The problem of sexual differentiation of plants has always occupied a central place in the study of their biological characteristics, since the process of plant sexualization controls the quantitative and qualitative aspects of the formation of gametes and, ultimately, seeds. Seed production, in turn, determines the evolutionary fate of the species. Various chemical compounds are among the factors that change the plant sex in one direction or another. The question of the effect of pre-treatment with a cobalt complex compound on the sexual differentiation of plants is not covered in publications. The process of sexualization of plant organisms serves as one of the possible ways to increase plant productivity, therefore, the relevance of managing this process is obvious. The influence of pre-sowing chemical treatment of seeds on the process of sexual differentiation, growth and productivity of prickly-seeded spinach (Spinacia oleracea L.) was studied using generally accepted methods of conducting field experiments with annual herbs in field and laboratory conditions. The conducted studies allowed us to establish that with a decrease in the number of leaves and their size, the mass of spinach with female and male plants decreases in samples with pre-treatment with concentrations of dimethyl sulfoxide cobalt (II) chloride 0.05% and 0.1%, which indicates its inhibitory effect. The same concentration causes a gender change in spinach populations to the female side. It was also shown that the minimum concentration of 0.01% does not affect the morphological characteristics of spinach, except for the number of leaves of female plants, but increases the seed productivity of spinach. It was determined that with an increase in the concentrations of dimethyl sulfoxide cobalt (II) chloride to the values of 0.05% and 0.1%, the viability of pollen decreases sharply. The obtained data show that the biological and morpho-physiological characteristics of prickly-seeded spinach vary depending on the concentration of the complex compound of cobalt (II). The dynamics of changes in seed productivity is also in a certain dependence on the experimental factor. The study of the effect of pre-sowing treatment of Spinacia oleracea seeds with dimethyl sulfoxide cobalt (II) chloride on the process of its sexual differentiation allows, with further accumulation of experimental material, to predict the productivity of this plant for practical use as one of the most common and nutritious types of vegetable greens.