Poa pratensis s. lat. is currently in Norway considered a group of five closely related species, all present in Svalbard: P. alpigena and P. colpodea as native, P. angustifolia, P. humilis, and P. pratensis (s. str.) as introduced. See Elven et al. (2022).
Mat-forming graminoid herb growing in dense stands due to horizontal, branched rhizomes, typically with rhizome branches of (3)4–6 cm between aerial shoots. Aerial shoots ascending from rhizome, at base with several prophylls (reduced leaves without or with a short blade). Culms 30–60(75) cm, erect, smooth. Base of shoots with a few withered leaves forming a loose sheath. Leaves and culms glabrous.
Leaves keeled, flat (culm) or folded (basal), smooth. Basal leaves 12–20 cm long, narrow, 1–2 mm broad, tapering at the apex. Culm leaves usually 2–3, blade 5–11 cm long, much broader than basal leaves, 3–5 mm. Flag leaf blade attached at or above middle of culm. Ligula 2.5–3.5 mm, obtuse or subacute.
INFLORESCENCE AND FLOWER
The units of the inflorescence of Poaceae are the spikelets, nearly always numerous in a panicle or spike-like inflorescence. Spikelets are composed of 2 glumes (bracts for the spikelet) and one or more flowers (the term used below) or rather floral units often named ‘florets’ because we do not know what is the exact flower. A flower or floret is composed of a lemma with 1 mid vein (probably the floral bract), a palea with 2 mid veins (either 2 fused bracteoles or perhaps 2 fused perianth leaves), 3 small organs called ‘lodiculae’ and essential in the opening of the flower at anthesis (possibly transformed perianth leaves or transformed stamens), 3 stamens (mostly), and a gynoecium of 2 fused carpels with 2 feathery stigmas and one seed.
Inflorescence a narrowly elongate pyramidal panicle 10–15 cm long, with erect to spreading branches; panicle occupying 1/4–1/5 of culm length. Panicle with 8–11 nodes with (3)4–5 branches at each of the lower nodes. Branches 40–70(80) mm long, very sparsely scabrous, the lower ones with 4–10 spikelets (occasionally even more) along more than half the branch. Spikelets 6–8 × 2–2.5 mm, with 4(5) flowers. Bracts (glumes and lemmas) with sharp keels. Glumes 4–5 mm, about equally long, 1/2 as long as spikelet or more, lanceolate, acute, with 1–3 distinctly raised (sharp) veins, glabrous, scabrous on the keel in distal parts, green to tinged violet with a very narrow violet and white hyaline margin. Lemmas 3.5–4.5 mm, lanceolate, acute, with 5 distinctly raised (sharp) veins, with comparatively short wavy (curly) hairs on the proximal parts veins and keel but glabrous between the veins, with a distinct tuft of cottony hairs at the base of the lemma, green or tinged violet with a narrow hyaline margin variegated in violet, bronze yellow and white. Paleas shorter than lemmas, with pubescent veins.
Fruit an achene (with one seed). Fruits probably not produced in Svalbard.
Reproduction by seeds, probably both sexual and asexual (agamospermy), but no seed reproduction recorded in Svalbard; efficient local vegetative reproduction or at least sustenance by vegetative growth (short rhizomes). The lack of seed reproduction in Svalbard is due to late flowering.
Fruits (within florets) are dispersed, if ever realized, by wind or animals.
For comparison with other species of Poa, see P. alpigena. The three best diagnostic characters of P. pratensis compared with the other species of the P. pratensis group are the much longer and broader leaves (P. humilis also has broad leaves but they are much shorter than in P. pratensis), the long, erect culms with an elongate to pyramidal panicle (P. alpigena and P. angustifolia usually have a narrow panicle, P. humilis a broadly pyramidal one), and the very numerous spikelets per panicle (often much more than 50). It has the sharply raised, very distinct veins with sparse hairs in common with P. angustifolia, a character distinguishing these two from P. alpigena and P. humilis (the latter two have less distinct but much more pubescent veins).
On disturbed and often fertilized ground in settlements, on refuse tips, and by cabins.
Introduced. Poa pratensis has been collected repeatedly in many of the current and abandoned settlements and also by several huts on Spitsbergen, from Calypsobyen in Recherchefjorden (in 1939, Wedel Jarlsberg Land) north to Ny-London on Blomstrandøya (in 1932, Haakon VII Land). At 6 or perhaps 7 sites it has been found over a long time span or recently and may be persistent: Longyearbyen (1915–2013), Hiorthhamn (a long abandoned mining settlement at Adventfjorden, 1928–2013), Ny-Ålesund (1928–1975, probably not looked for later), Hotellneset near Longyearbyen (1928–2013), Barentsburg (2008), Pyramiden (2008–2013), and at Tunheim on Bjørnøya (1957–1984, not looked for afterwards). Emil Hadač, when travelling through central parts of Spitsbergen in 1939, collected it in six sites in that single season.
This is a major species in the P. pratensis group in Europe, West Asia and probably also North America (Soreng 2007). It is mainly temperate and probably absent as native from the Arctic.
This is one of the most important fodder grasses in the northern temperate zones, only competing with Timothy Phleum pratense, English ryegrass Lolium perenne and Meadow fescue Lolium pratensis. Its presence as rather frequent in Svalbard from the 1920s into the 1960s was probably due to the extended husbandry at that time (without regular ship transport in winter or air transport), based on imported fodder for cows, horses, pigs etc. With more regular and dependable import of foodstuff to Svalbard from the 1970s onwards, the animals largely disappeared from the Norwegian settlements (except for a current hobby horse farm on Hotellneset) but not from the Russian ones where they still keep pigs in Barentsburg. The majority of the perennial plants introduced with the fodder were able to sustain for some years but eventually died away. However, P. pratensis seems to have sustained or has been re-introduced.
The majority of the older material was not originally recognized as P. pratensis s. str. but rather as P. alpigena var./ssp. domestica (Laest.). This is due to what we suspect is a mistake in how the two species were distinguished from each other. The key character applied by Hylander (1953), following a tradition from the major Nordic grass specialists in the 1920s and 1930s and continued by, e.g., Elven et al. (2022), is in the number of veins on the glumes. The lower glume should have only one vein and the upper three veins in P. pratensis and P. angustifolia, both glumes should have three veins in P. alpigena and P. humilis. Applying this character alone, a fairly arbitrary division is reached. The Svalbard plants we now assign to P. pratensis are inseparable from the common fodder grass in European managed meadows.
Edmondson, J.R. 1980. Poa L. – In: Tutin, T.G. et al. (eds.), Flora Europaea. 5. Alismataceae to Orchidaceae (Monocotyledones): 159–167.
Elven, R., Bjorå, C.S., Fremstad, E., Hegre, H. & Solstad, H. 2022. Norsk flora. Ed. 8. Det Norske Samlaget, Oslo.
Hylander, N. 1953. Nordisk Kärlväxtflora, I. – Almqvist & Wiksell, Stockholm.
Lid, J. & Lid, D.T. 2005. Norsk Flora. Ed. 7 by R. Elven. – Det Norske Samlaget, Oslo.
Soreng, R.J. 2007. Poa L. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico 24. Magnoliophyta: Commelinidae (in part): Poaceae, part 1: 486–601.