Cypripedium calceolus

Cypripedium calceolus L. (Orchidaceae) 

Lady's-slipper orchid

Status in Britain: CRITICALLY ENDANGERED. WCA Schedule 8. EC Habitats & Species Directive,

Annexes II and IV.

Status in Europe: Vulnerable.

This most celebrated plant is one of Britain's rarest orchids. Apart from plants propagated ex situ, only one clump of native origin survives in the wild. It grows on well-drained soil in herb-rich limestone grassland on a fairly steep slope adjacent to woodland. Sesleria caerulea is prominent in the sward (Walter 1993), and the wide range of associated species include Carex panicea, Epipactis atrorubens, Galium sterneri, Helianthemum nummularium, Leontodon hispidus, Linum catharticum, Polygala amarella, Primula farinosa, Sanguisorba minor and Succisa pratensis. The area is grazed by rabbits. 

C. calceolus is a perennial, flowering in June. It is believed to be pollinated by small bees of the genus Andrena (Summerhayes 1968), but the effectiveness of natural pollination is uncertain in the remaining plant.

This species was formerly more widespread, though local, in parts of northern England, growing on steep slopes of open woods of oak, ash and hazel in the limestone districts of Derbyshire, Yorkshire, Co. Durham, Westmorland and Cumberland. It disappeared from most of these areas during the last century, and has been rare in Craven for more than a hundred years, depredation of native populations for garden and herbarium specimens having been rife (Nelson 1994). A plant in semi-natural habitat in North Lancashire could have been deliberately planted, though it may be of native British origin.

The original clone is protected by a cage throughout the year, though this has not protected it against the undermining of the rhizome by small mammals. For many years, fertilisation of the few flowers which appear has been carried out by hand-pollination. English Nature's ‘recovery’ programme, in conjunction with the Royal Botanic Gardens, Kew, has been notably successful in enhancing the population. At the original site in Yorkshire, careful habitat management, together with re-establishment of plants from ex situ propagation has led to a steady increase in the size of the colony. There are now 60 shoots at the site as well as an eleven-year-old seedling which first flowered in 1993 (Lindop 1996). By 1996, plants derived from micro-propagation had been planted out at twelve additional sites as part of the on-going ‘recovery’ programme. Other plants exist in cultivation, some of which are believed to be of native stock, but some are known to have a continental origin.

This species is widely distributed through northern, central, eastern and south-east Europe, westwards to Norway and the south-west Alps, and eastwards to Sakhalin Island. It is found in several types of woodland, including those dominated by beech, larch, spruce or ash/oak, but always on moist calcareous soils, and usually on north-facing slopes, ascending to more than 2,000 metres in altitude. It is has become rare and threatened over much of its range, and is now legally protected in seven European countries.

L. Farrell