Area: 9.8 hectares.
Description and Reasons for Notification:
Nymet Barton Marsh is an extensive and largely intact wetland of a type that is nationally scarce and of which there is only one other undisturbed example in Devon. Particularly extensive and well-developed stands of greater tussock-sedge Carex paniculata are present.
The site occupies a shallow valley of a tributary to the River Yeo near Bow in mid-Devon. The soils are alluvial silty clays derived from the surrounding Permian sandstones; they are waterlogged over most of the site and are moderately base-rich.
The greater tussock-sedge forms pure stands over much of the marsh and the component tussocks are particularly tall, adding to the interest of the site. Surrounding these beds are areas with high botanical diversity, characterised by plants such as meadowsweet Filipendula ulmaria, ragged robin Lychnis flos-cuculi, marsh-marigold Caltha palustris, fen bedstraw Galium uliginosum, marsh valerian Valeriana dioica, water mint Mentha aquatica and water horsetail Equisetum fluviatile. Small stands of wood club-rush Scirpus sylvaticus, a species local in Devon and an unusual one in this habitat, are present.
Parts of the site are covered by alder Alnus glutinosa and willow Salix spp. woodland, growing over beds of hemlock water-dropwortOenanthe crocata, broad buckler-fern Dryopteris dilatata and nettle Urtica dioica.
The fauna of the site is poorly known, although the nationally scarce and declining marsh fritillary butterfly Euphydryas aurinea has been recorded.