa and Diversipoa are largely annual. Spikelets of Ochlopoa have the callus glabrous whereas in Diversipoa it bears cobwebby hairs. Poa compressa is a rhizomatous perennial with distinctly compressed, wiry stems and nodes (Hickman 1993).

Characters (from Zhu, Liu et al.): Annuals or perennials. Culm bases infrequently swollen, or with bulbous sheath bases; new shoots intravaginal, extravaginal, or pseudointravaginal, intravaginal but with reduced or rudimentary lower leaf blades and weakly differentiated prophyl. Uppermost culm leaf sheath closed from 1/20th to entire length; ligule hyaline, membranous or infrequently papery; blade flat, folded, or involute, abaxially keeled, adaxially with 1 groove on either side of the midvein, apex prow-tipped. Inflorescence a terminal panicle; branches 1–9 per node; flowers all bisexual, or mixed bisexual and female (rarely male), with distal female flowers within spikelets, or with partially to wholly female spikelets or inflorescences. Spikelets laterally compressed, florets (1–)2–8(–10), rachilla disarticulating above glumes and between florets, uppermost floret vestigial; vivipary sometimes present; glumes mostly strongly keeled, unequal, or subequal, lower glume 1- or 3-veined, upper glume 3(or 5)-veined; lemmas laterally compressed, usually distinctly keeled, 5(–7)-veined, distal margins and apex membranous, apex awnless, rarely minutely mucronate; floret callus short, truncate, blunt, glabrous or webbed (with a dorsal tuft of woolly hairs), rarely with a line of hairs around base of lemma; palea subequal or infrequently to 2/3 as long as lemma, not gaping, keels green, distinctly separated, usually scabrid, sometimes smooth, sometimes pilulose to villous, margins usually smooth, glabrous. Lodicules 2. Stamens 3, anthers sometimes vestigial. Ovary glabrous. Caryopsis oblong to fusiform, triangular to oval in cross section, sometimes grooved, free or adhering to the palea. 2n = 14–266. x = 7.

<==Poa
|--P. × limosa [P. pratensis × P. secunda ssp. juncifolia; incl. P. fibrata]H93
|--P. nervosa complexH93
| |--P. rhizomataH93
| `--P. sierraeH93
|--P. (sect. Poa) pratensisH93
| |--P. p. ssp. pratensisH93
| |--P. p. ssp. agassizensisH93
| `--P. p. ssp. angustifoliaH93
|--P. sect. AbbreviataeH93
| |--P. keckiiH93
| |--P. lettermaniiH93
| `--P. pattersoniiH93
|--P. (sect. Coenopoa) trivialisH93
|--P. sect. DiversipoaH93
| |--P. bigeloviiH93
| |--P. bolanderiH93
| `--P. howellii [=P. bolanderi ssp. howellii]H93
|--P. sect. MadropoaH93
| | i. s.: P. atropurpureaH93
| | P. confinisH93
| | P. douglasiiH93
| | P. fendlerianaH93
| | |--P. f. ssp. fendlerianaH93
| | `--P. f. ssp. longiligulaH93
| | P. macrantha [=P. douglasii ssp. macrantha]H93
| | P. piperiH93
| `--P. subsect. EpilesH93
| |--P. cusickiiH93
| | |--P. c. ssp. cusickii [incl. P. hansenii]H93
| | |--P. c. ssp. epilisH93
| | |--P. c. ssp. pallidaH93
| | `--P. c. ssp. purpurascensH93
| |--P. pringleiH93
| `--P. stebbinsiiH93
|--P. sect. OchlopoaH93
| |--P. annuaH93
| `--P. infirmaH93
|--P. (sect. Oreinos) leptocomaH93
|--P. sect. SecundaeH93
| | i. s.: P. secundaH93
| | |--P. s. ssp. secunda [incl. P. canbyi, P. gracillima, P. incurva, P. sandbergii, P. scabrella]H93
| | `--P. s. ssp. juncifolia [incl. P. ampla, P. nevadensis]H93
| | P. tenerrimaH93
| `--P. subsect. HalophytaeH93
| |--P. napensisH93
| `--P. unilateralis [incl. P. pachypholis]H93
|--P. sect. StenopoaH93
| |--P. glaucaH93
| | |--P. g. ssp. glaucaH93
| | `--P. g. ssp. rupicolaH93
| |--P. nemoralisH93
| | |--P. n. var. nemoralisD03
| | `--P. n. var. magellanicaD03
| `--P. palustrisVB02
`--P. (sect. Tichopoa) compressaH93

