Studies proved significant differences in dynamics of initial growth and development of grass species under tests. The sequence of species starting from the best up to the worst developed at the 21st day after sowing date was as follows: Lp, Bi, Fa, Fp, Ae, Dg, Php, Pha. Humidity level of peat-mursh soil had the significant effect on the growth and development of grass seedlings. In drier conditions, grass seedlings were lower, with less number of leaves and poorer tillered as well as they had worse developed the root system. Seedling sensitivity to soil drying decreased in a sequence: Pha, Php, Lp, Dg, Fp, Ae, Bi, Fa. Grasses sown late in summer were characterized by slower growth and development rates than those sown in May. Sensitivity to sowing term increased in a following sequence: Bi, Fa, Ae, Dg, Php, Pha, Lp, Fp.