Grimmia dry rock moss (Grimmia laevigata) is a common and widespread tuft-forming moss. It occurs on all continents except Antarctica. It is mostly restricted to the moderate climate areas of the northern and southern hemispheres. It is less common in Minnesota where it reaches the northern extent of its range. In this state it is found in open areas on rock outcrops. It grows under full sun on exposed acidic rock or on thin soil over rock.
Grimmia dry rock moss is extraordinarily drought resistant. Dried herbarium specimens that have been rehydrated after ten years have resumed photosynthetic and metabolic activity. It has adapted to a broad range of environments, yet it shows very little variability throughout its range. Bryologists suggest that a single species cannot be so adaptive, and that Grimmia laevigata must consist of a group of apparently indistinguishable but genetically distinct species.
Grimmia dry rock moss appears as a dense, hoary, dark green to dark brown tuft. The leaves have a long, thin, translucent, hair-like awn at the tip that constitutes almost half the total length of the blade. Spore-producing reproductive structures are rarely produced, and apparently are not produced anywhere in our area.