Mat-forming graminoid herb with a horizontal, branched rhizome system. Rhizome branch lengths 1–2 cm, rather regularly with a characteristic concave bow ending in aerial shoots, usually with 1–2 post-reproductive shoots, 1–2 flowering shoots and 1–2 pre-reproductive leafy shoots in a row. Vegetative shoots (6)9–11(16) cm, ascending to erect from rhizome. Culms 10–20 cm, smooth in lower part and scabrous in the inflorescence, longer than the vegetative shoots.
Leaves 7–12(15) cm long, shorter than the culm, about 3.5–5 mm broad at the base, narrowing to an acute tip, folded or slightly revolute (M-shaped in cross section), not papillose, margins and dorsal mid vein scabrous, blade reddish brown at the base, otherwise bright green.
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 2–3(5) spikes, 1 terminal male, 1–2(4) lateral female. Male spike 10–15(17) × 3–5 mm, on a peduncle 5–15 mm, overtopping the female spikes. Female spikes 7–13 × 5–6(7) mm, on peduncles (1)5–7(10) mm, the lower peduncles usually longer than the upper ones, erect in short-grown plants, drooping in tall-grown ones. Bracts with very short, reddish-brown sheaths and a narrow acute blade, that of the lowermost spike extending into a 1–3 cm long, narrow and acute blade, upper bracts shorter. Scales of male spikes narrow, reddish to blackish brown with a lighter brown mid vein and a white hyaline tip. Scales of female spikes triangular, shiny dark brown with a narrow, white hyaline margin and tip. Perigynia 2.2–4.0 × 1.1–2.3 mm, lenticular, shiny blackish brown, narrowing towards a smooth, bifid beak 0.1 mm long. Stigmas 2(3).
Lenticular nut within the perigynium.
Sexual reproduction by seeds; local vegetative reproduction by rhizome. Apparently ripe seeds did not germinate in growth chamber, but this may be due to the general difficulties of breaking dormancy in Carex (Alsos et al. 2013).
Fruits (inside perigynia) are spread by water and probably by birds.
Carex saxatilis is rather easily recognised on its large, dark, shiny and (mostly) erect female spikes. The only other Carex in Svalbard with inflorescences of similar size is C. fuliginosa ssp. misandra, which grows in cushions with spreading, curved leaves, has nodding to pendulous spikes, and a bisexual terminal spike.
Rich, more or less sloping mires in more or less calcareous sites, on firm peat, never in very wet mires.
Thermophilous. Mainly restricted to the middle arctic tundra zone and the weakly and clearly continental sections, but a few populations in the northern arctic tundra zone and transitional section. The species is restricted to N Spitsbergen, from N Nordenskiøld Land and northwards. The absence from the southern parts of Spitsbergen is probably due to acidic substrates.
The general range of Carex saxatilis is circumpolar in the arctic and boreal zones and extending south to temperate mountains in W North America and E Asia (but not Europe). The range of its two subspecies has been uncertain (see, e.g., Hultén 1968, Egorova 1999) but is now more or less clarified by morphological and molecular evidence (Elven et al. in prep.). Pedersen et al. (2016) did not find differences in microsatellite markers between the N Norwegian plants assumes as ssp. laxa and other Scandinavian plants, and Elven et al. (in prep.) confirmed this also for Svalbard and the majority of Greenland plants. Subspecies laxa, which has previously been assumed to be the race present in Svalbard, is distributed from a smaller area in W Greenland westwards through North America to Siberia, but not present in Europe including Svalbard. The race in Svalbard is subsp. saxatilis, as elsewhere in Europe and NE Greenland.
Carex saxatilis is a very polymorphic and complex species. The type of the species is from “Europe” (unspecified, probably Scandinavia) and ssp. saxatilis is the European plant. Whereas such European plants are small-grown, with short peduncles of the female spikes (and thereby nearly erect spikes), and grow in rich mires, the plants of boreal parts of Asia and North America are much more tall-grown (often more than 1 m) and with long pedunculate nodding or pendulous female spikes. They are recognized as ssp. laxa based on a type from “fl. Tomba” in Siberia. These plants also have much broader leaves and larger perigynia and more often grow in swamps. These differences become less pronounced in arctic plants, but even here the difference in the pedunculate female spikes holds. American authors have been very reluctant to accept races (e.g., Ford et al. 1991; Ford & Ball 1992; Reznicek & Ford 2002), whereas European and Russian authors usually have accepted the two races (see also comments in Elven et al. 2011).We still do so, but now their ranges have been decided.
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.
Egorova, T.V. 1999. The sedges (Carex L.) of Russia and adjacent states. – St.-Petersburg State Chemical–Pharmaceutical Academy, St.-Petersburg, and Missouri Bot. Gard. Press, St. Louis.
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., Pedersen, A.T.M., Bødker, K.H. & Bjorå, C.S. In prep. Carex saxatilis s.lat. (Cyperaceae) in Greenland – not one, but three species.
Ford, B.A. & Ball, P.W. 1992. The taxonomy of the circumpolar short-beaked taxa of Carex sect. Vesicariae (Cyperaceae). – Systematic Botany 17: 620–639.
Ford, B.A., Ball, P.W. & Ritland, K. 1991. Allozyme diversity and genetic relationships among North American members of the short-beaked taxa of Carex sect. Vesicariae (Cyperaceae). – Systematic Botany 16: 116–131.
Hultén, E. 1968. Flora of Alaska and neighboring territories. A manual of the vascular plants. – Stanford Univ. Press, Stanford.
Pedersen, A.T.M., Nowar, M.D., Brysting, A.K., Elven, R. & Bjorå, C.S. 2016. Hybrid origin of Carex rostrata var. borealis and C. stenolepis, two problematic taxa in Carex section Vesicariae (Cyperaceae). PlosOne https:/doi.org/10.1371/journal.pone.0165430
Reznicek, A.A. & Ford, B.A. 2002. Carex Linnaeus sect. Vesicariae (Heuffel) J. Carey. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico. 23. Magnoliophyta: Commelinidae (in part): Cyperaceae: 501–511.