Poa incertae sedis:
P. acicularifoliaW27
P. aitchisonii Boiss. 1884SS05
‘Agrostis’ albaV72
P. alpigenaO88
|--P. a. ssp. alpigenaO88
`--P. a. ssp. staintoniiO88
P. alpinaV72 [=P. anceps var. alpinaC06, P. caespitosa var. alpinaB78]
P. alsodesV72
P. anceps [incl. P. anceps var. elata, P. anceps var. foliosa non Festuca foliosa]C06
|--P. a. var. ancepsA27
|--P. a. var. condensata Cheeseman 1906C06
|--P. a. var. debilisA27
|--P. a. var. densifloraA27
`--P. a. var. gracilis Cheeseman 1906C06
P. arcticaH44
P. arnoldiiO88
P. astoni Petrie 1906C06
P. attenuata Trin. 1835SS05
P. australis Br. 1810G52 (see below for synonymy)
|--P. a. var. australisC06
|--P. ‘caespitosa’ var. latifoliaB78
`--P. ‘caespitosa’ var. leioclada Hackel in Cheeseman 1906C06
P. autumnalisV72
P. bonariensisS06
P. brevifoliaJ23
P. breviglumisW91
P. bulbosa Linnaeus 1753PL04
|--P. b. var. bulbosaO88
`--P. b. var. viviparaO88
P. calliopsisO88
P. celsaW91
P. chathamica Petrie 1902C06
P. cheesemanii Hackel 1903C06
P. ciliarisC55b
P. clelandiiB00
P. colensoiW91
|--P. c. var. colensoiC06
`--P. c. var. intermedia Cheeseman 1906C06
P. cookiiSBG97
P. dipsacea Petrie 1894C06
P. drummondiana Nees 1843G52 [incl. P. brizochloa Muell. 1855B78, P. cognataG52, P. nodosaG52]
P. eleanoraeO88
P. ensiformisB00
P. eragrostisC55a
P. exiguaA27
P. falconeriO88
P. fawcettiaeB00
P. flabellata [incl. Dactylis caespitosa]C06
P. foliosa [=Festuca foliosa]C06
P. fuegianaD03
P. grisebachii Fries 1905S06
P. gunniiB00
P. hamiltoni Kirk 1895C06
P. hiemataB00
P. himalayanaO88
P. hirtiglumisO88
P. holciformisS06
P. homomallaB78
P. hookeriB00
P. imbecillaC06 [=Eragrostis imbecillaC06; incl. P. sprengeliiB78]
|--P. i. var. imbecillaC06
`--P. i. var. matthewsii (Petrie) Hackel in Cheeseman 1906C06 (see below for synonymy)
P. imperialisO88
P. inconspicua Veldkamp in Royen 1979GR98
P. incrassata Petrie 1902C06
P. interior [=P. nemoralis var. interior]V72
P. kanaii Rajbh. 1988SS05
P. kelloggiiH93
P. kirkii [incl. P. purpurea Kirk 1877 (n. n.)]C06
|--P. k. var. kirkiiC06
|--P. k. var. collinsii Hackel in Cheeseman 1906 [=P. collinsii Kirk ex Petrie 1896 (n. n.)]C06
`--P. k. var. mackayi (Buchanan) Hackel in Cheeseman 1906C06
P. labillardieriB00
P. langtangensisO88
P. languidaV72
P. lanuginosaS06
P. lepida Muell. 1873G52
P. ligularisRJ11
P. lindsayiC06
P. litorosa Cheeseman 1906 [=Festuca scoparia non Poa scoparia]C06
P. ludensO88
P. maiaW91
P. maniototo Petrie 1890C06
P. maroccanaGR98
P. maxwelli Benth. 1878G52
P. morrisiiB00
P. myriantha Hackel in Stuckert 1906S06
P. novae-zealandiae Hack. 1903C06
|--P. n. var. novae-zealandiaeC06
`--P. n. var. subvestita Hack. 1903C06
P. pagophilaSS05
P. paludigenaV72
P. × perinconspicua Scholz in Greuter & Raus 1998 (see below for synonymy)GR98
P. poaeformis (Labill.) Druce 1917 [=Arundo poaeformis; incl. P. australis var. billardieri]G52
P. polycoleaO88
P. polyphylla Hack. 1903C06
P. poophagorumO88
P. pusilla Berggr. 1877 [incl. P. anceps var. minima]C06
P. pygmaeaW27
P. queenslandicaB00
P. quinquefidaJ23
P. ramosissimaC06
P. rodwayiB00
P. saltuensisV72
P. saxicolaMB08
P. scaberulaD03
P. sclerophylla Berggr. 1877 [incl. P. albida]C06
P. seticulmis Petrie 1902C06
P. sieberianaB00
P. sikkimensisO88
P. stapfianaO88
P. suksdorfiiH93
P. sylvestrisV72
P. teneraB00 [=P. caespitosa var. teneraB78; incl. P. effusaB78]
P. unifloraA27
P. wheeleriH93

Poa australis Br. 1810G52 [=P. caespitosa var. australisB78; incl. P. caespitosa var. affinisB78, G52, P. caespitosaG52, P. laevis var. filifoliaC06, P. implexaB78, P. australis var. laevisC06, G52, P. caespitosa var. laevisB78, P. caespitosa var. plebeiaB78, G52, P. porphyrocladosB78, P. caespitosa var. serpentumB78, G52, P. sieberianaB78]

