Flicking through the moss books, you may get the impression that all of the Mnium species look pretty much like M. hornum, suggesting that you will just overlook any fancy ones until they are pointed out to you. This is generally true, in fact, but M. stellare could be the exception. It looks like a typical Mnium in many ways, a handsome acrocarp, with erect sterile shoots a few centimetres long, but is sufficiently distinctive as to catch the eye of the observant bryologist. The colour is the most noticeable feature, especially early in the year, when its lovely, fresh, ever so slightly bluish-tinged leaves make this particular M. hornum lookalike stand out. This bluish colour becomes stronger in older, dead material and can be very distinct in herbarium specimens. Closer examination clinches it: the leaves are ovate, rather than lanceolate and the leaf margins, while toothed, don’t have a border of elongated cells, unlike those of M. hornum.
The habitat is different too, as this species enjoys basic habitats whereas M. hornum prefers acid soils. However, soil pH can change rapidly with position. For example, in woodlands on chalk, covered with a layer of more acid soil as is often encountered in the Chilterns, you can be unsure of the pH situation. Be careful before jumping to conclusions on that basis alone.Read the Field Guide account