The results were presented of the study of the seasonal dynamics of alkaloid content in the aboveground and underground parts of T. foetidum and T. collinum. The studies were carried out to determine the possibility of using these plants as raw material for the production of biologically active alkaloids. A higher alkaloid content was observed in the underground parts of the plants. Tertiary bases only were found in the aboveground parts of the plants. The length of various vegetation phases is described.