Grimmia spp.
cushion mosses
Cosmopolitan; rocky habitats worldwide
Overview
Grimmia spp. is a genus of roughly 70 to 100 species of small cushion-forming mosses in the family Grimmiaceae, found on every continent. Plants grow chiefly on rock, favouring hard, acidic, siliceous stone in exposed, sun-baked, and wind-swept places, though some species also colonise mortar and concrete. The shoots pack into dense, rounded cushions or tufts a fraction of an inch to 1 in (about 0.5 to 3 cm) high, dark green to nearly black when moist. Most species carry a long, clear, glassy hair-point at the leaf tip, and when dry these awns give the cushion a grey or hoary cast that helps shed sun and hold moisture. Spore capsules sit low among the leaves on short, often curved stalks. Like all mosses the genus has no flowers or true roots and revives from near-total drying when rain returns. G. pulvinata, the grey-cushioned grimmia, is a familiar sight on old walls, gravestones, and boulders across the Northern Hemisphere. The cushions grow slowly and are easily smothered by faster mosses on damp, shaded sites.
Native Range
The genus is cosmopolitan, native to rocky habitats on every continent including Antarctica. Species are especially varied in temperate mountains and exposed lowland outcrops of the Northern Hemisphere.Suggested Uses
Used on rock gardens, stone troughs, walls, and tile or concrete features where a slow, drought-hardy moss is wanted on hard surfaces. The genus suits crevice gardens and bonsai rockwork in sun. Cushions stabilise thin films of grit on exposed stone.How to Identify
Appearance
Size & Dimensions
Height1" - 2"
Width/Spread1" - 4"
Bloom Information
Mosses do not flower. Spore capsules mature mostly in spring and early summer, ripening among the cushion leaves and shedding spores as they dry. The cushions also spread slowly outward year-round as shoots branch and pack together.
Detailed Descriptions
Foliage Description
grey-green to blackish with white hair-pointsGrowing Conditions
Sun Requirements
Requires 4-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Plants grow on bare rock, stone, or concrete in full sun to light shade, needing sharp drainage and air movement rather than soil. They take in water and minerals from rain and dew through their leaves and shrug off long dry, hot spells by drying out and reviving when wetted. Steady damp and shade favour competing mosses, so open, exposed sites keep cushions clean. No feeding is needed. In gardens, fragments are pressed onto rough stone and kept lightly misted until they take hold. Algae and faster mosses are the main threats on over-watered surfaces.Pruning
No pruning is required. Cushions can be split and pressed onto fresh stone to start new colonies. Brushing away fallen leaves and grit keeps the surface open to light and rain.Container Growing
✓ Suitable for container growing