Flowering in darkness: a new species of subterranean orchid Rhizanthella (Orchidaceae; Orchidoideae; Diurideae) from Western Australia

Abstract

Few plants are so cryptic as the underground orchids, Rhizanthella Rogers (1928: 1), of Australia. Unlike the species on the eastern seaboard of Australia, the Western Australian species spend their entire life cycle, including flowering, below the soil surface (only rarely with the tips of the bracts showing), making them unique among orchids and indeed, among flowering plants generally (Brown et al. 2013). Discovery in 1928 of the first underground orchid in Western Australia was an international sensation where the plant was described as ‘a remarkable subterranean orchid’ (Wilson 1929). The new taxon described in this paper resolves the enigmatic, disjunct distribution of Rhizanthella in Western Australia, where there was thought to be a central and southern node of a single species, R. gardneri Rogers (1928: 1).