Mat-forming herb with an extensive system of horizontal subterranean stems (rhizomes), thick, white, usually embedded in peat or mud, rooting at the nodes and with erect, stalked leaves and flowers from the nodes. Lateral shoots developing from axial buds within the leaf sheaths. Stems and leaves glabrous.
Leaves alternate. Petiole 1–3(5) cm long and 1 mm broad, 1–2 times as long as the blade. Stem leaves none or one attached at the lower part of the stem, with short petiole. Blades 1.1–2.2 × 0.7–2.0 cm, round to oblate in outline, palmatisect with 3 lobes with dentate apex.
Single terminal flowers on pedicels 4–6(9) cm long, 2–4 times as long as the leaves.
Flower radially symmetric, ca. 1 cm wide, with 3 ‘sepals’ and 5–6 ‘petals’. ‘Sepals’ 3–4 × 3–4 mm, shorter than ‘petals’, often deflexed, broadly ovate, outer surface green or purple and inner surface pale yellow with some purple. ‘Petals’ 4–6 × 2–3 mm, obovate, yellow. Stamens numerous (>10), ca. 2 mm, with yellow anthers and filaments. Receptacle up to 1 mm long, glabrous. Carpels 6–15, free, yellow.
The fruits are nutlets, glabrous, laterally compressed, and with long (1.0–1.2 mm), curved beaks. Head of nutlets semiglobose.
Sexual reproduction by seeds; efficient local vegetative reproduction due to extensive growth by rhizome and fragmentation. Flowers have a strong honey smell and are adapted to pollination by insects. Plants flowers regularly and produces numerous nutlets, but none of those collected in 2008 germinated (Alsos et al. 2013). They may need some special handling to get rid of inhibitors in the seed coat.
The nutlets have a floating tissue and are spread by water and probably by birds. We assume some dispersal of detached shoot fragments by water or birds.
The species of the genus Coptidium differ from those of the genus Ranunculus in several features, the most evident being the extensive system of thick, white underground stems (rhizomes) and the leaves and flowers arising mostly singly from these stems. There is nothing similar in Ranunculus. Another difference is the fragrant flowers of Coptidium (no fragrance in Ranunculus). Less visible is the corky floating tissue in the fruits of Coptidium, absent in Ranunculus.
Coptidium lapponicum is rather easily distinguished from both the other Coptidium species and the Ranunculus species in Svalbard by the 3-lobed leaves which are round to oblate in outline, and the small, pale yellow flowers on long pedicels.
Growing in wet moss tundra on slightly acidic to slightly basic substrates, usually in moist or wet moss mats.
Thermophilous. In the middle arctic tundra zone with a few localities in the northern arctic tundra zone, and in the weakly continental and transitional sections. The species is restricted to Spitsbergen. The majority of sites are found between Van Mijenfjorden and Isfjorden (Nordenskiöld Land), some on the north side of Isfjorden at Kapp Thordsen and Kapp Wijk (Dickson Land) and Bohemanneset (Oscar II Land), and a very few at Kongsfjorden (Haakon VII Land).
The general range is circumpolar in the southern arctic and the boreal zones. The Svalbard occurrences are by far the northernmost ones in the world.
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.