Precipitation and timing of flowering in ghost orchids (Epipogium aphyllum Sw.)

Abstract

The rare, fully mycoheterotrophic Ghost Orchid, Epipogium aphyllum is only visible during its short flowering and fruiting season, which lasts for a few weeks between May and October. Due to the apparent unpredictability of its flowering, decades may pass between subsequent observations at the same locality. The factors affecting timing of flowering in this enigmatic species remain largely unexplored. In Hungary, it is an extremely rare species: between 1924 and 2014 only 25 dated observations from 15 locations are known. Hungary is located on the edge of the species’ distribution area where higher precipitation may occur only in higher regions of mountains. Hence, the spatial and temporal pattern of precipitation might limit the emergence of generative shoots. In this paper we compared rainfall patterns in relation with the Ghost Orchids’ observations to multiannual precipitation averages. The year of flowering and the month preceding flowering (but not the year before flowering and the month of flowering) were characterised by significantly more rainfall than the multi-annual average precipitation. These results suggest that the appearance of the species in Hungary is precipitation-dependent.