The first part of the river runs through the Campo dei Fiori Regional Park. Up to 600 m of altitude, in this protected area, chestnuts, ash trees and linden trees prevail. Maples are common in the more humid valleys. On the summit of the Campo dei Fiori massif these plant species are replaced by beech, while birches and Scotch pines are common on the dry slopes of Monte Martica. The open spaces are embellished by now rare plants such as the Gentiana pneumonanthe and by dozens of species of wild orchids, such as, for example, the vesparia and the moscaria.