Campanula alliariifolia Willd. is a promising ornamental crop for container gardening in human settlements. The species is listed in the Red Data Book of the Volgograd region. The aim of the work is to study the effect of Bacillus subtilis alone and in combination with salicylic acid on the decorative qualities of the Campanula alliariifolia. The experiment was carried out in culture based on the collection site of the South-Ural Botanical Garden-Institute in 2021–2022. The effect of growth regulators on the phenology, growth dynamics, some morphometric indicators, the level of individual variability and the evaluation of the decorative qualities of C. alliariifolia was studied. The analysis of growth dynamics showed that during the study period, the maximum increase per day was observed in plants inoculated with B. subtilis. The degree of individual variability of the biometric parameters ranged from 6.1 (leaf thickness with B. subtilis) to 87.9% (number of flowers in an inflorescence with the combination of B. subtilis with salicylic acid). A two-factor analysis of variance showed that the effect of factor A (seasonal variability) was significant for flower and plant height, leaf length and width, inflorescence density and number of flowers in an inflorescence. The proportion of variance of the parameters ranged from 35.8 to 83.9%. The effect of factor B (different experimental options) and A×B is statistically significant only for flower diameter. There is only an average correlation between the diameter and the height of the flower. Only the flower characteristics are strongly related to each other. The study showed that the optimal option for increasing the scores for ornamentality, flowering frequency and inflorescence density of C. alliariifolia is to inoculate the plants with B. subtilis.