AbstractThe discovery ofSphagnum subfulvumin Western Ireland is reported and the Irish specimens are described. The habitat of the species at Errisbeg, Co. Galway, is described and compared with the occurrences in Norway. It is concluded that the ecology ofS. subfulvumat Errisbeg closely resembles its ecology in Norway where it is an intermediate/rich fen species, and in the‘mud-bottomto hummock’vegetational gradient it belongs to lawn and low hummock vegetation. The occurrence ofSphagnum subfulvumon flushed mountain slopesin West Mayo is apparently related to localised basic conditions as indicated by its association withSchoenus nigricans, Anagallis tenella, Selaginella selaginoidesandBreutelia chrysocoma. Sphagnum subfulvumis reported from raised bog in Co. Roscommon. Its occurrence in ombrotrophic vegetation is somewhat unexpected but the ombrotrophic vegetation in Western Ireland includes some species which are restricted to minerotrophic vegetation elsewhere.