Moss Atlas mossatlas.website
Field journal
Notes from slow walks — what grows on a wall top, a bog, a shaded trunk or a pavement crack, and how to tell one from another.
One
A moss is small on purpose, so the first tool is a hand lens — 10× is enough and 20× is better. Hold the lens right against your eye and bring the plant up to the lens, rather than holding the lens out over the ground. Your hand rests against your cheek, the distance stops changing, and the image stops swimming. Everything else is patience.
Then look at the same cushion wet and dry, because most mosses are two different-looking plants. Dry, they shrivel, twist and dull down; wet, they unfold within seconds. A breath on a dry cushion or a squeeze from a small water bottle is the most useful thing you can do in the field — wall screw-moss goes from a knot of curled grey threads to a neat rosette of tongue-shaped leaves while you watch.
The stalk and the little urn on top of it are not a flower. The stalk is the seta; the urn is the capsule, and it is full of spores. Young capsules wear a calyptra — a thin hood, sometimes shaggy, left behind by the parent plant — and beneath that a lid, the operculum, which drops off when the spores are ripe. Around the mouth sits a ring of teeth that curl and uncurl with the humidity and flick spores out in dry weather.
In plain words there are two plants stacked on each other. The green leafy cushion is the moss itself, the gametophyte, and it lives for years. The stalk and capsule are a short second generation, the sporophyte, grown out of the leafy plant, fed by it, and alive only long enough to make spores. Mosses have no true roots and no plumbing to speak of: the hair-like rhizoids only anchor, and water travels across the outside of the leaves. That is why a moss can dry to a crisp and come back, and why it grows where water arrives rather than where water is stored.
Two
These eight are common, widespread and distinctive enough to name with confidence from a cushion, a wall top or a kerb edge. Filter by where you are standing.
8 of 8 shown
Wall
Grimmia pulvinata
Tight hemispherical cushions the size of a walnut on wall tops, mortar and old concrete. Every leaf ends in a long colourless hair-point, so the whole cushion looks hoary and grey from a distance. Its capsules are the giveaway: the seta curves over so far that the capsule is tucked back down into the cushion.
Wall
Tortula muralis
The moss of mortar joints, brick and kerbstones, often sharing a wall with the cushion moss above. Leaves are blunt and tongue-shaped with a fine clear hair-point, curling tightly when dry. The narrow upright capsules are the reason for the name — the teeth around the mouth are twisted into a long spiral, like a screw thread.
Woodland
Hypnum cupressiforme
Flat glossy mats on tree bases, fallen timber, fence rails and shaded rock — probably the moss you have walked past most often. The shoots are neatly flattened and all the leaves curve over to the same side, so a shoot looks plaited, or like a miniature spray of cypress. Very variable, but that one-sided curve holds.
Woodland
Thuidium tamariscinum
Bright yellow-green, stiff, and unmistakable once seen: each shoot branches three times over, so it reads as a tiny fern frond lying on the woodland floor. Likes damp shaded banks and base-rich soil. Capsules are uncommon, so identify it from the branching pattern, not from fruiting.
Bog
Polytrichum commune
Tall, dark, unbranched shoots that can reach the height of your hand, growing in loose turfs on wet heath and bog margins. Leaves spread stiffly when wet and press flat to the stem when dry. The capsule is a sharp-edged box held almost horizontally, wrapped while young in a shaggy golden hood — the hair that names it.
Bog
Sphagnum
Not one moss but a genus that builds the ground it stands on. Each shoot ends in a dense rounded head, with some branches spreading out and others hanging down the stem like a skirt. The pale dead cells in the leaves hold many times the plant’s own weight in water; squeeze a handful and it runs. Peat is what these become.
Roof
Xanthoria parietina
Leafy yellow-orange rosettes on roof tiles, wall copings, gravestones and bark near farmland — it thrives on nitrogen, so it maps where the air is enriched. Mature patches carry small orange discs, which are the fungus fruiting. A lichen is a fungus farming algae; shaded specimens lose the orange and go dull green.
Pavement
Bryum argenteum
The moss of pavement cracks, gutters, car parks and the gritty edge of a kerb, tolerant of trampling and drought. Shoots are tiny, plump and catkin-like, with leaves overlapping in neat rows. The upper leaf tips have no pigment at all, which gives each shoot a distinctly metallic, silver-white gleam.
Three
A record is worth keeping only if it lets you go back — to the place, and to what you actually saw. Six lines in a pocket book do that, and they take a minute.
A sketch beats a photograph, which is a surprising thing to claim in favour of a slower method. A photograph records what the light did; a drawing records what you decided to look at. Writing “leaves twisted when dry, hair-point about a third the length of the leaf” forces you to check both facts while the plant is in front of you. A month later that line and a rough sketch will settle an identification that forty photographs of the same cushion will not.
Four
Winter is moss season, and that is the single most useful thing to know. The canopy is off, low light reaches the ground, walls stay wet for weeks at a time, and the mosses — evergreen, fully swollen with water, and with nothing green competing for the space — are at their best while everything around them has given up. November to March is when to learn them.
Late winter into spring is when capsules ripen. Wall species carry setae by February or March, and the hoods and lids that make identification easy are present for only a few weeks before they are shed. If you want to see a calyptra still sitting on its capsule, that is the window; by June the same cushion will be carrying bare, empty urns.
Summer is the hard season, and it is easy to misread. A wall cushion in July is grey-white, brittle and apparently dead. It is not — it has dried out and stopped, which is a strategy rather than an accident, and it can hold that state for months. Do not judge a species by its summer appearance, and do not water a cushion to make it look better; it will manage without you.
Then autumn rain arrives and the whole wall turns green again within minutes of the first proper soaking. The first wet week of autumn is a good time to revisit somewhere you noted in spring, because the plants are hydrated, the capsules of the autumn-fruiting species are forming, and the difference from your summer note is the clearest lesson the year offers.
Five
A cushion the width of a coin may be a decade old, and it does not come back quickly once it is lifted. Almost everything you want from a moss can be had by kneeling down: turn a shoot with a fingernail, wet it, look at it through the lens, sketch it, and leave it attached. If you lift a stone to see the underside, put it back the way it was lying — that shaded, damp face is the whole habitat for what lives on it.
Bogs deserve more care than anything else here. The surface is alive and slow, the peat beneath it took thousands of years, and a boot print through a bog-moss lawn stays visible for seasons. Keep to boardwalks and firm paths, accept that the best patches are the ones you should not walk on, and be aware that many of these sites carry legal protection and that some of their plants are rare enough to be protected individually.
The rest is ordinary manners. Walls, churchyards, gravestones and old bridges are among the richest places for mosses and lichens and are also someone’s property or someone’s memorial — ask where asking is possible, and never scrape mortar or bark. Take the photograph, write the note, leave the wall exactly as rich as you found it.