A New Method for Determining the Calendar Age of Plants of Heracleum sosnowskyi and Evaluation based on the Age Composition in Cenopopulations of the Species in the North

Studies have been carried out to determine the calendar age of plants of the invasive species Hogweed Sosnovsky (Heracleum sosnowskyi Manden.). The study of the root structure showed the presence of growth rings formed by increments of secondary xylem, which makes it possible to use the xylochronological approach to estimate the calendar age of H. sosnowskyi. The number of xylem rings on the transverse section of the root corresponds to the number of remnants of annual increments on the longitudinal section of the underground caudex. The method of accounting for annual increments on a longitudinal section of the caudex is simple and effective and allows you to determine the age of plants of H. sosnowskyi in the field, without resorting to tissue contrast and microscopy. Plants of H. sosnowskyi in natural cenopopulations of the middle taiga zone of the Komi Republic, started flowering in the third year of life, and their calendar age reached 7 full years.