Atlas of North European vascular plants
Hultén & Fries 1986
554 Spiranthes romanzoffiana Cham.
This species is amphi-atlantic (Hultén, Amphi-atl., p. 208 and map 190). It has its main distribution in N. America. There are two separate population groups in Europe, viz. in SW. England and SW. Ireland and in N. Ireland and Scotland. They have been described as two separate varieties (cf. Clapham, Tutin & Warburg, Fl. Brit. Is. 1952, p. 1292f.; Hultén, I. cit.).