Introduction. In recent years, there has been an increase in fundamental interest in the search for effective, including microbiological, methods for processing pharmaceutical waste to obtain new biologically active compounds on their basis. Our results showed that the product of bacterial degradation of paracetamol (BDP) exhibits pronounced stimulating properties in relation to medicinal plants of the families Plantaginaceae, Lamiaceae, Urticaceae, Linaceae and can be used as an inducer of the accumulation of biologically active substances in them.Aim. The purpose of this work is to study the effect of BDP on the dynamics of biomass accumulation and the content of flavonoids in the flowers of Calendula officinalis L., fam. Asteraceae in comparison with the control (water) and growth stimulator "Zircon".Materials and methods. BDP obtained on the basis of the Laboratory of Alkanotrophic Microorganisms Institute of Ecology and Genetics of Microorganism UB RAS (Perm). Calendula officinalis flowers collected from plants treated with BDP and Zircon growth stimulator were used to study the dynamics of dry biomass accumulation and changes in the content of flavonoids by the spectrophotometric method. For a comparative analysis of the intensity of the increase in the biomass of flowers during the treatment of plants with these agents, as well as to predict the accumulation of flavonoids, kinetic modeling was used.Results and discussion. The total biomass harvest of calendula officinalis flowers when treated with BDP increased by 55 %, and when treated with the Zircon growth stimulator, by 24 % compared to the control. The content of flavonoids in flowers when treated with these agents increased by 101 and 40 %, respectively. The dates for the beginning of the collection of calendula officinalis flowers in the conditions of the Western Urals were determined: with the use of the Zircon growth stimulator – from July 20, BDP – from August 1, without treatment with growth stimulants – from August 14. Both stimulants increase the end date of the collection of raw materials by 10 days.Conclusion. The product of bacterial degradation of paracetamol has a pronounced stimulating effect on calendula officinalis, significantly increasing the biomass of flowers and the content of flavonoids in them compared to the control (water) and growth stimulator "Zircon". With the use of kinetic modeling, the values of the parameters of the growth rate of the biomass of plant raw materials during the treatment of plants with these agents were established, a forecast was made for the accumulation of flavonoids, and the timing of the collection of calendula officinalis flowers in the conditions of the Western Urals was substantiated.