Introduction to the culture of new species of legumes, allocated from the native wild flora and creating high-protein varieties, fully used bioclimatic resources, adapted to the extreme conditions of the North, can solve the problem of overcoming the typical for the northern territories of protein deficiency of the bulky feed. To assess the potential productivity, the forage quality and the usefulness of using in the selection, within three years the biological, morphological, economically-valuable traits of the aboriginal ecotype Lathyrus maritimus Bigelow have been studied under conditions of natural grassland and the test field. Indicator of the potential productivity of green mass of the ecotype under conditions of natural grassland exceeded 200 c/hectare against the backdrop of fertilizers in dose P60K60.  The forage is characterized by good quality: crude protein-17,5-21,7%. The period of adaptation of the specimens in new conditions, regardless of the method of introduction, amounted to three years. Besides, only 38 of collectible 150 samples yielded a productivity equal to the natural analogues. According to the authors, method of vegetative propagation has proved more effective in comparison with seed reproduction, due to the Rhizobiums, carried over with rhizosphere of the rhizomes into the test field. In the options of the experience with the vegetative reproduction the effect of biological symbiosis was achieved due to the individual characteristics of the interacting organisms, which formed the optimum combination in vivo growth. In support of this hypothesis, the authors cite the comparative analysis of the basic physical parameters of virgin and arable alluvial soils, which defines the specificity of the transformation of the top organic and accumulative part of the profile and organic matter, and, therefore, the nature of the microflora. The arable soils composition of microbial cenosis does not contain effective strains for the north ecotype Lathyrus maritimus Bigelow. This leads to low efficiency of the seed propagation and slowly development of the introduced plants in the new conditions. In order to enhance the capabilities of plants to adapt and realize the potential agronomic traits at a higher level, identified priorities for further work in the selection of the varieties and complementary for them strains of the Rhizobiums.