People usually notice this very small and short-lived moss in the autumn and winter, when its capsules mature and catch the eye. Without them, plants are all but invisible. It does best in pockets of bare ground where it need not compete with large or vigorous species and can be very abundant at times.
As a species, M. davallianum is relatively easy to recognise; its erect red-brown capsules have lids with a very short beak enabling quick separation from any similar looking Tortula (long beak and normally considerably larger gametophytes). Three quite distinct varieties are recognised and these, together with the closely related but much scarcer M. starckeanum, have caused much confusion in the past, mainly because of peristome differences. We now know, for example, that plants with obvious pale peristomes can be either M. davallianum var. commutatum (the rarest variety) or M. starckeanum, which always has knobbly-looking spores. Spores of all varieties of M. davallianum are regular in outline, never knobbly, although they can be variously ornamented.
- Microbryum davallianum var. davallianum – common, mature capsules look widest at the mouth, no peristome
- Microbryum davallianum var. conicum – common, mature capsules are widest below the mouth, peristome rudimentary or absent
- Microbryum davallianum var. commutatum – rare, capsules have well-developed peristome teeth
In 2022, a new key to Microbryum species in Britain and Ireland was published and can be downloaded from this page. It is a better source of information about this species than the 2010 Field Guide account, which is based on outdated taxonomy.Read the Field Guide account