Mosses are formally classed in the taxonomic division Bryophyta
which is slightly confusing because the common term "bryophytes" also includes liverworts and hornworts. There are about 12,000 described species globally, and 763 in Britain and Ireland. For our size, we have an exceptionally diverse moss flora, probably because we are a cool, temperate and soggy set of offshore islands.
Mosses are well represented in a number of garden habitats, especially in lawns where they are not always considered welcome. The BUGS project1. identified 64 species from 61 domestic gardens in Sheffield, of which 10 were found in lawns. One species Kindbergia praelonga was present in nearly all lawns, while many others only appeared once or twice. As well as lawns, garden mosses are found in rotting wood, on garden furniture, walls and roofs, and growing on damp soil. There is much scope for keen amateurs to add a lot to our knowledge of garden moss flora, especially since the species you find will differ a lot depending on soil conditions, and how far north or west you are. In general, moss floras are most diverse in the north and west of these islands, and on acidic soils.
Types of moss
We can divide moss into two basic groups, the upright or acrocarpous mosses, and the sprawling pleurocarpous mosses. For identification, you need to look at the tiny leaves with a lens. Are they serrated like a knife around the edge or some of it; what shape are they and do they have a central nerve or not – sometimes there is one for a little way, sometimes more than one, and in some mosses these nerves extend out at the leaf end, sometimes into a whispy hair point. These can be coiled, reflexed or grey when dry. It helps identification to note where you found your sample - was it on wood, concrete, stone or soil, was it in grass or some other garden feature?
The common names of mosses are not traditional, have been invented recently, generally reflecting the mosses' appearance to help remember them. The scientific names are tongue-twisters, but great fun. Try saying the Latin names as if they are poetry – some sound really lovely.
These mosses have just a single stem with the leaves arranged up it, this may fork or have a few short branches, but basically the habit is vertical growth, as opposed to the branching and sprawling pleurocarpus mosses below. They all bear the sporophyte capsules from the tip of the stem.