Modern blocks of flats, for reasons of economy, include fewer and fewer balconies. They are replaced by French windows, giving onto the outside, protected by bars. The garnishing of these facade walls with flowers requires special superposed window-boxes, the shape of which enables young plantlets to face the outside. Watering or spraying these window-boxes poses the problem, in dry weather, of not spilling over onto the lower storeys. The problem may be solved by using capillary strips which ensure the water balance of window-boxes having a tank or alternatively associated reservoirs 6 which, depending on the position of the float 13, determined by the excess water, retain or release liquid into the window-boxes 4 via orifices 9 regulated by the valve needles 15.
