Identification notes

This is a fine moss and the eye-catching, beautiful, yellowish-green, pinnate shoots creeping freely through dry calcareous turf will soon become familiar in such habitats. The plant is quite robust and the 2-3mm long arrow-head shaped leaves are noticeably pleated longitudinally. The branches are numerous and remain straight when dry. So, what’s the problem? All of this sounds pretty straightforward. When growing typically, in typical habitat, you can usually be sure of a field identification, but things can get tricky – the problems arise with Homalothecium sericeum and Brachythecium glareosum.

H. sericeum is usually a smaller plant, with stems that are attached to the substrate and branches that are curled up when dry, but it can look very similar to H. lutescens when growing well and moist. In churchyards, for example, you can see a Homalothecium patch that looks like H. sericeum as it grows on the gravestone, then ‘transforms’ into H. lutescens when it spreads onto nearby grassy borders. To add to the confusion, H. lutescens can sometimes have the stems attached to calcareous rocky substrates, so be careful – if you are unsure, take some back for microscopic checking. Even then it can be a bit tricky – features like teeth at the leaf base and porosity of basal cells, mentioned in Smith’s Moss Flora of Britain and Ireland, can be a bit variable and you are often left rubbing your chin and deciding on the basis of the ‘balance of characters’, whatever that means, the last refuge of a scoundrel. If you are lucky enough to find capsules, the straight, cylindrical capsule (2-3mm.) of H. sericeum contrasts with the slightly smaller (1.5-2mm.) curved capsule of H. lutescens.

Now to B. glareosum. This looks very similar to H. lutescens in the hand, overlaps somewhat in habitat and can be really tricky. The leaf tip is drawn out into a longer, finer, sometimes twisted tip, but picking this up reliably in the field takes a lot of practice. This moss is more shade tolerant than H. lutescens, so if you are in a shaded old chalk pit or on a woodland floor on chalk, you are less likely to have the Homalothecium, but in open areas such as chalky turf and sand dunes, be careful. Microscopic checking is the policy to be adopted – here a number of features will guide you: narrower mid-leaf cells, porose basal cells, opaque alar cells, denticulate leaf margin and more rounded pseudoparaphyllia indicate the Homalothecium. Again, if your luck is in, you might have capsules – the smooth seta of B. glareosum contrasts with the papillose seta of the Homalothecium.

Distribution in Great Britain and Ireland