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 1–4 cm between shoots. Aerial shoots ascending from rhizome, at base with several prophylls (reduced leaves without or with a short blade). Culms 70–75(95) cm, erect, smooth. Base of shoots with a few withered leaves forming a loose sheath.

Leaves keeled, folded or filiform, smooth. Basal leaves 20–35 cm long, very narrow (ca. 1 mm). Culm leaves usually 2 (above the withered basal sheaths), blade 4–7 cm long, slightly broader than basal leaves (1–2 mm), flag leaf blade attached at or above middle of culm. Ligula 2–3 mm, obtuse or subacute.

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 9–12 cm long, with erect or spreading branches; panicle occupying less than 1/5 of culm length. Panicle with 10–12 nodes, with (3)4–5 branches at each of the lower nodes. Branches 30–45 mm long, moderately scabrous, the lower ones with 7–12 spikelets along more than half the branch length. Spikelets 5.5–6.5 × 1.5–2.5 mm with 3–5 flowers. Glumes and lemmas with sharp keels. Glumes 3–4 mm, about equally long, 1/2 as long as spikelet or more, lanceolate, acute, with 1–3 moderately distinct veins (lower glume often 1-veined, upper glume usually 3-veined), glabrous, scabrous on the keel in the distal half, green to violet-tinged, with a very narrow violet, bronze yellow and white hyaline margin. Lemmas 3–4 mm, lanceolate, acute, with 5 moderately distinct veins, with comparatively short wavy (curly) hairs on the proximal parts of 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. Anthers 1.4–1.8 mm, well developed with good pollen.

Fruit an achene (with one seed), not observed in Svalbard.

Reproduction by seeds, at least potentially, probably both sexual and asexual; restricted local vegetative reproduction by rhizomes. Wind pollinated. Anthers well developed, suggesting that the Svalbard plants are sexual, but observed flowering 17th September 2011 and no seed reproduction observed in Svalbard.

For comparison with other Poa species, see P. alpigena. The three most diagnostic characters of P. angustifolia compared with the other species of the P. pratensis group are the very narrow, mostly filiform basal leaves, the long, erect culms where the panicle usually constitutes less than 1/5 of culm length, and the narrow panicle with short branches.

In patches along a house in an abandoned Russian mining settlement, on moderately dry ground and probably with additional heating from the house walls.

Introduced. Found in 2011 in several garden patches, each ca. 2 × 3 m, outside a house in the mining settlement Pyramiden (Billefjorden at the inner Isfjorden, Dickson Land). The plant has probably been sown in the patches or has followed with the soil imported and used for garden plants in these patches (see Alsos et al. 2015). It sustains vegetatively, probably without any seed reproduction. It must have been there for much more than a decade and was last observed with early panicle development in August 2014.

This is a major species in the P. pratensis group in Europe and much of Siberia and has been introduced to North America. It is temperate and does not reach the Arctic as native. It is also reported as introduced in S Chukotka and Pechora (Elven et al. 2011).

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Alsos, I.G., Ware, C. & Elven, R. 2015. Past Arctic aliens have passed away, current ones may stay. – Biological Invasions 17: 3113–3123.

Elven, R., Bjorå, C.S., Fremstad, E., Hegre, H. & Solstad, H. 2022. Norsk flora. Ed. 8. Det Norske Samlaget, Oslo.

Elven, R., Murray, D.F., Razzhivin, V.Y. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/