The species diversity in the Talamanca Mountains is probably unequalled in any other area of equivalent size in the world, according to the United Nations’ World Conservation Monitoring Centre.

Monte Azul’s rich forest land boasts a large number of epiphytes, tree ferns and bromeliads, as well as over 150 identified tree species. Also numerous are flowering plants, including many orchids of varying size and bloom, with flowers appearing throughout the year.

The range as a whole has some 10,000 flowering plants, over 4,000 non-vascular plants, approximately 1,000 fern species, 80% of the country's mosses and about 900 lichens. Levels of endemism are estimated at over 30%.

Tropical rainforest has covered most of the area for the past 25,000 years, since the last glaciation. Of the twelve life zones of Costa Rica, at least nine occur in the region. These include all five altitudinal zones found in the tropics, from lowland tropical rainforest to cloud forest. Monte Azul is located in the lower montane forest altitudinal zone (1,000- 2,500 m).