The shifting ecology and distribution of one of Britain’s rarest plants: Orobanche picridis (Orobanchaceae)

Abstract

Orobanche picridis F.W. Schultz (Picris Broomrape) is perhaps the rarest and certainly the most misidentified British broomrape. This rare plant was perceived to have a distinct ecology in Britain where, until recently, extant populations were virtually restricted to high, chalk sea cliffs. Though widely recorded across Southern England, most records have proven to be erroneous due to confusion with the similar, often co-occurring, common broomrape (O. minor). The preference of O. picridis for steep and inaccessible chalky ledges affords it some protection from collection, however encroachment of scrub and coastal erosion pose a conservation risk. We present data from a 20-year survey of populations in Kent revealing a fifteenfold fluctuation in annual abundance. We also report the astonishing recent discovery of a thriving meta-population of O. picridis in brownfield sites in South Wales. Finally, in light of these dynamics, we provide practical recommendations for conservation of one of Britain’s most elusive and unpredictable species.