Silene acaulis

Silene acaulis
Silene acaulis in Svalbard
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Caryophyllales
Family:	Caryophyllaceae
Genus:	Silene
Species:	S. acaulis
Binomial name
Silene acaulis (L.) Jacq.

Silene acaulis, known as moss campion or cushion pink, is a small mountain-dwelling wildflower that is common all over the high arctic and tundra in the higher mountains of Eurasia and North America, (south to the Alps, Carpathians, southern Siberia, Pyrenees, British Isles, Faroe Islands, Rocky Mountains). It is an evergreen perennial.

It is also called the compass plant, since the flowers appear first on the south side of the cushion. (Various other plants also have this name.)

Moss campion is a low, ground-hugging plant. It may seem densely matted and moss-like. The dense cushions are up to a foot or more in diameter. The plants are usually about 2" tall but may be as high as 6". The bright green leaves are narrow, arising from the base of the plant. The dead leaves from the previous season persist for years, and pink flowers are borne singly on short stalks that may be up to 1" long, but are usually much shorter. It usually has pink flowers, though very rarely they may be white. The flowers are solitary and star-shaped. They are between 6 and 12 mm wide, with hermaphrodite flowers being larger than the female ones. Female flowers produce better quality seeds than hermaphrodites and male flowers produce better quality pollen than hermaphrodites. The cushions can change the gender of their flowers between years. Gender frequencies change with altitude, the frequency of female flowers increasing with higher elevation. They usually appear in June through August. The flowers are held by a calyx which is rather firm and thick. The flowers are female, male or hermaphrodites.

The sepals are joined together into a tube that conceals the bases of the petals, which are entire. The 10 stamens and 3 styles extend well beyond the throat of the flower. This genus, circumpolar in its distribution, is closely related to carnations. The stems and leaves are very sticky and viscid, which may discourage ants and beetles from climbing on the plant. The variety exscapa has shorter flowering stems. The other variety subacaulescens, from Wyoming and Colorado, has pale pink flowers all summer.

Alpine fellfield, on windswept rocky ridges and summits above treeline. It grows mainly in dry, gravelly localities, but also in damper places. With the cushions it produces its own, warmer climate with higher temperatures inside, when the sun shines.

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Wikipedia