Hense Moor includes some of the best remaining
examples of lowland mixed valley bog in Devon, and is typical of this habitat in South
Within an altitude range of between 150m and 210m, the valley supports a mosaic of
different habitats. These are based on a variety of different soils derived from Keuper
Marl on the valley bottoms, Greensand on the sides and Clay-with flints on the valley
tops. Peat has formed where the drainage has been most impeded. Around the valley
groundwater seeps from the Greensand and several streams arise in and flow through the
At the junction between the Greensand and Clay-with-flints moss-dominated springs
occur, Bog-mosses include Sphagnum papillosum and S.tenellum.
The site as a whole supports a diverse moss flora, some sixty species having been
recorded. Associated herbs are Bog Asphodel (Narthecium ossifragum), Bog
St.John's Wort (Hypericum elodes), Pale Butterwort (Pinguicula lusitanica),
Great Sundew (Drosera anglica) and Bog Pimpernel (Anagallis tenella).
Where wet heath grades into these boggy areas, Purple Moor-grass (Molinia caerulea)
and Cross-leaved Heath (Erica tetralix) become more abundant, together
with a variety of other species, including Fir Clubmoss (Lycopodium selago),
Round-leaved Sundew (Drosera rotundifolia), Long-leaved
Sundew (D.intermedia), Tawny Sedge (Carex hostiana), Carnation-grass
(C. panicea), Heath Spotted Orchid (Dactylorhiza maculata) and Lousewort
(Pedicularis sylvatica). On more freely drained areas the wet heath has Purple
Moor-grass and Dwarf Furze (Ulex gallii) as the codominant species.
In some areas Rushes, in particular Hard Rush (Juncus inflexus) become more
abundant. Some areas of this acid marshy grassland contain Marsh Helleborine (Epipactis
palustris), along with Star Sedge (Carex echinata) and Meadowsweet (Filipendula
ulmaria). Greater Tussock Sedge (Carex panicuata) forms well-developed
stands in some areas near the main stream.
Adding to the habitat diversity of the site are several wooded streams. Under a mixed
canopy of Alder (Alnus glutinosa), Goat Willow (Salix caprea), Birch (Betula
spp.) and Pedunculate Oak (Quercus robur), the damp and shaded ground flora
contains Golden Saxifrage (Chrysoplenium oppositifolium), Ramsons (Allium
ursinum) and Enchanter's Nightshade (Circaea lutetiana).
On the well-drained steeper valley sides and tops dry heath has developed, dominated by
Dwarf Furze. This mixes in with areas dominated by Bracken (Pteridium aquilinum)
and scrub, most of which consists of Common Gorse (Ulex europaeus) and Bramble (Rubus
fruticosus agg.). In some places on the flatter valley tops semi-improved grassland
occurs. Main sward components are Yorkshire Fog (Holcus lanatus) and Sweet
Vernal-grass (Anthoxanthum odoratum).
The site's wide variety of habitats in turn supports a rich invertebrate fauna
including of particular note the Raft Spider (Dolomedes fimbriatus). Reptiles and
amphibians are present in good numbers.