Arboreta are composed of collections of plants belonging to different species of trees and shrubs, mainly of exotic origin. The plants are arranged according to taxonomic and geographical criteria; each plant is identified by a sequence inventory number associated to the scientific name of the species, as defined under the rules of botanical nomenclature. The original distribution area is also indicated for each species. Different scientific disciplines such as botany, forest ecology, sylviculture, ecophysiology, plant pathology, etc. may benefit by this type of collections. The didactic function also plays a key role for visitors as well as for students interested in furthering their botanical knowledge or in carring out studies on natural and biological sciences.
The function of conservation (ex situ) of forest biodiversity is important too, especially for species threatened with extinction. In Italy, the arboreta with exotic species are not numerous and certainly those of Vallombrosa are the most important ones (significant at a European level too) for historical reasons and number of individuals, species, subspecies, varieties and cultivars hosted. According to the last inventory made in 2011, there are nearly 1800 individuals and a total number of 656 separate units - including species, subspecies and cultivars.