Mat-forming herb with short, vertical caudex and procumbent and rooting branches at or just below soil surface. Caudex and branches end in leaf rosettes at ground level. Each rosette potentially with several lateral, procumbent or ascending flowering stems. Flowering stems up to 25 cm long but usually much shorter.
Leaves alternate, mostly basal, with petioles up to 7 cm, much longer than blade (1.5)1.7–2.5(2.7) × (1.8)2–2.5(3) cm, and blades with 3–5 sessile leaflets. Hairs on petiole sparse, 0.5–1.5 mm long, smooth, straight or slightly curly. Both leaf surfaces green. Lower leaf surface and veins sparsely pubescent with hairs similar to petiole and sparse, subsessile yellow glands. Upper leaf surface very sparsely pubescent. Leaflets oblong or obovate in outline, non-overlapping, crenate or shallowly lobed with 3–5 pairs of obtuse teeth or lobes in the distal 2/3 of the leaflet, lateral leaflets (0.9)1.2–1.7(2.0) × (0.5)0.8–1.4(1.6) cm, terminal leaflet (1.2)1.4–2.0(2.3) × (0.6)1.0–1.3(1.5) cm. Stem leaves reduced, with 2–3 small leaflets.
Inflorescence a cyme with 7–15 bracteate flowers. Bracts simple or dentate.
Pedicels 2.5–5 cm. Flowers radially symmetric with 5 free epicalyx bractlets, sepals, and petals. Hypanthium, epicalyx bractlets and sepals with sparse, long, white hairs and more abundant, yellowish glands. Epicalyx bractlets, 2.5–3.2 × 1.3-1.7 mm, ovate or oblong, narrower than sepals. Sepals 4–5.5 × 3–4 mm, triangular or narrowly triangular. Petals 6–8 × 4–6 mm, ca 1.5 times as long as sepals, obcordate, distinctly emarginated, bright yellow with an orange spot at base. Stamens numerous. Carpels numerous, free. Styles apical, 1–1.5 mm, tubular and very slender, without basal papillae.
Fruit a nutlet, up to 20–30 or more from each flower.
Reproduction by seeds, probably both sexual and asexual (agamospermy); local vegetative reproduction by rooting branches within a few centimetres from the central rosette. The flowers are adapted to insect pollination. The plant is facultatively agamospermic, that is, able to form seed both sexually and asexually (without fertilization of the egg cell; Nyléhn 2002). However, asexual seed development depends upon pollination for fertilization and development of the endosperm (the nutrient tissue for ovule development), a phenomenon named pseudogamy (Müntzing 1928; Gentscheff & Gustafsson 1940). Such endosperm fertilization is often more efficient with pollen from a relative than from the same species (Asker & Jerling 1992; Nyléhn 2002). This makes for interesting possibilities in plants with a potential for hybridization (see Elven et al. 2011). Potentilla crantzii flowers regularly and production of mature fruits is regular in Svalbard (R. Elven observ.; herbarium specimens).
There is no special adaptation to dispersal.
Potentilla crantzii and P. hyparctica differ from the other Potentilla in Svalbard by having leaves green on both surfaces; the others have leaves white on the lower surface due to dense pubescence, sometimes also on the upper surface (P. insularis, P. lyngei, P. pulchella). The main differences between P. crantzii and P. hyparctica are: In P. crantzii flowering stems distinctly lateral and procumbent or ascending, leaves with 3–5 leaflets, flowering stems nearly always with several flowers, and inflorescences with sparse and yellowish glands; in P. hyparctica flowering stems subterminal and erect, leaves always with only 3 leaflets,flowering stems one-flowered, and inflorescences with abundant and reddish glands.
Herb slopes, meadows at base of cliffs, sheltered depressions with dense vegetation cover; nearly always in sites with good snow protection, a deep active layer, and stable substrate; a few times found in the peripheral parts of bird cliff meadows. The substrate is always well-drained, mainly sand to gravel, but not very dry. Potentilla crantzii is not very specific as to soil reaction (pH) but is absent from both the most basic and the most acidic areas.
Thermophilous. Mainly confined to the middle arctic tundra zone but transgressing into the northern arctic in the Hornsund area and in N Spitsbergen. Mainly found in the transitional and weakly continental sections, rare in the weakly oceanic one and very rare in the clearly continental one. Restricted to Spitsbergen but there found with localities scattered from Hornsund north to Wijdefjorden and the north coast.
This is an amphi-Atlantic species, widespread throughout Europe and into W Siberia, west of the Atlantic in Iceland, Greenland, and E Canada.
Potentilla crantzii belongs, together with P. hyparctica, to section Aureae, whereas the other Svalbard species of Potentilla belong to sections Niveae and Pensylvanicae and assumed (but not proven) hybrid species between these two latter sections. Some specialists in Potentilla (e.g., J. Soják and B.A. Yurtsev) have claimed that what we here consider as P. crantzii in Svalbard includes two species and their hybrid: P. crantzii with regularly five leaflets per leaf, P. gelida C.A.Mey. with regularly three leaflets, and P. scandica Soják with 3–5 leaflets (described with a type from the Jotunheimen mountains in S–C Norway). As for mainland Scandinavia and Svalbard, the variation in number of leaflets is found within regions, within populations, and sometimes within individuals (Elven et al. 2011). There is no molecular support for two or more species (Nyléhn 2002); Scandinavian and Svalbard plants belong within P. crantzii as do the type specimen of P. scandica. Kurtto et al. (2004) synonymized P. gelida with P. crantzii, a conclusion we do not concur with. Potentilla gelida is probably acceptable as a species but is restricted to the Caucasus and easternmost Russia and Siberia and not relevant for our regions.
Potentilla protea Soják has been described as a hybrid species from P. crantzii × P. hyparctica, based on a type from North Greenland. Soják and Yurtsev have reported this hybrid species from Svalbard but we have not yet been able to confirm it based on identification of Svalbard specimens. The Svalbard material we have seen annotated as P. protea by Soják, we rather interpret as P. hyparctica. We have, however, seen Greenland material combining the features of the two species.
Asker, S. & Jerling, L. 1992. Apomixis in plants. – CRC Press, Boca Raton.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/
Kurtto, A., Lampinen, R. & Junikka, L. 2004. Atlas florae europaeae. Distribution of vascular plants in Europe. 14. Rosaceae (Spiraea to Fragaria, excl. Rubus). – The Committee for Mapping the Flora of Europe and Societas Biologica Fennica Vanamo, Helsinki.
Müntzing, A. 1928. Pseudogamie in der Gattung Potentilla. – Hereditas (Lund) 11: 267–283.
Nyléhn, J. 2002. Predominant cross pollination in an alpine population of the facultative apomict, Potentilla crantzii (Crantz) G.Beck ex Fritsch, Rosaceae. – In: Nyléhn's Dr. scient. Thesis, Univ. Oslo, Oslo.