Perennial of the Rubiaceae family, Galium cespitosum is a species of the mountain ranges of Western Europe, present in the Alps and the Pyrenees. It occupies rocky lawns, stabilized scree, and stony slopes at altitude, generally between 1,800 and 2,800 meters, on siliceous or mixed substrates, in full light.
It forms large, sprawling, and very dense mats, remarkably flat, barely 2 to 3 cm in height, with thin and numerous stems, covered with small whorled linear leaves of a bright and shiny green. This strictly prostrate habit, capable of covering large surfaces by conforming to the relief of the ground and stones, is one of the most striking characteristics of the species.
The flowers, tiny, with four slightly creamy white petals, are produced in very large quantities and completely cover the mat at the time of flowering, creating a snow moss effect. In its natural environment, its flowering extends from June to August depending on the altitude.
In cultivation, it requires well-drained, gravelly, and poor soil, in full sun. It is suitable for alpine rockeries where its ability to spread between stones without ever standing up makes it a ground cover of great discretion and great efficiency.