Scrape a loose green weft off a rotting log, a shaded paving slab or the foot of a garden wall, watch it refuse to settle into any tidy cushion or neat feather, and you are very likely holding rough-stalked feather-moss. It may be the most abundant moss in lowland gardens across Britain and much of Europe, and yet hardly anyone who is not a bryologist can name it, for the plain reason that it is everywhere and looks like nothing in particular.
A moss without edges
Where many mosses announce themselves by a firm outline, this one spreads in shapeless, glossy wefts of yellow-green to rich green, brightest where the light is good and darkening in shade. The shoots branch without any pattern, sprawling and overlapping rather than combing out into the tidy herringbone of a true feather moss, so a patch has a slightly untidy, spilled look. Each leaf is broadly triangular, drawn out to a fine point and marked with a few lengthwise pleats, and a single midrib runs about halfway up it. Wet, the whole weft gleams; dry, it dulls and the shoots draw in a little, though it seldom looks truly parched, since it favours places that stay damp.
The rough stalk that names it
The feature that fixes the name hides on the fruiting stalk, and it wants a hand lens. Through much of the year, and especially in winter, the moss lifts egg-shaped, curved capsules on wiry red stalks a couple of centimetres tall. Draw a fingertip down one of those stalks and it feels distinctly rough, minutely warty under the lens, where most mosses hoist their capsules on stalks smooth as fishing line. That roughened seta is what "rough-stalked" records, and among the sprawling feather mosses of gardens it is one of the few characters you can trust to a name. The capsules are freely produced, so a thriving colony on a log or wall base is usually studded with them from autumn well into spring.
At home almost anywhere
Few mosses are so catholic about where they live. It runs over bare and disturbed soil, coats rotting logs and old stumps, climbs the shaded bases of trees and fence posts, threads through lawns, and fills the damp angle where a wall meets the ground. Unusually for a moss it takes kindly to enrichment, thriving on the nitrogen of fertile, muck-fed or disturbed ground that would sour many choosier species, which is why it turns up so readily on cultivated beds, compost heaps and the trodden edges of paths. It asks chiefly for moisture and a little shelter; give it that and it is largely indifferent to whether the surface beneath is soil, wood, brick or stone.
The strategy of a weed
What makes it so ubiquitous is speed. Rough-stalked feather-moss grows fast, colonises freshly bared ground before slower mosses arrive, and fruits heavily to cast its spores far and wide, the whole cast of a plant built to seize openings rather than to hold a hard-won spot for centuries. In the shifting, dug-over, fed and trodden ground of a garden, where stability is the exception, that opportunism pays off handsomely. It is, in the best sense, a weed among mosses: quick, tough, unfussy and forever ready to move into the next patch of bare earth or rotting wood you leave lying.
Sorting it from its neighbours
Two common mosses are its usual companions and its usual confusions. Plait moss, glossy and mat-forming too, differs in its narrow leaves that all hook the same way like a comb, and its capsule stalks are smooth; there is a full account of it in plait moss (Hypnum cupressiforme). Springy turf-moss, the spongy lawn invader, grows coarser and star-shaped, its leaves flung back at almost a right angle, and it never gleams the way this one does, as the profile of springy turf-moss makes plain. Where all three sprawl and branch, rough-stalked feather-moss is the glossier and more shapeless one, and the rough capsule stalk settles any lingering doubt. All belong to the creeping pleurocarps, the branching, mat-forming tribe set out in acrocarpous and pleurocarpous mosses.
Living with it in the garden
For the most part this is a moss to welcome, or at least to let be. It harms nothing, softens the look of a log pile or a shady wall foot, and quietly helps rotten wood on its way back to soil. Where it creeps into a lawn it is merely reporting the same damp, shaded, compacted conditions that admit any lawn moss, a matter taken up in making, or unmaking, a moss lawn. Should you actively want to grow it, you scarcely need to try: clear a patch of damp bare soil in light shade, keep it watered, and this is very often the moss that turns up first, unbidden and free.