Perennial, potentially very long-lived.
Mat-forming graminoid herb with extensive, densely branched rhizome. Rhizome branch lengths 0.4–5.0(7.0) cm. Aerial shoots (3)7–10 cm, ascending to erect from rhizome, dead leaves persisting for several years and giving the stands a characteristic straw yellow colour recognizable at a distance. Culms smooth, (4)7–9(10) cm, taller than leafy shoots.
Leaves (3)7–10 cm long, shorter than culms, 1–1.5 mm broad, filiform (involute) and distinctly curved, gradually narrowing into an acute apex, scabrous only at leaf margins, with dark red or purple sheaths, yellowish green but often with withered apices.
Inflorescence and Flower
The flower in Carex is unisexual (either male or female), without perianth, and supported by a scale (the bract of the single flower). The male flower consists of 3 stamens. The female flower consists of a gynoecium of 2 or 3 fused carpels, with a single style and 2 or 3 stigmas, and with a single seed. The gynoecium is surrounded by a perigynium, a container with a narrow apical opening through which the style and stigmas emerge. The perigynia (and nuts) are either lenticular (when two carpels/stigmas) or trigonous (when three). The inflorescences are spikes, one or more per culm. If two or more spikes, all except for the uppermost are supported by more or less leaf-like bracts. Spikes may be unisexual or bisexual, and bisexual spikes may have the female flowers at base (basigynous) or at top (acrogynous). Flowers are wind pollinated and usually cross pollinated because the male flowers reach anthesis before the female flowers (protandry). Cross pollination predominates among sedges investigated in alpine Norway (Berggren & Haugset unpubl.), either due to the protandry or to genetic incompatibility. Seeds are spread inside their perigynia.
Inflorescence of only one terminal spike 0.7–1.0 × 2–3 mm, narrowly cylindrical, bisexual with female flowers at the base (basigynous). No bracts. Scales ca. 2 mm long, obtuse, reddish brown with a pale brown mid vein and more or less broad hyaline margin. Perigynia 2.5–4 × 1–2 mm, lens-shaped (lenticular with one nearly flat and one convex side), whitish-green with dark brown apex, smooth and without distinct beak. Stigmas 2.
Lenticular nut within the perigynium.
Sexual reproduction by seeds; efficient local vegetative reproduction by rhizome. Seed set is regular. Seeds germinate to only 2 % in growth chamber, but this may be due to the general difficulties of breaking dormancy in Carex (Alsos et al. 2013).
There is no special adaptation to fruit dispersal (inside perigynia) but wind and birds may affect some spread.
Carex rupestris and C. nardina are similar in habitat (both grow on exposed ridges but the former on more circumneutral substrates, the latter on more calcareous ones), but they differ in by the former having runners (mat forming) with broader leaves curved to all sides, whereas the latter is cushion forming with filiform leaves curved to the same side.
The other possibility of misidentification (and a fairly common one) is between C. rupestris and C.parallela. Both species have only one, narrow spike. Carex rupestris has bisexual spikes with female flowers at base, and leaves that are flat or canaliculated, fairly stout, and curved. Carex parallela has unisexual spikes and leaves that are thin, filiform and usually straight.
Dry heaths and open ground on wind-swept flats and ridges, partly inside Dryas heath, partly forming its own heath type, always on coarse, well-drained substrates, mainly with a basic or circumneutral soil reaction (pH).
Common in the middle and partly the northern arctic tundra zones and in the transitional to clearly continental sections. The species is nearly confined to N Spitsbergen, from Nordenskiöld Land northwards, and to a very few sites on Nordaustlandet. Farther south, there is one record from Midterhuken in Bellsund (Nathorst Land). The absence from the southern parts of Spitsbergen is probably due to prevalence of acidic substrates; the absence from the other islands may be due to climate.
The general distribution is circumpolar in the arctic and boreal zones and reaching far south in mountains in the temperate zones in North America, Europe, and Asia.
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.