Windowsill hedgehogs

Grey-cushioned Grimmia (Grimmia pulvinata) 

As the days get steadily longer (and occasionally warmer) the garden is stirring back to life. Among the brightest greens in view at the moment are the humped little mounds of an impressive variety of mosses, most as yet unidentified. The roof tiles and windowsills of our house and its various outbuildings are covered with them! We've managed to work out the ID of a few, like this Grey-cushioned Grimmia (Grimmia pulvinata), which is named for the carpet of long, dense hairs that extend from the tips of its leaves. These also give the moss its other common name – Hedgehog Grimmia. This is one of the easiest mosses to put a name to, at least when it has young spore capsules like the one above does. These green capsules curl back into the cushion on arching stems, only standing upright when they become old, dry and brown. Each capsule has a long, pointed "beak" at the tip, which helps to distinguish them from the superficially similar Grimmia orbicularis with its rounded tip. Its elliptically-shaped leaves are distinctive. It's a widespread moss, found across much of the UK, primarily in the lowlands. Elsewhere, it occurs across most of the globe, and is the most common species in its genus. It prefers sunny locations, and usually grows on stone rather than trees and shrubs. In the wild, it occurs on limestone or calcareous cliffs and boulders. However, because it can tolerate moderate levels of pollution, it's also common in urban and suburban areas, where it grows on mortar, tombstones, asbestos and concrete. So it's not an unexpected resident in our garden, but a welcome splash of greenery none-the-less.