This is a multidisciplinary research project aiming at the conservation of Belgian vascular plant species lissted on the Habitat Directive, in casu Apium repens and Luronium natans. It includes a  taxonomical study of A. repens of both species. Their environmental requirements are studied, as well as the vegetation where they occur. Demographical measurements are made in different populations in order to characterize the populations and their status, and to identify the major threatening factors.