Perennial of the Rubiaceae family, this Pyrenean population of Asperula cynanchica stands out clearly from the common form by its much denser and more compact habit, forming a tight and continuous carpet that closely embraces the rock. It occupies the high-altitude limestone lawns, rockeries, and sunny crevices of the Pyrenees, generally between 1,000 and 2,000 meters.
The stems, very branched and short, bear narrow linear leaves in tight whorls, of a bright green, which almost entirely disappear under the flowering. The flowers, tubular with four lobes, are of a delicate pinkish white, slightly more colored than those of the lowland form, and group in cymes so numerous and compact that the plant forms a true mossy cushion of flowers at the time of its full anthesis.
In its natural environment, its flowering extends from June to August depending on the altitude. In rockery cultivation, it occurs from May-June. This mountain form proves particularly generous and spectacular, significantly more floriferous than the lowland populations.
It requires well-drained, limestone soil, in full light, and easily withstands summer drought. Hardy and easy, it makes an excellent ground cover for a sunny rockery, where it can naturally associate with dianthus, as suggested by the photograph.