Solitary to mat-forming herb growing in tussocks or dense to loose stands due to branched, horizontal rhizome with short to moderately long branches, 2−8(10) cm. Base of tussocks covered by 1−3 mm broad, withered leaves and sheaths from previous years, with distinct veins, shiny, reddish brown to deep reddish purple. Culms several from each tussock, rarely single, 2−10(20) cm, erect and stiff, terete, glabrous (except for sheaths of leaves and bracts), green or reddish tinged. Leaves mainly basal; culms with 2−3 leaves, the uppermost usually above the middle of the culm.
Leaves canaliculate (especially in apex) or sometimes flat. Basal leaves 3−8(10) cm long, 1−2(3) mm broad, gradually tapering in upper half, with more or less distinct mid vein and several indistinct lateral veins, margins smooth or with very sparse, low teeth, with a few, long hairs, green, yellowish green or reddish.
Inflorescence of 1−3 (occasionally more) cymose, dense heads, each with numerous flowers (much more than 10), the central (terminal) head subsessile and usually larger than the others, 4−8 × 6−12 mm, the other heads 4−7 × 5−9 mm, dark reddish brown, on 0.5−3 cm peduncles. Peduncles usually stiff and erect but sometimes arcuate, but never branched. Inflorescence subtended by several bracts 3−6 mm long, with sheaths 1−3 mm and very short, ovate blades, reddish brown and more or less hyaline, fringed with numerous white hairs ca. 0.5 mm long. Bracteoles 0.5−1 mm, orbicular to ovate, rounded to subacute, dark reddish brown.
Flowers radially symmetric with 6 (3 + 3) tepals. Tepals subequal, 1.4−2.1 mm, lanceolate, acute, longer than fruit, reddish brown, with a very narrow hyaline margin and apex. Stamens 6. Gynoecioum of 3 carpels with 3 stigmas.
Fruit a one-roomed capsule with 3 seeds. Capsule broadly ovoid, subacute, with a very short style, shiny reddish brown. Seeds 1.0−1.2 mm, without a distinct elaiosome (see L. arcuata).
Sexual reproduction by seeds; very local vegetative reproduction by rhizomes and fragmentation. Wind pollinated. The species flowers and sets seeds profusely. Seeds germinate to 13–14 % in an experiment (Alsos et al. 2013).
The seeds have no special adaptation to dispersal. The stems are stiff, reach above the slight snow cover in early autumn, and disperse the seeds by ballistic means on the snow surface in strong winds. The only possible means of more long distance dispersal is by birds or exceptionally strong winds.
Luzula confusa is similar to L. arcuata, and these two are not clearly distinguished in the North Atlantic regions (see Comments). Luzula arcuata normally has several arcuate branches in the inflorescence, often branched anew, with loose clusters of few flowers; L. confusa normally has none or very few, stiff and erect branches in the inflorescence, never branched anew, with compact, head-shaped clusters of many flowers (much more than 10). Except for these differences, these two species are difficult to keep apart.
Dry heaths and ridges, early snowbeds, open ground. The species is common in a wide range of dry and exposed site types. Indifferent as to soil reaction (pH), but perhaps more common on circumneutral and acidic substrates, and also indifferent as to substrate structure (fine-grained or coarse).
Common in all zones and sections and one of the most common plants of Svalbard. Recorded for all major islands and for the majority of smaller ones, incl. Bjørnøya, Prins Karls Forland, Kong Karls Land, and the islands north of Nordaustlandet.
Common in the circumpolar Arctic and reaching south in boreal mountains, in Europe to S Norway.
The main reason why we treat L. arcuata and L. confusa as two separate species is how they behave outside the North Atlantic regions. In Beringia, they keep apart without any transition whatsoever (see Elven et al. 2011). In the North Atlantic regions, however, intermediate forms are common, both in Fennoscandia and in the arctic parts (see Elven et al. 2011). Whether this is a hybridization situation or something else, we do not know. The following is part of a comment by Egorova et al. in Elven et al. (2011): "The main division runs between the circumpolar Luzula confusa and the more oceanically distributed L. arcuata s. lat. Luzula confusa has long been known as sympatric with L. arcuata in the Atlantic regions but seems to be so also in the Beringian regions. The two species differ disjunctly morphologically in Beringia, whereas transitional forms occur around the North Atlantic in eastern Greenland, Iceland, Fennoscandia, Jan Mayen, and Svalbard. The two taxa should nevertheless be treated as different species."
This statement may have to be modified a little; we (R. Elven & H. Solstad) have not been able to confirm L. confusa from Iceland, whereas we in 2013 found it also in W Greenland. Both species seem to have the same two chromosome numbers, 2n = 36 and 48, and as in other species of Luzula, this does not necessarily mean a ploidy difference; it can be different degree of fragmentation of chromosomes (see Kirschner et al. 2002).
The situation in Svalbard is, at present, not very clear. Some populations from Bjørnøya and from some sites on the west coast of Spitsbergen, at least north to Krossfjorden but perhaps also farther north to Magdalenafjorden (Albert I Land), are not separable from Fennoscandian L. arcuata (from the type region) but many other populations in these coastal areas are problematic to assign. We have some tens of collections from the western parts that we are unable to assign to either L. arcuata or L. confusa. This is not unexpected; in the Scandinavian mountains, one of the species may be alone on a mountain, both present but distinct on another mountain in the vicinity, and all transistions found on a third mountain, without any explainable pattern (E. Hultén in identifications in the herbaria; R. Elven field experiences etc.). In the other parts of Svalbard, the material belongs to L. confusa and is inseparable from plants in N Greenland, arctic Canada, and arctic Russia.
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.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/
Kirschner, J. et al. 2002. Species plantarum: flora of the world. Part 6. Juncaceae: Rostkovia to Luzula. – Australian Biological Resources Study, Canberra.