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Published In: Species Plantarum 1: 67. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 6/2/2011)
Acceptance : Accepted
Project Data     (Last Modified On 6/3/2011)
General/Distribution: A genus of about 200 species; cosmopolitan, but mainly in temperate regions particularly of the northern hemisphere; 29 species occur in Pakistan, 1 of them only in cultivation.
Comment/Acknowledgements: A very difficult genus to name, partly on account of the wide range of variation displayed by the species, and partly because many of them are extremely closely related. Numerous rather cryptic characters (anther length, presence or absence of wool on the callus, pubescence of lemma body and palea keels, scabridity of panicle branches, length of ligule) have, of necessity, to be employed in the key, but the distinctions between several of the species must at sometime be re-examined on a biosystematic basis. The-problematical species will be apparent from the key which itself is still far from being fool-proof. It must be stressed that entire specimens complete with the basal parts are required for accurate determination and any reference to characteristics of the lemma refer always to the lowermost of a spikelet.

Two species allied to Poa pratensis have been reported from Pakistan but the presence of neither can be confirmed.Poa compressa Linn. differs by its strongly compressed stems and leaf-sheaths. In Flora Iranica (p. 35) Bor says of it, “Mountain sides in India and Pakistan, meadows in Europe,” but no material is cited. Poa alpigena (Blytt) Lindm. is very much like Poa pratensis but has a more slender habit, narrower leaves and a characteristically curved base. Furthermore, the paleakeels are ciliate below. The only specimen cited for Pakistan by Bor (Stainton 2957), however, lacks the essential feature of ciliate palea-keels and has therefore been accommodated in Poa pratensis in this Flora.


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Annuals or perennials. Leaf-blades usually flat, often with a blunt or hooded tip. Inflorescence an open or contracted panicle. Spikelets 2-several-flowered, laterally compressed; glumes subequal or unequal, 1-3-nerved, keeled, usually glabrous; lemmas deeply concave, keeled on the back, membranous but often with hyaline margins, 5-7-nerved, awnless; callus short, obtuse, often with loose woolly hairs; ovary glabrous, the hilum basal and punctiform.

