We are concerned here with a possibility of dipole matrix element strong blockade for excited atoms in the vicinity of Förster resonance. The latter occurs when the difference ∆δ = δ_l ^′ −δ_l between the quantum defects of l-and (l^′ = l±1)-adjacent series becomes equal to 0.5. The comparison between lifetimes of Rydberg p-states in alkaline atoms indicates anomaly large (fivefold) values in the case of sodium. We explain this fact with the configuration of p-and s-series in Na which practically meets the Förster resonance realization requirement. Important specific futures of the Förster resonance discussed here and related to radiative kinetics of Rydberg states are of interest for interpretation of fluorescence spectra observed in astrophysics.