For the first time, changes of the growth and accumulation of phenolic compounds (PHCs) in dif ferent parts of underground organs of the tuberoid orchid Dactylorhiza maculata during vegetation and the winter dormancy period were studied. It was shown that the replacement of old tuberoids and adventitious roots by new ones is accompanied by active growth, assimilates reallocation, and PHCs accumulation. It was found that the tuberoid performing the function of a storage organ possessed a low PHCs content, which increased at the end of vegetation and was stably high during the winter dormancy period; in spring the con tent decreased, mosr likely as a result of PHCs catabolism and utilization for growth processes. It was pro posed that the higher PHCs content in adventitious roots and tuberoid terminal parts is determined by mycotrophy of the organs.