Poa imbecilla var. matthewsii (Petrie) Hackel in Cheeseman 1906C06 [=P. matthewsii Petrie 1902C06; incl. P. anceps var. breviculmisA27, C06]

Poa × perinconspicua Scholz in Greuter & Raus 1998 [P. maroccana × P. infirma; =P. × inconspicua Scholz 1995 non Veldkamp in Royen 1979]GR98

*Type species of generic name indicated

References

[A27] Andersen, J. C. 1927. Popular names of New Zealand plants. Part 2. Transactions and Proceedings of the New Zealand Institute 57: 905–977.

[B78] Bentham, G. 1878. Flora Australiensis: A description of the plants of the Australian Territory vol. 7. Roxburghiaceae to Filices. L. Reeve & Co.: London.

[B00] Braby, M. F. 2000. Butterflies of Australia: their identification, biology and distribution vol. 2. CSIRO Publishing: Collingwood (Victoria).

[C55a] Candolle, A. de. 1855a. Géographie Botanique Raisonée: Ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle vol. 1. Librairie de Victor Masson: Paris.

[C55b] Candolle, A. de. 1855b. Géographie Botanique Raisonée: Ou exposition des faits principaux et des lois concernant la distribution géographique des plantes de l’époque actuelle vol. 2. Librairie de Victor Masson: Paris.

[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.

[D03] Dusén, P. 1903. The vegetation of western Patagonia. In: Scott, W. B. (ed.) Reports of the Princeton University Expeditions to Patagonia, 1896–1899 vol. 8. Botany pp. 1–34. The University: Princeton (New Jersey).

[G52] Gardner, C. A. 1952. Flora of Western Australia vol. 1 pt 1. Gramineae. William H. Wyatt: Perth.

[GR98] Greuter, W., & T. Raus (eds.) 1998. Med-Checklist Notulae, 17. Willdenowia 28: 163–174.

[H44] Hammer, M. 1944. Studies on the oribatids and collemboles of Greenland. Meddelelser om Grønland 141 (3): 1–210.

[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

[J23] James, E. 1823. Account of an Expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and ’20, by order of the Hon. J. C. Calhoun, sec’y of war: under the command of Major Stephen H. Long. From the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party vol. 1. H. C. Carey & I. Lea: Philadelphia.

[MB08] Maiden, J. H., & E. Betche. 1908. Notes from the Botanic Gardens, Sydney. No. 13. Proceedings of the Linnean Society of New South Wales 33: 304–319.

[O88] Ohba, H. 1988. The alpine flora of the Nepal Himalayas: an introductory note. In: Ohba, H., & S. B. Malla (eds) The Himalayan Plants vol. 1. The University Museum, University of Tokyo, Bulletin 31: 19–46.

[PL04] Pohl, G., & I. Lenski. 2004. Zur Verbreitung und Vergesellschaftung von Pennisetum orientale Rich. in Nordeuböa (Griechenland) (Poaceae, Paniceae). Senckenbergiana Biologica 83 (2): 209–223.

[RJ11] Rising, J. D., A. Jaramillo, J. L. Copete, P. G. Ryan & S. C. Madge. 2011. Family Emberizidae (buntings and New World sparrows). In: Hoyo, J. del, A. Elliott & D. A. Christie (eds) Handbook of the Birds of the World vol. 16. Tanagers to New World Blackbirds pp. 428–683. Lynx Edicions: Barcelona.

[SS05] Srivastava, S. K., & K. C. Sekar. 2005. Contribution to the flora of Himachal Pradesh from Pin Valley National Park. Bulletin of the Botanical Survey of India 47: 159–162.

[SBG97] Starý, J., W. Block & P. Greenslade. 1997. Oribatid mites (Acari: Oribatida) of sub-Antarctic Heard Island. Journal of Natural History 31: 545–553.

[S06] Stuckert, T. 1906. Segunda contribución al conocimiento de las gramináceas Argentinas. Anales del Museo Nacional de Buenos Aires, serie 3, 6: 409–555.

[VB02] Vijay, S. K., & T. N. Bhardwaja. 2002. Vegetation and phenodynamics of wetlands of central Rajasthan. Journal of the Bombay Natural History Society 99 (3): 573–581.

[V72] Voss, E. G. 1972. Michigan Flora. Part I. Gymnosperms and Monocots. Cranbrook Institute of Science and University of Michigan Herbarium.

[W27] Wall, A. 1927. Some problems of distribution of indigenuous plants in New Zealand. Transactions and Proceedings of the New Zealand Institute 57: 94–105.

[W91] Williams, P. A. 1991. Subalpine and alpine vegetation of granite ranges in western Nelson, New Zealand. New Zealand Journal of Botany 29: 317–330.

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