Identification notes
Following a detailed study of the occurrence of Leucobryum species in Britain, three species were confirmed and described in 2023. Leucobryum albidum is now known to be a locally frequent member of the British flora that is also present in Ireland and western Europe.
In the past, when only two Leucobryum species were thought to be present in Britain and Ireland, it was relatively simple to identify them (or so we thought!). L. albidum is now known to be the majority of the small, woodland plants that were previously named L. juniperoideum. This is where things begin to get a little confusing so to keep it simple, the two previous Leucobryum taxa are now aggregated and known simply as L. glaucum and L. juniperoideum agg/sensu Smith 2004. The ‘new’ species are known as L. glaucum and L. juniperoideum s.str./sensu Ottley et al 2023.
So, back to L. albidum. A Leucobryum on soil, rock or bark in a dry situation (such as on rotting tree stumps) in woodland is very likely to be this species, although small forms of L. glaucum s.str. can also grow in drier habitat. L. juniperoideum s.str. is the rarest of the three new species, and is probably restricted to very humid and sheltered places (such as wooded ravines) in the north and west. Although its appearance is variable, L. albidum has a tendency to form small, spiky-looking cushions of relatively narrow and densely packed leaves. It can however also form large spreading patches so microscopic identification is always recommended.
L. albidum typically has 6-10 rows of shortly rectangular laminal cells with squared (not sloping) end walls and a sharply defined border of 2-3 rows of narrowly elongate cells. In transverse section, the nerve generally lacks a central V-shaped groove on the dorsal side (underside).
