Freiberg's screw-moss  (Tortula freibergii)

This low-growing moss is found in patches that are yellowish-green in colour, and has tiny oval-shaped leaves.

This moss is endemic to Europe, being found in Britain, France, Spain, Italy and Portugal, although it is rare throughout its range. Its sites in the UK are restricted to two near Hastings in East Sussex, scattered populations along 12km of the Bridgewater Canal near Manchester and a newly recorded occurrence along the North Yorkshire coast.

Freiberg’s screw-moss is found on acidic sandstone rocks and walls, in sheltered or fairly exposed situations.

Mosses within this branch of the family Pottiaceae get their name of 'screw-moss' from the shape of their fruiting bodies or capsules, which are formed into spirally twisted tubes. These contain the spores, the moss equivalent of seeds.

The principal threats to this species in the UK would appear to be maintenance work to the banks along the Bridgewater Canal in Manchester. The original sandstone blocks are being replaced with concrete, which are unsuitable for the moss. The removal of some of the bridges along this canal, beneath which it is known to have been found, also poses a serious threat to this species.

Freiberg's screw-moss is listed as a priority species in the UK Biodiversity Action Plan (UK BAP), and is included in English Nature's Species Recovery Programme (SRP). Although the two sites in East Sussex where this rare moss occurs have legal protection, the Manchester canal site does not. Any future development or maintenance work scheduled to be carried out should be done in the knowledge that this moss may be present. It is always possible, of course, that there are other sites where this rare species occurs that have yet to be discovered. Part of the Action Plan for this species aims to encourage bryologists to learn to identify this moss, and to survey prospective sites such as in the Wirral, Cheshire, in the hope of finding other colonies.