At its conception (in 1824), the library was quite modest, and would stay that way throughout the 19th century. It developed slowly through acquisitions, gifts, and bequests. Its expansion began at the beginning of the 20th century, and more precisely when Emile Burnat, a botanist from Vaud, donated his valuable botanical collection of 3 000 volumes to the City of Geneva. It contained elements of the collections of Louis Leresche, Samuel Bridel and Judge Abraham Thomas. Soon afterwards, the Rockefeller Foundation ensured that subsequent new acquisitions could be made.
In 1920, the famous library of De Candolle was donated by the family of the last living botanist of this name. This marvelous family collection can be compared to those of the largest national museums. Another valuable element to be added to the Conservatory was the Boissier library: it was given as a permanent gift in 1943 by the University of Geneva who had received it through the generosity of the Boissier family. Afterwards, the Library was able to acquire useful complements to its collection, such as the library of the “Société botanique de Genève” and the “Société genevoise d’horticulture” as well as those of the “Institut de botanique générale” and of the “Laboratoires de pharmacognosie et de pharmacie galénique” of the University.
Since then the City of Geneva, the guardian of these riches, has kept the Library up to date through regular acquisitions.
Today, the Library contains about 120 000 volumes. It has a fine collection of pre-Linnaean works from the 16th and 17th centuries. It also has a remarkable series of folios and botanical quartos of the 18th century, many of which are decorated with engravings. It contains essentially all works and articles in the field of floristics as well as on the taxonomy of plants. One can also find a collection of works relating to the voyages and botanical exploration, books on applied botany and a comprehensive collection of the other branches of botany.