In 1968 the Holdridge Arboretum was initiated. It was a small area of cacao with an exceptionally rich overstory of native shade trees. Later the cacao trees were removed to facilitate the phenological study of the biologists Frankie and Baker.  In 1970, Gary Hartshorn continued planting seedlings of many native tree species, reaching close to 240 species. The Arboretum currently occupies 3.5 hectares, located at Sura trail (375 – 750m.) between Sura and Arboleda streams, the elevation varies from 33 to 45 m.a.s.l., presenting alluvial and semi-alluvial soils. Currently, this area encompasses 929 trees of 247 native and 3 exotic species, representing 63 families and 168 genera. In regards of structural groups, the arboretum comprises 216 tree species, 18 palms, 13 shrubs, 2 lianas and 1 tree fern.

The main goal of the Arboretum is to become an open classroom to facilitate the dendrological studies for hundreds of students and researchers visiting the station every year. For improving this learning process, we seek to continue adding trees to complete the 420 La Selva´s tree species. 247 native tree and plant species and almost 1000 individuals represent an immense and unique resource or representation of very rare species of the Humid lowland Rainforest,