Chemical composition variability of the essential oil of Conyza canadensis Cronq.

The essential oils from different botanical parts (herb, leaves, flowers, stems, roots) of Conyza canadensis Cronq. were analysed at various ontogenesis phases. R‐(+)‐limonene and trans‐α‐bergamotene were the main constituents of the herb, leaf and flower oil at all phases of vegetation. The early flowering phases are the best time for harvesting C. canadensis herb, because the oil yield is the highest (0.7–0.8%) and its chemical composition is constant (limonene 80–81%, trans‐α‐bergamotene 6–8%). Limonene was the dominating compound of the oils of European origin (French, Italian, Spanish, Belgian, Bulgarian and Lithuanian).