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Four populations of Betonica bulgarica Degen et Neic. at Sinite Kamani Natural Park were morphologically tested. Intrapopulation and interpopulation variabilities were established. The relationship between morphological variability, number, area and ecological appurtenance of the studied populations were explored. The results demonstrated that the main source of phenotype variation is intrapopulation variability, mainly due to the age structure of populations. The most variable traits are height of stem and dimensions of leaves. The registered interpopulation variability was affected by the differences in altitude, soil type and differences in environmental conditions and soil properties. Indumentum and morphology of generative organs had taxonomic significance for distinguishing B. bulgarica from the other species in the genus, including the species that were morphologically most similar to it – Betonica officinalis L.