Willow and alder woods occur frequently where the ground is waterlogged and within Dartmoor, the wet woodlands are often found in association with oakwoods or Rhôs pasture in valley systems.
The main tree species are grey willow, goat willow and alder, often with downy birch or ash. Otherwise, the most characteristic plants are marsh marigold, golden-leaved saxifrage, marsh violet, great tussock sedge, ferns like lady fern, scaly male fern and broad buckler fern, and bog mosses like Sphagnum palustre and S. recurvum. One notable plant that quite often occurs in Dartmoor's wet woodlands, as well as alongside rivers, is the royal fern, a large and striking species formerly much collected for ornamental purposes.
Many willow woods, or carrs, especially where the trees are old, have rich lichen communities, such as the leafy Parmelia and beard-like Usnea species. Sometimes members of the lungwort community are present, including conspicuous lichens like Lobaria pulmonaria, L. virens and Sticta species. These are all intolerant of atmospheric pollution and are used as indicators of clean air.
Typical birdlife includes redpoll, siskin, willow tit and wintering woodcock.
Small areas of wet woodland occur within many of the oakwood SSSIs that have been notified within the Dartmoor Natural Area. Sampford Spiney has fairly extensive areas of willow carr, while there is a remarkably large stand of alder at Becka Falls within the Bovey Valley SSSI. Both Sampford Spiney and Shaugh Prior Woods SSSIs have rich lungwort communities on old willow trees. Yarner Wood National Nature Reserve contains a well-developed, but small, stand of alder wood.