The Botanical Garden is an ex situ biodiversity collection of about 10 000 plant species. These collections serve scientific and educational purposes.

The greenhouses are a safe haven for tropical and subtropical plant groups. There are three large public greenhouses and more than 20 smaller ones which are dedicated to specialised collections. The latter are not open to the public. 
Hardy plants are grown in one of the many open air collections. They are either arranged along thematic lines (rock garden, Mediterranean garden) or according to their phylogenetic relationships (systematic collections).