Solitary herb with vertical, branched caudex, each branch ending in a short, rosette-like shoot at ground level. Flowering stems 5–15(20) cm, erect, 1–5 on each plant, simple below the inflorescence. Stems, stem leaves, and calyces with short, articulate hairs with dark violet dividing walls (making the hairs seem violet), hairs in upper parts of plant gland-tipped.
Leaves opposite, entire. Basal leaves (0.8)1.0–2.2(2.5) × (0.1)0.2–0.5 cm, in 2–3 pairs, narrowly oblanceolate to oblong, ciliate with very short hairs, dark green and often tinged with some red or purple. Stem leaves 1–3 pairs, narrower than basal leaves, the uppermost pair very reduced.
Inflorescence of a single terminal flower or more often 2–5 in a dichasial cyme, if more than one with reduced bracts. Flowers erect in both flower and fruit stage.
Flowers radially symmetric with 5 sepals and petals. Calyx fused with short (ca. 2.3 × 1.3 mm), pink to lilac lobes, at flower stage 2–2.5 times as long as broad and only slightly inflated, at fruit stage becoming slightly more inflated, ca 1.5 times as long as broad, ca 11–14 × 7–9 mm, dark greyish violet with ca. 10 distinctly marked, dark violet veins. Petals free, emerging 0.3–0.5 cm from calyx, erectopatent or patent, irregularly bifid or fringed, white. Stamens 10, enclosed or slightly protruding. Gynoecium of three fused carpels with three stigmas, with one room.
Fruit an erect capsule opening at top with 10 teeth. Seeds numerous, brown, 1.0–1.3 mm, with narrow wings ca. 0.4 mm wide.
Sexual reproduction by seeds; no vegetative reproduction. Flowering period prolonged, from late June to August. The flowers are adapted to insect pollination. The plant flowers and fruits regularly and regularly produces a high number of mature seeds. Seeds germinate to 67 % in an experiment (Alsos et al. 2013).
The seeds have narrow wings and are thus adapted to some wind dispersal along ground, but they are too large and heavy to fly high. The stems become very stiff in autumn. The combination of stiff stem, erect capsule, and apical capsule teeth assures that the dispersal only takes place above a certain wind speed (or when moved by an animal), and thus assures initial spread of seeds some distance from the mother plant.
The only plant similar to Silene involucrata in Svalbard is S. uralensis. When in flower, they differ several characters: In S. involucrata the petals emerge up to 0.5 cm from the calyx and are white and regularly notched, the flowers are erect, and the calyx is smaller and not nearly as broad as in the other species; in S. uralensis the petals emerge only a small distance from the calyx and are lilac and fringed, and the flowers are nodding (but erect after flowering), and the calyx is larger and broader, especially in the fruit stage where it becomes globular or broader than high.
Even if both species have abundant glandular hairs, S. involucrata is much more sticky than S. uralensis. Dust and dirt fragments are often attached to the stems and leaves of S. involucrata, rarely to those of S. uralensis.
Dry meadows and slopes, open patches with grass and forbs in heaths, stabilized screes, river terraces. The plant is found on both fine- and coarse-grained substrates but seems to avoid clayey soils. The substrate is usually well-drained and may periodically be quite dry. Seems to prefer substrates with a circumneutral or weakly basic soil reaction (pH) and is absent or rare both in acidic and in strongly basic areas.
Moderately thermophilous. Mainly restricted to the middle arctic tundra zone and the weakly and clearly continental sections, with a few known occurrences in the northern arctic tundra zone and in the transitional section. In Svalbard restricted to Spitsbergen and there mainly in the areas between Van Mijenfjorden and Isfjorden, around Isfjorden westwards to Colesdalen, and in the inner and middle parts of Kongsfjorden, Krossfjorden, Liefdefjorden and Wijdefjorden.
This subspecies is the arctic circumpolar part of the S. involucrata complex, present in all northern parts of Europe, Asia, North America, and Greenland. See Comments for ranges of the other subspecies.
Silene involucrata is a polymorphic species. The classical study is Bocquet (1967). After a re-evaluation of the type specimens behind the applied names, we currently recognize three subspecies at a global scale (Elven et al. 2011): the boreal and low arctic, mainly Siberian and North American ssp. involucrata (previously erroneously considered as ssp. tenella); the boreal and low arctic, N European and NW Siberian ssp. tenella (previously erroneously as Silene or Melandrium angustiflorum); and the circumpolar, high arctic ssp. furcata. Very little transitional forms are known between these subspecies, and they keep distinct even where they nearly co-occur as they do in NE Asia, Alaska, NW Canada, and Greenland. No transitions at all are known between ssp. furcata (Svalbard) and ssp. tenella (mainland Scandinavia).
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.
Bocquet, G. 1967. Physolychnidium olim Gastrolychnidium nomenclaturae fundamentum includens combinationes taxaque nova nonnulla Silenes generis. – Candollea 22: 1–38.
Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/
Müller, E., Cooper, E.J. & Alsos, I.G. 2011. Germinability of arctic plants is high in perceived optimal conditions but low in the field. – Botany 89: 337–348.