Solitary herb with a tap root, a moderately densely branched caudex with more or less vertical, short branches densely covered by scaly, brown leaves, and one or several (often numerous) aerial shoots, either very short vegetative shoots with leaves crowded at ground level, or elongated reproductive shoots up to 10(15) cm. Reproductive shoots procumbent, with leaves along the entire stem up to the inflorescence. Stems and leaves weakly succulent, glabrous, glaucous or bluish green (due to bloom).

Leaves alternate. Basal leaves 2–5 cm long; petiole as long as or longer than blade, winged; blade 0.5–1.7 × 0.3–1.0 cm, broadly spathulate, gradually narrowing into the petiole, obtuse or with a minute apical tip, both surfaces with scattered, white and shiny, globular 'hairs' surrounded by a ring of small, pale cells (similar to the bases of hairs in other Boraginaceae). Stem leaves similar to basal leaves, decreasing in size upwards on stems and especially with decreasing length of petioles, the uppermost leaves nearly sessile.

Inflorescence a one-sided cyme (a monochasium) with flowers alternating on right and left side. The lowermost flowers bracteate, the upper flowers without bracts (and bracteoles). Bracts similar to stem leaves but much smaller, 0.4–0.7 × 0.2–0.4 cm. Inflorescence very short in flower stage, usually less than 1 cm, elongating somewhat in fruit stage to 1–1.5 cm. Flowers on pedicels 0.3–1 cm, increasing somewhat in length in fruit stage.

Flowers radially symmetric with calyx of 5 sepals fused for ca. 1/5 of its length, and corolla of 5 petals fused for ca. 2/3 of its length. Calyx lobes (sepals) ca. 1.5 × 1 mm in flower stage, increasing to 2–4 × 1.5–3 mm in fruit stage, broadly ovate or narrowly obcordate, acute, dark green or bluish. Corolla 3–5 × 3.5–5.5 mm, bell-shaped, sky blue. Corolla lobes (petals) ca. 1–1.5 × 1–1.5 mm, broadly triangular, obtuse or subacute. Stamens 5, attached inside the corolla tube and usually not exerted. Carpels 4, free (secondarily separated), with a common style of ca. 2 mm in a depression between the carpels.

Fruit of 4 nutlets (one from each carpel), each with one seed. Nutlets ca. 3 × 1.5 mm, acute, smooth, yellow to brown.

Sexual reproduction by seeds; no vegetative reproduction. Flowers adapted to insect pollination and probably unable to self pollinate. Fruits produced more or less regularly in Svalbard. Seeds germinate to 12 % in an experiment (Alsos et al. 2012). This comparatively low value may be due to a demand for rough handling before germination.

Nutlets have floating tissue and are adapted to dispersal by sea currents. They are able to float and germinate after an appreciable time in the sea.

There is nothing similar in Svalbard.

Sandy and gravelly seashores, occasionally also on sand or gravel some distance from the shore, e.g., on road verges in Longyearbyen where materials from the shore has been used for road construction. Usually on leaked (nutrient-poor) substrates but with some supply of nutrients from drift material (algal remains etc.) brought on the shores by high tides and wave action.

In the middle and northern arctic tundra zones and the weakly continental section. Restricted to Spitsbergen where it is found along the shores in the western parts from Van Keulenfjorden (Wedel Jarlsberg Land) north to Reinsdyrsflya on the north coast (Haakon VII Land), with main concentrations along Van Mijenfjorden, Isfjorden and Kongsfjorden.

The species is a common plant on northern seashores on all continents but the arctic race (ssp. tenella) is restricted to Svalbard, Jan Mayen, Greenland, N Canada, N Alaska and NE Asia (i.e., absent from all parts of arctic European Russia and Siberia). The connection of the Svalbard plants then seems to be to the west (Greenland).

We accept three races within the species Mertensia maritima, the two others being the amphi-Atlantic ssp. maritima that reaches the Arctic in Iceland, mainland Norway, the Murman area (Kola Peninsula), and approaches in Labrador; and the amphi-Pacific ssp. asiatica. Subspecies tenella is arctic and morphologically well characterized against ssp. maritima. Several differential characters are reported (Skarpaas et al. 2007; Elven et al. 2022). Subspecies tenella has leaves with blade broadly spathulate and apex rounded or obtuse with a short point, calyx segments ovate to narrowly obcordate, not much enlargening during fruit maturation (ca. 2 × 1 mm), and corolla 4–5 mm long with segments rounded with apex obtuse or subobtuse. Subspecies maritima has leaves with petioles relatively short, blade ovate with apex subacute to slightly acuminate, calyx segments triangular, becoming distinctly larger during fruit maturation (ca. 3.5 × 2.8 mm) and broadly cordate and acuminate, and corolla 5–6 mm long with segments triangular to cordate and acute.

Subspecies tenella differs from the North Atlantic subsp. maritima also in molecular markers. Skarpaas et al. (2007) found uniformity in isoenzymes in subsp. maritima from southernmost to northernmost Norway and differences from arctic (Svalbard) material of subsp. tenella.

Elven, R., Bjorå, C.S., Fremstad, E., Hegre, H. & Solstad, H. 2022. Norsk flora. 8. Ed. – Det Norske Samlaget, Oslo.

Skarpaas, O., Elven, R. & Nordal, I. 2007. Genetic variation and biogeography of Mertensia maritima (Boraginaceae). – Nordic Journal of Botany 24: 583–592.