In the study there are presented laboratory experiment results of the initial growth rate of 5 grass species: Festuca arundinacea, F. ovina, F. rubra, Lolium perenne and Poa pratensis (1 variety per each species), in mixtures with Medicago lupulina (variety Ekola), Onobrychis vi-ciifolia (variety Taja) and two varieties of Trifolium repens (Haifa and Nanouk). The assessment of the growth rate of seedlings was carried on the basis of measurements of root length and height of seedlings (in mm) for each variety in 5th, 10th, 15th, 20th, 25th and 30th day from the date of the sowing date. The study showed that the differences of grass species in mixtures with legume spe-cies have been caused by the biological and physiological properties of grasses and legumes. The seeds of Romina (F. arundinacea), Tomika (F. ovina), Alicja (P. pratensis), and Natara (Lolium perenne) variety in mixtures with all studied legume species have had the worst germination capac-ity than in control (one species sowing). Among the studied grass species, it was discovered the beneficial influence of root elongation variety Romina (F. arundinacea) but statistical analysis did not confirm the significant differences.