We describe recent studies by park rangers in the Juan Fernández Archipelago National Park in relation to the National Conservation Plan of Critically Endangered Species. Species of endemic flora have been monitored over a period of three years, 2007 to 2010, on Robinson Crusoe and Santa Clara Islands. Phenology, number of individuals, location, habitat are described. This valious information improves the knowledge regarding several new populations of critically endangered plant species, strongly increasing in number of populations of many species, and it offer new strategies for improving conservation of these endangered species.