This species, although quite common in many upland areas, closely resembles Polytrichum formosum and can be mistaken for it. Knowing the habitat of P. alpinum helps – it often prefers drier, more exposed places than P. formosum so look for it on wall tops and in crevices of dry rock faces and boulders. Its stems are often – but not always – a little shorter and more branched than that species and they have slightly more curved back leaves, a feature that makes it look subtly different in the field.
Back at base, section a leaf to confirm your identification. As the photos below show very clearly, the apical cells of the lamellae are larger than those below and papillose, making them look rather strawberry-like.Read the Field Guide account