Determining the optimal lifetime of horse mint plants

The aim of the study is to determine the optimal terms of planting operation and the period of plant har-vesting in the phase of maximum accumulation of biologically active substances. Objectives: to study the features of bioproductivity and changes in economically valuable indicators of horse mint in the 1st–5th years of vegetation. The object of the study is horse mint. The studies were conducted at the Federal State Budgetary Scientific Institution VILAR in 2016–2024 in a medicinal crop rotation. Vegetative propagation was used (in spring, by rhizome cuttings, annually, planting pattern 60 × 20 cm). Crop records were taken in the 1st–4th years of the crop vegetation. The content of essential oil in plant parts was determined in the phases of vegetative growth, budding and mass flowering using hydrodistillation. The content of flavonoids in terms of luteolin was quantitatively assessed using spectrophotometry after the complexation reaction with aluminum chloride. The duration of the vegetation period of horse mint does not exceed 140–170 days. The onset of the main phenological phases of horse mint was highly dependent on the meteoro-logical conditions of the vegetation season and varied within 10-20 days. Horse mint plants reached their greatest height by the beginning of flowering from the second to the fourth year of life. The raw material of horse mint was characterized by a high content of flavonoids (3.921–4.388 %). The maximum content of essential oil in the leaves of horse mint reached 1.8%. Inflorescences accumulated 1.2–7.1 % less essen-tial oil than leaves. The highest yield of leaves was noted in the first, second and third years of crop vege-tation, reaching on average 1.64; 1.70 and 1.59 t/ha of air-dry mass (leaf) in the first mowing, respectively. Starting from the fourth year of vegetation, a decrease in yield by 36.2% was observed compared to the third year of life. Plantings of the crop after the third year of vegetation became less productive due to a significant decrease in crop yield. Considering the decrease in yield and essential oil content in plants in the second cut, it is most rational to cultivate horse mint in the Non-Chernozem zone of the Russian Fede-ration using a single-cut cultivation system for three years.