A large and conspicuous moss, with pale green, sparsely branched shoots, several centimetres long, commonly 5 to 6 mm wide, that are more or less flattened in one plane and often project outwards. The leaves are about 3 mm long, and conspicuously wavy when either moist or dry. The nerve is short and double. Capsules are uncommon.

On acidic soil, wood, rocks and in turf; in deciduous woodland, conifer plantations, heathland, and amongst boulders in block scree. P. undulatum also frequently grows in blanket bogs.

Frequent and widespread in Britain.

Records for Leicestershire and Rutland are concentrated in north west Leicestershire.