Run your eye across the floor of a northern conifer wood and much of the green underfoot is likely to be this one moss. Glittering wood-moss spreads in deep, springy carpets of feathery fronds, each catching the light with a faint sheen that gave it both its English and its Latin name. It ranks among the most abundant mosses on the planet, and it is one of the few that quietly keeps a record of its own past growth.
A feather with a sheen
Hylocomium splendens throws up large, arching fronds that branch two or three times over, so each spray opens out flat and finely divided like a small fern leaf. The shade is a warm yellow-green to olive, and the whole plant glistens when wet, the gloss that splendens, meaning splendid or shining, sets down in the name. Below the green the main stem runs a clear red-brown, stiff and wiry, and the fronds rise from it in tiers rather than lying in a single plane. The nearest thing to it at a glance is tamarisk moss, another thrice-branched woodland feather, but that one lies flat to the ground and stays matt, where wood-moss arches up in layered storeys and catches the light.
Reading the storeys
Here is the trick worth knowing. Each season the moss raises one arched frond; the year after, a fresh shoot springs from the back of that arch, about halfway along, rather than from its tip, and arches over in its turn. Season on season the shoots pile into a stepped staircase of tiers, which is why people across North America call it stairstep moss. Trace a single stem back through its bends and you can count the storeys much as you would the rings of a log, one to a year, and read the seasons off them: a long, generous tier marks a kind year, a short and crowded one a hard or droughty season. Hardly any other moss keeps so plain a diary of its own past, and that makes it a quiet favourite with ecologists gauging how a forest floor has fared.
A moss of the cold north
Across the boreal belt of conifer forest that rings the northern hemisphere, glittering wood-moss is one of the dominant plants of the ground layer, often sheeting unbroken for hundreds of metres beneath spruce and pine. It carries on north into the Arctic tundra and climbs above the treeline, and runs south through cooler temperate woods, heaths and old dunes, always favouring ground that is acid to neutral, cool and reliably damp. That vast carpet does real work: it insulates the soil and the permafrost beneath against summer warmth and holds water like a sponge through dry spells; and, in partnership with cyanobacteria that live among its shoots, it fixes a good share of the nitrogen feeding a northern forest. The deer and caribou wintering in those woods tramp across it to reach the lichens below, and the layer it builds shelters the same teeming microfauna found in any cushion, the small world looked at in the hidden world in a moss cushion.
Gathered and used
Few wild mosses reach the florist's bench in such quantity. Its long, even, hard-wearing fronds dry to a soft khaki and keep their shape, so it is baled up by the tonne for wreath bases, swags and the backing of Christmas arrangements, a use it shares with the cushion mosses discussed under moss in floristry. In the timber countries of the north it once chinked the gaps between cabin logs, was packed round stored apples to fend off frost, and went into the odd mattress. Most of what the trade sells is still stripped from the wild, reason enough to favour suppliers who harvest with care and to take only sparingly if you gather a little yourself.
Growing or finding it
In the garden this is a moss for a cool, shaded, leafy corner rather than a sunny bank or a centrally heated room, where its taste for damp northern air soon tells against it. Laid as whole arched wefts on firm, lime-free, humus-rich ground in light shade and watered with rainwater, it knits into a deep, walkable carpet with more spring and body than most. Under glass it asks for a cool, humid, well-ventilated case and sulks in the heat. For most of us, though, the real pleasure of it is met on a walk through an upland conifer wood or over a damp northern hillside, where you can kneel, lift a shoot, and count back down its stepped storeys to the seasons that made them.