The Botanical Gardens feature a wide variety of plant specimens from countries with a Mediterranean climate, showing the great similarity between the landscapes of California, Chile, South Africa and Australia, and the Mediterranean basin. Unlike other museums with collections of non-living materials, the Gardens are a constantly evolving, dynamic space. New species are grown every year in the nurseries and planted out in the grounds. The ones that fail to adapt to the climate or soil characteristics are removed from the collection.

The Botanical Gardens are home to some 1,350 species, although the eventual aim is to grow 4,000 Mediterranean species from around the world. The species are grouped together in a recreation of their natural ecosystems.

The Botanical Gardens were created to contribute to the ex-situ conservation of Mediterranean biodiversity, mainly focusing on species from Catalonia. The Gardens are the ideal place to grow and exhibit plant species that are under threat. They also disseminate knowledge about which species need protecting and the actions to be taken in order to achieve this aim.