In the vicinity of the White Sea Biological Station (WSBS) of Moscow State University, Adder's tongue is found in great density near Kislo-Sladkoye lake. In the early 2000's this species was found growing in mass in some areas around the lake. In July 2014, we found a small population near the Lower Ershovskoye lake estuary. In order to clarify the distribution of Ophioglossum over Kindo peninsula, a coastline registration survey was conducted in order to map the fern's populations and reveal its growth conditions.

Three new populations were found corresponding to proposed characteristic plant associations and abiotic factors supposedly limiting the fern's distribution. Ophioglossum vulgatum grows on slightly sloping coastal meadows near separating sea bays. It requires sufficient light, moderate moisture with low salinity (0.5-5.0 psu) and a pH of 7.37-8.65. Adder's tongue is accompanied by Poa pratensis L., Blysmus rufus (Huds.) Link., Rhinanthus minor L., and Parnassia palustris L. The population is limited by a Dianthus superbus L. zone from one side and Lathyrus japonicus Willd. with Cornus suecica L. from the other side.