Grass Wood, Wharfedale
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Grass Wood (grid reference SD985655) is an 88 hectare woodland in Wharfedale, Yorkshire, England.
The area was notified as a Site of Special Scientific Interest in 1955. The site is also listed in the Nature Conservation Review (under the "Conistone Old Pasture and Bastow Wood" entry).
The site is managed as a nature reserve by the Yorkshire Wildlife Trust.
It is most famous as the only remaining extant native site in Britain for the Lady's-slipper Orchid Cypripedium calceolus.
Two adjacent sites Bastow Wood and Conistone Old Pasture are also recognised as SSSIs.
[edit] Site description
Grass Wood is situated on the west and south-facing slopes of a Carboniferous Limestone spur in Upper Wharfedale, to the south of Conistone Moor. Rock outcrops, scree and limestone pavement areas occur throughout the wood. The site is an ancient woodland, with Ash, Wych Elm and Sessile Oak as its principal canopy tree species. An understorey of coppiced Hazel was formerly managed by coppicing. During the 19th Century the lower slopes were interplanted with Beech and Sycamore, and in the 1960s the north-eastern part of the site was replanted with Norway Spruce, European Larch, Scots Pine and Beech. Localised variations in soil conditions mean that the site's flora contains a mixture of plants associated with well-drained and with waterlogged areas, and both calcicoles and calcifuges occur in proximity.
Areas of grassland occur, both within the wooded areas as woodland rides and as grassland banks on slopes adjacent to the wood.
[edit] Biodiversity interest
The site's designation as an SSSI is primarily due to its rich ground flora, both in the woodland and limestone grassland areas.
Among the more unusual species are Lily-of-the-valley Convallaria majalis, Stone Bramble Rubus saxatilis and Mountain Melick Melica nutans. The rides favour a meadow flora characterised by the occurrence of Great Burnet Sanguisorba officinalis, Melancholy Thistle Cirsium helenioides and Lady's-mantle Alchemilla glabra.
Associated with limestone outcrops are several locally uncommon species including Rock Whitebeam Sorbus rupicola and Angular Solomon's Seal Polygonatum odoratum. In more open situations, a limestone grassland flora has developed in which Blue Moor-grass Sesleria albicans is accompanied by herbs such as Common Rock-rose Helianthemum nummularium, Bloody crane's-bill Geranium sanguineum, Salad-burnet Sanguisorba minor and Betony Stachys officinalis.
[edit] The Lady's Slipper Orchid at Grass Wood
Lady's-slipper Orchid Cypripedium calceolus is found this site, and occurs as a native species nowhere else in Britain. The plant is found at a site near Leighton Moss in Lancashire, but is widely believed to be an introduction here. The species was formerly much more widespread in northern England, and a reintroduction project, aimed at establishing the plant at several sites across Yorkshire and County Durham, is planned.
Grass Wood contains just a single clump of Lady's-slipper plants, which flower in June.
Here, the plants grows on a fairly steep well-drained limestone grassland bank adjacent to woodland; other species growing in association with it include Bird's-eye Primrose, Herb Paris, Jacob's Ladder and Dwarf Milkwort. This bank is grazed by rabbits.
At Grass Wood, the Lady's-slipper is permanently wardened, because of the risk of damage from visitors, and the possibility that plant-collectors will attempt to remove the plants. A cage and alarmed trip-wire are placed around the plants. Visitors to the site are asked to watch the plants only from a distance. The plants are believed to be naturally pollinated by bees of the genus Andrena, but in order to maximise the likelihood of the plant continuing to survive here, hand-pollination is also carried out.
