Of the estimated 191 species (Baumann & Künkele 1982) currently accepted for Europe, The Middle East and North Africa, only 53 are native to the British Isles. One of these, Spiranthes aestivalis (Poir.) L.C. Rich., is generally considered to be extinct.

Many Continental species, e.g. Epipactis muelleri Godfery, Limodorum abortivum (L.) Sw., Orchis coriophora L. and Serapias cordigera L., were prevented from ever reaching our shores by the formation of the English Channel around seven thousand years ago. Others, such as most Ophrys species, e.g. O. scolopax Cav. and Serapias species, e.g. S. lingua L., require a warmer, drier climate and only extend as far as south-west and south-central France. Although the majority of British orchids may be seen in greater numbers across the Channel, it is a mistake to assume that our native orchid flora is merely a poor representation of Continental Europe. Several species, particularly those of chalk grassland, are as widespread in Britain as elsewhere. Among these may be included Anacamptis pyramidalis (L.) L.C. Rich., Dactylorhiza fuchsii (Druce) Soó and D. maculata (L.) Soó, Epipactis helleborine (L.) Crantz, Gymnadenia conopsea (L.) R.Br., Orchis mascula L. and Platanthera chlorantha (Custer) Reichb.

A few species have their main European distribution in the British Isles, e.g. Epipactis phyllanthes G.E. Sm., a variable plant, some forms of which have cleistogamous flowers. On the Continent it is only found in western France and Denmark. Spiranthes romanzoffiana Cham. is an example of a North American species which, in Europe, is confined to Ireland, Western Scotland and Devon.