Racomitrium

Racomitrium is a genus of mosses belonging to the family Grimmiaceae. These mosses are commonly known as beard mosses, a name derived from the often hair-like awns present on their leaf tips, which can give a beard-like appearance to the plant. They are typically found in a wide range of habitats, often in exposed and harsh environments such as rocky outcrops, alpine areas, and coastal cliffs. Many Racomitrium species are adapted to survive desiccation, meaning they can tolerate periods of dryness and then rehydrate and resume growth when moisture becomes available.

The morphology of Racomitrium species is characterized by their small to medium size, usually forming dense mats or cushions. The leaves are typically lanceolate to ovate and possess a prominent midrib. A distinctive feature is the presence of a hyaline (clear, transparent) hair-point, or awn, on the apex of many leaves, though this can vary in length and presence depending on the species and environmental conditions. Sporophytes, when present, consist of a capsule borne on a seta. The capsule is often ovate and dehisces via a distinct peristome.

Distribution of Racomitrium is global, with species found in temperate, boreal, and alpine regions across both hemispheres. Their ability to colonize nutrient-poor and exposed substrates makes them important pioneer species in certain ecosystems. Several species are particularly sensitive to air pollution and are used as bioindicators of air quality. Identification of individual Racomitrium species can be challenging and often relies on microscopic examination of leaf structure, hair-points, and sporophyte characteristics.