This aquatic buttercup with a wide, almost cosmopolitan distribution is present in all regions of Italy. It grows in still or slowly flowing waters which are rather rich in nitrogen compounds, rooting on muddy soils that are rich in bases, but usually poor in calcium, from sea level to the montane belt. The species is rare in the central belt of the Sardinian temporary ponds. The whole plant, when fresh, is toxic for the presence of an alkaloid (protoanemonine). The genus name, the Latin for 'little frog', was used since ancient times only for the aquatic species of the subgenus Batrachion, also a diminutive of the Greek 'batràchos' (frog); the species name in Greek means 'with hair-like leaves'. Flowering time: July to August.

Italian name(s): Ranuncolo a foglie capillari comune (Italia), Ranuncolo d'acqua comune (Italia), Ranuncolo tricofillo comune (Italia), Zein (Emilia-Romagna, Reggio).