The purpose of the Collection is research on the genus Hydrangea (introduction of new plants, identification, behavioural studies) and the dissemination of knowledge about the genus.

The collection was labelled as a national collection in 1999 by the C.C.V.S*.

It occupies an area of two hectares and includes about 2,000 subjects, including plants of 1,200 different species and varieties. These plants come from nature or from selections made by horticulturists over more than a century. It has been brought together by Corinne Mallet (Corinne Mallet-Hoyé), who began the collection in 1984.

Some of the plants in this collection are unique in the Western world. Most of them come from Japan, the home of a very large number of species belonging to the genus Hydrangea.

Visitors are lent a brief guide at the beginning of their visit to help them round the collection. At the end of their tour, they can take advantage of explanations and advice from Corinne Mallet-Hoyé or Robert Mallet, or else from volunteer members of the Shamrock Association.​

* C.C.V.S. – Conservatoire des Collections Végétales Spécialisées, French organisation for the protection of plant collections, equivalent to Plant Heritage in the United Kingdom.