Identification notes

Search for this species in the winter through to mid-spring, when capsules, if they are going to develop, will be evident. Without them, Weissia sterilis is quite anonymous-looking and looks more like a Trichostomum or Didymodon more than a Weissia.

It is in Weissia subgenus Astomum, which includes species with perichaetial leaves significantly longer and wider than the stem leaves. This character can be useful in spotting potential W. sterilis plants, as the leaves at the top of the fertile stems will look different to the ones below. Even though a single shoot may have more than one capsule, they are often hidden by the perichaetial leaves and not all shoots (or even plants) have them, so careful searching of candidate material is often needed to find any. Weissia wilsonii can also have shoots with multiple capsules, but it has quite small stem leaves.

Distribution in Great Britain and Ireland

Certainly a scarce species of calcareous grassland, but easily missed. Since 2020, a significant number of new populations have been found on chalk and Jurassic limestone, suggesting it may not be quite as rare as previously thought.