Graminoid forb growing in loose tussocks or dense mats, with branching both inside (intravaginal) and outside (extravaginal) leaf sheaths. Rhizome branches straw-coloured, short, 1—3 cm between aerial shoots. Aerial shoots erect or more rarely ascending from rhizome. Base of culms surrounded by a dense or loose sheath of narrow remains of withered leaves. Culms (8)10—35 cm, erect, slender (ca. 0.5 mm broad beneath panicle), glabrous, smooth or slightly scabrous.

Leaves filiform (involute) or nearly flat, green, with 7—11 veins marked as ribs on the upper surface, mid vein little different from the others, veins on upper leaf surface pubescent with short, stiff hairs, leaf margins scabrous. Basal leaves of aerial shoots 8—15 cm long, usually filiform and very narrow, 0.5—0.8 mm broad. Culm leaves 2—3, involute or more often nearly flat, 2—3 mm broad, not decreasing much in length upwards on culm, flag leaf blade 5—10(12) cm long, attached above the middle of the culm. Ligula 1.5—3 mm, acute or lacerate.

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 one mid vein (probably the floral bract), a palea with 2 mid veins (either 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 dense, cylindrical panicle, often interrupted at base. Panicle 3—5(7) cm long, very narrow (usually less than 1 cm broad) before and after flowering, up to 2 cm broad at flowering, with branches more or less erect before and after anthesis but during anthesis the branches become more patent and the panicle becomes much more open, dark violet before and early in anthesis, turning straw yellow at the end of anthesis. Panicle 1/4—1/6 of culm length with numerous nodes, having 1—3(5) branches at each of the lower nodes. Branches 8—15 mm long, densely scabrous, the longest ones with 4—7 spikelets throughout their length. Spikelets narrowly lanceolate in outline, 3—5 × 0.7—1.0 mm, 1-flowered. Bracts (glumes and lemmas) with rounded backs. Glumes 3—5 mm, subequal, as long as spikelet, narrowly lanceolate, acute, glabrous, scabrous on midvein but otherwise smooth, dark purple or violet with a narrow to broad, golden or bronze coloured hyaline margin and apex (this character disappears during anthesis when the entire panicle turns straw yellow); lower glume with mid vein and 2 very indistinct lateral veins, upper glume with 3 distinct, raised veins. Lemmas 2.5—4.5 mm, narrowly lanceolate (almost hidden by glumes), with the same coloration as the glumes and with 3 veins running into 3 teeth at apex. A stout awn, 1.5—2.0 mm, is attached below the middle of the lemma mid vein, rarely exerted from the spikelet. Callus hairs (hairs at the base of the lemma) usually ca. 1/2 as long as the lemma. Paleas about as long as lemmas or shorter, with 2 veins. Anthers 1.2—1.4 mm, well developed.

Fruit, an achene with one seed, but not observed in Svalbard material (probably overlooked).

Sexual reproduction by seed; efficient local vegetative reproduction by rhizomes into extensive, monomorphic stands, probably clones. Wind pollination. Seed production in Svalbard may be intermittent; we have rarely seen plants reaching full anthesis and never fruit maturation. Still, the significant range and the comparatively large number of stands of this species in Svalbard speak for some seed reproduction, at least in previous times.

Fruits (inside florets) have no special adaptation to dispersal but may quite easily be spread by wind and water along the ground and by birds over longer distances.

The callus hairs at the base of the lemma (see above) is a diagnostic character of the genus Calamagrostis. The other species of Calamagrostis in Svalbard, C. purpurascens, differs in very many aspects and will never be mistaken for C. neglecta. It has dense tussocks with broad leaves and bases of shoots covered by firm, dense, pale brown sheaths of leaf remains, bluish green leaves, stout culms, large, pale lilac panicles where the long awns protrude markedly from the spikelets, and grows in a very different type of sites: on dry arctic steppe heath slopes. The only other Svalbard grass remotely resembling Calamagrostis neglecta is Trisetum spicatum, also with dense, often cylindrical, dark violet panicles. However, Trisetum spicatum is always growing in tussocks, has pubescent culms (easily visible), and 2(3)-flowered spikelets with 2—3 geniculate awns long exerted from the spikelet.

