A water tank system for plants comprising: - a container tank (1) adapted to receive water and soil in two superposed compartments, the bottom of this container container being watertight as it forms a compartment lower (2) sealed, adapted to receive water, while the upper compartment is adapted to receive the culture soil - a partition (4) horizontal separation, placed in the container container (1) and constituting the bottom of the upper compartment (3) adapted to receive culture soil - at least one capillary element (7) immersed in the water reserve by its lower part, and through the partition (4) of horizontal separation to have at its upper part a surface (5) of contact with the earth - a conduit (12) for filling the water reserve from above, characterized in that the capillary element (7) consists of at least one massive block in capillary material, preferably in calca tender, able to retain by capillary a volume of water at least equal to one-sixtieth of the volume of soil of the upper compartment, and to restore it as and when the plants require it by an increase in their suction voltage. This thanks to the distributed prositiousness of capillary material (7) and its tortuosity.Système de bac à réserve d'eau pour plantes comportant : - un bac-conteneur (1) adapté à recevoir de l'eau et de la terre dans deux compartiments superposés, le fond de ce bac-conteneur étant étanche car il forme un compartiment inférieur(2) étanche, adapté pour recevoir de l'eau, alors que le compartiment supérieur est adapté pour recevoir de la terre de culture - une cloison (4) de séparation horizontale, placée dans le bac-conteneur (1) et constituant le fond du compartiment supérieur (3) adapté pour recevoir de la terre de culture - au moins un élément capillaire (7) plongeant dans la réserve d'eau par sa partie inférieure, et traversant la cloison (4) de séparation horizontale pour avoir à sa partie supérieure une surface (5) de contact avec la terre - un conduit (12) de remplis
