Identification notes
Tortula vahliana is a plant of shaded calcareous argillaceous soil, especially old quarries and chalk pits. It seems to be a colonist of disturbed substrates. Despite having plenty of potentially suitable habitat, it is quite rare and restricted in distribution. It does fruit reasonably frequently but the long cylindrical capsules often do not reach maturity, even in the absence of frost.
It sometimes occurs as scattered shoots but usually as gregarious patches. It has the bright green colour of a Tortula with papillose cells. Leaves are lingulate or spathulate and the nerve is usually excurrent in a greenish point. Sometimes, however, hair point can be longer (up to 0.5mm), becoming hyaline at the tip but remaining greenish lower down. The leaf margin is a little recurved in mid-leaf, but it lacks the strongly recurved border of forms of Tortula muralis with a greenish excurrent nerve that sometimes can be found on soil. Tortula marginata, which can be found in similar habitats, has a border of narrow cells.
The literature describes a paler marginal band of 2 cells width which is more pellucid because of fewer papillae. This is not always clear.
Two varieties have been described on the continent, based mainly on leaf and apex shape. These characters are quite variable in cultivation and we do not recognise the varieties in Britain.
Irregular nodular tubers can sometimes be found.
