Mat-forming graminoid forb growing in often extensive stands due to horizontal rhizome with whitish branches, typically with rhizome branch lengths of (3)5−8(10) cm between aerial shoots. Aerial shoots ascending from rhizome, at base without or sometimes with a very few prophylls (reduced leaves without or with a short blade). Base of culms surrounded by a narrow sheath of withered leaves. Culms (10)15−25(30) cm, erect, slender (0.7−1.2 mm broad above the flag leaf, ca. 1.5 mm broad below the flag leaf), smooth. Culms and leaves often strongly tinged with purple or violet.

Leaves flat or folded (convolute), with a marked mid vein and a weak keel, smooth, with numerous lateral veins slightly raised on the upper surface. Basal leaves 5−10(15) cm long, narrow (0.8−1.5 mm), tapering near apex. Culm leaves 2−3, similar to basal leaves but broader (1.5−2.5 mm), flag leaf blade 3−5 cm long, attached at or below the middle of well-developed culms. Ligula short, 1(2) mm, truncate, fringed.

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 pyramidal panicle when fully developed, 4−10(12) cm long, with spreading, patent or down-pointing, straight branches. Panicle occupying 1/3−1/4 of culm length, with 5−8 nodes, the lowermost nodes at about the same distance from each other. Branches (1)2−4(5) at each of lower nodes, smooth, the longest 20−50 mm, each with 1−5 spikelets in their distal part. Spikelets 5−8 × 1.5−2.5 mm, usually with 1−4 flowers (but only 1−2 functional). Bracts (glumes and lemmas) with rounded backs, a distinct mid vein and 2 indistinct lateral veins. Both glumes of nearly the same length, 5−8 mm, extending to the top of the spikelets and usually beyond the lemmas. Glumes lanceolate to narrowly lanceolate, acuminate and with an extended, cusp-like apex turning inwards in the spikelet, glabrous, smooth and shiny, violet or purple in the lower and central parts but with a narrow or more often broad, golden yellow, hyaline margin and apical part. The mid vein, which often extends into the cusp, is black or nearly black, and contrasts with both the violet and golden parts of the glumes. The coloration of the glumes (and lemmas if visible) and their mid vein are good characters for recognition of the species. Lemmas 4−6 mm, narrowly lanceolate, acute or obtuse (and often fringed), with the same coloration (margin violet and hyaline golden, narrow or broad) and mid vein as glumes, sparsely to moderately pilose. Palea with broad hyaline margin, smooth or slightly scabrous on keels, shorter than lemmas. Anthers violet, narrow, 2−3(3.5) mm, usually well developed.

Fruit an achene (with one seed).

Sexual reproduction by seeds; efficient local vegetative reproduction by extensive clonal growth, forming large stands and resulting in (physiologically) new individuals when the mat is fragmented by frost soil movement (cryoturbation), erosion, flooding or other accidents. Wind pollination; probably an outcrossing species. Seeds germinate to 36 % in an experiment (Alsos et al. 2013).

Fruits are spread by water and birds. We also assume that birds may spread shoot fragments over shorter distances.

Dupontia fisheri s. lat. is distinguished from Arctophila by much narrower leaves, those of vegetative shoots not conspicuously distichous (with leaves in two dense rows), in glumes and lemmas much more elongated into acute, acuminate or fringed apices, and in glumes as long as the spikelet and longer than the lemmas. For differences towards Arctodupontia scleroclada, see that species.

The tetraploid ('psilosantha') morph of Dupontia fisheri is distinguished from the octoploid morph ('fisheri') by its culm becoming more slender beneath the panicle, a broadly pyramidal panicle with long, patent or even retrorse branches, and by growing in permanently very wet or submerged marshes.

The tetraploid ('psilosantha') morph of Dupontia fisheri is a typical inhabitant of very wet marshes, often with floating leaves together with Arctophila fulva, and usually with its bases in water or in a soaked moss carpet. It is a major constituent of the brackish marsh vegetation along the shores of Svalbard. It is indifferent as to soil reaction (pH) but always grows in places with abundant soil water from rivers, snow or melting permafrost, or tidal inundation on seashores.

Occurs in the middle and northern arctic tundra zones and in the weakly oceanic to clearly continental sections, perhaps transgressing into the clearly continental section. This morph is the only one on Bjørnøya and is common there (Engelskjøn & Schweitzer 1970). It is recorded as frequent on Spitsbergen from Sørkapp Land in the south to Liefdefjorden and Sorgfjorden in the north and from Prins Karls Forland. It is not recorded from Nordaustlandet but from a few sites on Edgeøya and Kong Karls Land. It seems to be less hardy than the octoploid morph ('fisheri') in Svalbard, as noted already by Scholander (1934). This applies also outside Svalbard; the tetraploid morph (‘psilosantha’) being more southern than the octoploid morph (‘fisheri’) throughout their distribution range.

Both morphs of D. fisheri are rather common in most arctic regions but rare in Greenland (Bay 1992; Elven et al. 2011). They are also absent from the N Russian regions west of the White Sea and from NW Europe except for Svalbard. The connection is therefore probably to the east, to NE European Russia.

For general comments to the genus Dupontia and its subdivision, see D. fisheri octoploid morph, Brysting et al. (2003, 2004), and Elven et al. (2011).

Alsos, I.G., Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.

Bay, C. 1992. A phytogeographical study of the vascular plants of northern Greenland – north of 74 northern latitude. – Meddelelser om Grønland, Bioscience 36. 102 pp.

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

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

Scholander, P.F. 1934. Vascular plants from northern Svalbard with remarks on the vegetation in North-East Land. – Skrifter om Svalbard og Ishavet 62. 155 pp.