The results of the introduction in the North of the valuable medicinal plants – Hypericum perforatum and H. maculatum are presented. During the cultivation rhythms of growth and seasonal plant development were studied. It has been revealed that both types of plants from the second year of life regularly undergo a complete cycle of development of shoots and form seeds of full value. The quality of sowing seeds collected from plants in different years of life, weight of 1000 pieces, their size, laboratory germination have been studied in detail.