On flat or gently sloping marshes or sediment plains (fine-grained substrates) with an open or partly closed vegetation cover, irrigated or inundated for parts of the season. The species is not particularly basiphilous but avoids the most acidic areas.

Rather thermophilous. The range is within the middle and northern arctic tundra zones and the weakly oceanic to weakly continental sections. Calamagrostis neglecta ssp. groenlandica is restricted to Bjørnøya (where it is rather common, 13 stations reported by Engelskjøn & Schweitzer 1970) and Spitsbergen. In Spitsbergen, the majority of its localities are concentrated to the peninsula between Isfjorden and Van Mijenfjorden, from Sassen (Sabine Land) and upper Reindalen in the east to Isfjord Radio at the entrance to Isfjorden and Lågneset at the entrance of Bellsund (Nordenskiöld Land) in the west. Elsewhere it is known from one locality in Sørkapp Land, a few localities at the south side of Bellsund (NW Wedel Jarlsberg Land), and one locality on Bohemanflya at W Isfjorden (Oscar II Land).

The global range is reported to be circumpolar (and may well be), but the somewhat intricate taxonomy of this group makes comparisons between regions problematic (see Comments).

Calamagrostis neglecta is a tetraploid species (2n = 28, x = 7). The genus Calamagrostis is probably hybridogeneous (Tzvelev pers. comm.). The lowest chromosome number known in the genus is tetraploid. There is a distinct pattern in Calamagrostis when it comes to reproductive system. All investigated N European tetraploid species are sexual, whereas all species or population groups with a higher chromosome number investigated have asexual seed production (agamospermy). There is no vivipary (bulbils) in this genus. The higher polyploids may partly have arisen within a species (autopolyploidy, as suspected for C. purpurascens and C. epigejos), and partly as hybrids between species (as shown for C. phragmitoides and suspected for C. lapponica). A huge, early cytological work has been performed on this genus, especially by A. Nygren documenting the agamospermy and some of the hybrid combinations. See Elven et al. (2011) for an extended discussion and with references to Nygren's main works.

Calamagrostis neglecta is polymorphic and has been proposed divided on several races. The uniformity seen in the Svalbard material is not the norm in other regions. In Scandinavia, two rather distinct morphological types are present: ssp. neglecta in the southern lowlands and river valleys and becoming more coastal northward, and ssp. groenlandica in the mountains and in the north except for much of the coast and the river valleys (Elven et al. 2013). Where these meet, there is a rather high frequency of stands with aborting anthers, suggesting either sterility or agamospermy. As these are long-lived plants that may persist as clones for centuries or perhaps millennia, a more detailed investigation is needed to resolve the question of sterility vs. agamospermy. Several of the characters listed above for C. neglecta ssp. groenlandica are differential towards the lowland ssp. neglecta, especially glumes which are narrowly lanceolate, acute, and with a golden or bronze coloured hyaline margin, and panicles dark violet—purple before and early in flowering. Subspecies neglecta has glumes more broadly lanceolate, subacute, shorter, and almost without hyaline margin, and panicles with greyish or yellowish green or pale lilac colours. If the differences are as sharp as indicated by Svalbard and Scandinavian material, and the intermediates pollen sterile, the rank should be reconsidered; the alternative is as two species.

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

Elven, R., Fremstad, E. & Pedersen, O. (eds.) 2013. Distribution maps of Norwegian vascular plants. IV. The eastern and northeastern element. – Akademika Publishing, Trondheim. 489 pp.

Engelskjøn, T. & Schweitzer, H.J. 1970. Studies on the flora of Bear Island (Bjørnøya). I. Vascular plants. – Astarte 3: 1–36.