The discovery and the excavation, in the years 2000, of a Gallo-Roman well on the site of Ch√Ęteaubleau, was an opportunity to organize a multidisciplinary study of the structure. Not far from one of the most important Gallo-Roman sanctuaries of the Senones, Well F123 appears different from the other remains in the ancient built-up area in the particularity of its results. By cross-referencing archaeological, environmental and historical data, this paper purports to shed a new light on certain taxons systematically considered as weeds. Traduction : Margaret & Jean-louis CADOUX