An experiment was set up in 1965 on the Isle of Rum to determine the reasons for poor vegetation cover on an exposed mountain ridge. Suggested hypotheses related to effects of grazing herbivores, site exposure or soil infertility. To test one of these, a 100 m2 experimental plot was subjected to a fertiliser regime over a period of three years with a vegetation survey and soil analysis conducted at the outset of the research period (1965), in 1969 and in 1996. Plant cover within the experimental plot increased from 5 % (1965) to 100 % (1996), and was maintained at this level in a recent monitoring (2010). A change from acidophilic plants dominated by heather to a grass/moss assemblage was also recorded within the plot over the monitoring period. Within an unfertilised control plot set up in 1996, plant cover had increased from 25 % to 50 % (2010), although there was little change in composition of plant species.