Perennial, moderately long-lived.
Solitary herb with a short, horizontal rhizome and a usually branched, more or less vertical caudex below and at ground level. Caudex branches short, stout (0.2–0.5 cm broad), pale greyish brown, densely covered by withered sheaths of old leaves. Leaves mostly basal. Stems 3–12(20) cm, ascending or erect, often branched in the inflorescence. The stem often branches at the top, with 1–3(4) part inflorescences. Leaves, stems and calyces pubescent with sparse (leaves) to dense (stems, calyces), articulate, more or less glandular, yellowish white hairs up to 1–1.5 mm. The plants have a slightly unpleasant smell due to glands.
Leaves alternate. Basal leaves with very short petioles, blades 3–7 × 1–2 cm, oblong to narrowly oblong in outline, densely pinnate with terminal leaflet and 6–10(12) pairs of often overlapping lateral leaflets, green. All leaflets of nearly same size and shape, 6–10 × 3–5 mm, ovate, obtuse or subacute. Stem leaves simpler with fewer pairs of leaflets, the uppermost ones as undivided bracts of branches in the inflorescence.
Inflorescence a dicotyledonous monochasial (one-sided) cyme with flowers alternating on right and left sides, with 3–5(6) flowers, ebracteate except the lowermost flower(s).
Pedicels 0.5–3 cm. Flowers radially symmetric. Calyx of 5 sepals fused in their lower 1/4–1/5, 6–9 × 3–5 mm, campanulate; calyx lobes 4–6 × 1.3–1.8 mm, oblong, obtuse or subacute, dark green. Corolla 10–20 × 10–25 mm, of 5 petals fused for about half its length, broadly funnel-formed, with corolla lobes broadly rounded. Corolla often with three colours: the lobes are sky blue, the corolla tube whitish, and often with a scarlet or purple ring between the tube and the lobes. Stamens 5, inside each corolla lobe, attached at the base of the corolla tube; filaments 5–7 mm; anthers 0.8–1 mm, broadly oblong to orbicular, violet blue, turning yellow. Gynoecium of 3 fused carpels, with 3 rooms, with style 4–7 mm and 3 stigmas.
Fruit an ovoid to globose capsule with several seeds per room.
Sexual reproduction by seeds; no vegetative reproduction. The flowers are highly adapted to insect pollination and visits by insects have been observed frequently in Svalbard. However, this species lacks the strong, honey smell of its probably closest relative, the narrowly Beringian Polemonium villosissimum (Hultén) D.F.Murray & Elven (see Murray & Elven 2011). There is no information on seed ripening or germination.
Seeds are fairly heavy and without any obvious adaptation to dispersal.
There is nothing similar to this beautiful species in Svalbard, when in flower. The pinnate leaves have some resemblance to Cardamine nymanii (Brassicaceae), but the two grow in very different site types: Polemonium in dry site types, Cardamine in very wet ones.
Heaths and meadows on favourable, usually south-facing slopes, and especially in manured places close to bird colonies. The substrate is always fairly stable, well drained, and with circumneutral to basic soil reaction (pH).
Thermophilous. Restricted to the middle arctic tundra zone and the weakly continental section. Polemonium boreale is concentrated to the central fjord districts of Spitsbergen, with some sites at Van Mijenfjorden and outer Van Keulenfjorden (Nordenskiöld Land and Nathorst Land), in Reindalen in the central parts of the peninsula between Van Mijenfjorden and Isfjorden (Nordenskiöld Land), and in the surroundings of Isfjorden on the south side from Colesbukta (Nordenskiöld Land) east to Sassen (Sabine Land), in the Gipsvika area (Bünsow Land) in the east, and on the north side from Skansebukta to Tschermakfjellet (Dickson Land) and a few places on the outer, northern side (Oscar II land).
The global range is northern amphi-Atlantic, Eurasian, amphi-Beringian and NW North American, i.e., with a large gap across much of North America and almost all of Greenland (where it only occurs as very rare in the northeastern part). The Svalbard population is therefore most probably connected to the east, to Russia, and the Greenland population is probably recruited from Svalbard or Russia. The species is very rare in mainland Europe, with one minute population group in NE Norway (see Elven et al. 2013) and a few in NW Russia, but it becomes more frequent in NE European Russia, e.g., in Novaya Zemlya.
In Svalbard and Europe, Polemonium boreale is a simple matter taxonomically but it becomes much more complicated in Siberia. For some of these complications, see Elven et al. (2011). The species was originally described from the lower reaches of the Lena River in Siberia, and the Svalbard material conforms closely to plants from this type area (R. Elven & H. Solstad observ.).
Elven, R., Fremstad, E. & Pedersen, O. (eds.) 2013. Distribution maps of Norwegian vascular plants. IV The eastern and northeastern elements. – Akademika Publishing, Trondheim.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF).
Murray, D.F. & Elven, R. 2011. Polemonium villosissimum (Polemoniaceae), an overlooked species in Alaska and Yukon Territory. – Journal of the Botanical Research Institute of Texas 5: 19 – 24.