The aim of the Parc Floral's Souterrain project is to produce lignicolous mushrooms on cultivation supports. These are then distributed via an AMAP (Association pour le Maintien d'une Agriculture Paysanne) and to restaurants. In addition, the organization occasionally donates unsold products and organizes mushroom-related activities in SEGPA (Adapted general and vocational education section) classes.

The site occupied is a former tunnel under the Parc Floral, linking the esplanade of the Château de Vincennes to the château entrance to the Parc Floral in Paris's 12th arrondissement. Temporarily disused before becoming a mushroom farm, this 403 m² underground passageway contains :

- a storage and order preparation room

- three fruiting chambers

This allows to grow different varieties of mushroom, such as shiitake strains in the first room, grey, yellow, pink, oestratus and pulmonarius oyster mushrooms in the second room, and poplar pholitotes in the third.