Rubus calvatus Rubus calvatus is a species of bramble endemic to the islands of Britain and Ireland.DescriptionRubus calvatus is a shrub with a red, furrowed, arching stem which bears numerous prickles. Each leaf has five non-overlapping leaflets; these are deep green and hairless above. Flowers are pink, and the fruit develops from September on.DistributionRubus calvatus is found in scattered sites in England, E Wales, and the north east of Ireland. The greatest concentration of locations are in the Pennines and Peak District in England.