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1.Annual or sometimes perennial, keels of palea with flexuous, curved or crispate hairs along their whole length (or almost so)
2.Lower panicle-branches erecto-patent after anthesis; spikelets with rather distant florets; anthers 0.2-0.5 mm long, scarcely longer than wide
Poa infirma
2.Lower panicle-branches spreading or deflexed after anthesis; spikelets with crowded florets; anthers 0.6-2mm long, at least twice as long as wide
3.Spikelets crowded towards the ends of the panicle-branches; anthers usually 1.3-2 mm long, 5-8 times as long as wide
Poa supina
3.Spikelets not crowded towards the ends of the panicle-branches; anthers 0.6-0.8 (-1) mm long, 2-3 times as long as wide
4.Lemma with copious wool at the base
Poa nepalensis
4.Lemma without any wool at the base
Poa annua
1.Perennial or rarely annual; keels of palea scabrid or prickly, if hairy then only in the lower half
5.Stem with a bulbous swelling at the base formed from the hardened remains of old leaf-sheaths
6.Lemma entirely hairless though often scabrid
Poa bactriana
6.Lemma ciliate, or at least thinly hairy, on the keel and marginal nerves
7.Lemma with wool at the base, this usually copious; lemmas 2.5-3.5mm long; anthers 1-1.5mm long (or spikelets usually proliferating and these characters not visible)
Poa bulbosa
7.Lemma without wool at the base (or sometimes just 1 or 2 strands); lemmas 3.5-5mm long; anthers 1.5-2.5mm long (spikelets rarely proliferating in our area)
Poa sinaica
5.Stem not bulbous at the base, but sometimes thickened with the scarious or fibrous (not hardened) remains of old leaf-sheaths
8.Robust perennial up to 120 cm high; lemma entirely glabrous; panicle narrow; species only in cultivation
Poa ampla
8.Plant not as above; if lemma glabrous then plant not over 40cm high and panicle ovate or pyramidal; native wild specie
9.Lemma hairy on the surface between the nerves (this may be extremely sparse) or sometimes only shortly asperulous
10.Palea-keels ciliate below, scabrid above
11.Stoloniferous plant with culms often ascending from a procumbent base which sometimes roots from the lower nodes; panicle loose, 12-25cm long
Poa stapfiana
11.Tufted plants without stolons; culms not rooting from the lower nodes; panicle lax or dense
12.Spikelets, when young, broadly ovate; leaf-blades 4-12cm long, 2-5mm wide; panicle compact or spreading, 3-7cm long; culms clothed at the base with the fibrous remains of old leaf-sheaths
Poa alpina
12.Spikelets, when young, elliptic or lanceolate; leaf-blades up to 6cm long and 1.5mm wide; panicle contracted, 0.5-5cm long; culms clothed at the base with the scarious remains of old leaf-sheaths
13.Dwarf plants up to 10(-15)cm high; wool present at the base of the lower lemmas; leaf blades up to 2cm long
Poa koelzii
13.Taller plants up to 30 cm high; wool absent or extremely sparse; leaf-blades 2-6cm long
Poa lahulensis
10.Palea-keels scabrid throughout their length.
14.Tufted plants with rhizomes; panicle contracted, spike-like; lemma asperulous all over the back; palea-keels with prickles below and teeth above
Poa tibetica
14.Tufted plants without rhizomes, though sometimes with stolons; panicle lax or effuse, not spike-like; lemmas shortly hairy or with a felty pubescence between the nerves below; palea-keels evenly scabrid or prickly
15.Lower glume subulate-acuminate in side-view, 1-nerved; lemmas obtuse; plant stoloni¬ferous
Poa polycolea
15.Lower glume elliptic or oblong, 1-3-nerved; lemmas acute or obtuse; plant tufted, the culms sometimes decumbent at the base and rooting from the lower nodes, but the plant not other-wise spreading by stolons
16.Slender grass; lemmas very blunt, scabrid on the back and with either a few short hairs or a felty pubescence between the nerves below; spikelets ovate-elliptic, up to 5.5mm long
Poa pagophila
16.Robust grass; lemmas acute, gland-pitted on the back and with short, rather coarse hairs below; spikelets 7-8mm long, the florets eventually widely diverging
Poa falconeri
9.Lemma glabrous on the surface between the nerves although the keel and marginal nerves are usually ciliate below
17.Palea-keels ciliate below, scabrid above
18.Base of the lemma without any wool
Poa sikkimensis
18.Base of the lemma with copious wool
Poa stewartiana
17.Palea-keels scabrid ± throughout their length
19.Plants rhizomatous
20.Lemmas very broad, not strongly keeled on the back, rounded and broadly hyaline at the tip
Poa calliopsis
20.Lemmas strongly keeled on the back, acute or narrowly obtuse at the tip, narrowly hyaline at most
21.Uppermost node in the basal third of the culm; plant densely tufted from a short thick rhizome
Poa versicolor subsp. araratica
21.Uppermost node in the median third of the culm or above; plant loosely or densely tufted from a slender rhizome
22.Panicle narrow, few-spiculate, the branches 2-3 at the lower nodes; ligule 1.5-3mm long (if ligule not more than 1 mm see 21. P. nemoralis)
Poa sterilis
22.Panicle lanceolate to ovate, with many spikelets, often rather dense, with 3-5 branches at the lower nodes; ligule 1-3mm long (if ligule 3.5-10 mm long see 20. P. trivialis)
Poa pratensis
19.Plants not rhizomatous
23.Anthers 0.6-0.75 mm long
Poa setulosa
23.Anthers 1.3-2.5mm long
24.Ligule pointed, 3.5-10 mm long
Poa trivialis
24.Ligule pointed or blunt, not more than 3mm long
25.Ligule very short, scarcely exceeding 1mm in length
26.Anthers 1.3-2mm long; lower glume 3-nerved; panicle-branches scaberulous, 2-5 at the lower nodes
Poa nemoralis
26.Anthers 1.8-2.5 mm long; lower glume 1-nerved; panicle-branches smooth, paired at the lower nodes
Poa aitchisonii
25.Ligule longer, 1-3 mm long
27.Tall plant, usually 40-120cm high; spikelets ovate or oblong, not becoming wedge-shaped; panicle ample, 10-20(-30)cm long, with branches in distant clusters of 3-6 at a node
Poa palustris
27.Smaller plants, but sometimes reaching 40cm in height; spikelets often becoming wedge-shaped; panicle not ample, either short (2-10cm long) and dense or longer (7-15cm long) but with relatively few spikelets
28.Plant stoloniferous, the culms erect or geniculately ascending from a creeping base; panicle very loose and spreading
Poa polycolea
28.Plant tufted, not stoloniferous, the culms usually erect; panicle narrow, lax or dense
29.Uppermost node in the median third of the culm
Poa sterilis
29.Uppermost node in the basal third of the culm
30.Lowest lemma (2-)2.3-3(-3.2)mm long; spikelets usually 3-4mm long
Poa attenuata
30.Lowest lemma (2.8-)3-4.5mm long; spikelets 3-6.5mm long
31.Green or glaucous plant, usually 25-50cm high; uppermost node about a third the way up the culm
Poa versicolor subsp. araratica
31.Very glaucous plant 10-25cm high (rarely higher); uppermost node in the lowest sixth of the culm

Lower Taxa
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