Variability of the essential oil from three sorts of Echinacea MOENCH genus during ontogenesis The content and quality of the essential oil in relation to the main ontogenetic stages of plants were studied in three various sorts of Echinacea genus. The comparison included Echinacea purpurea, Echinacea atrorubens, and Echinacea pallida. The differences in the content of the oil in different parts of plants and the abundance of individual oil constituents in oils from the sorts under study at the optimum stage of ripeness for harvest were evaluated as well.