RESUMEN
The chemical composition of essential oils and essential oil yield obtained from Rosemarinus officinalis (family Lamiaceae) and Lavandula angustifolia (family Lamiaceae) were determined in two harvesting times. Their essential oil was determined by hydro-distillation, and analysed by GC/MS. The results showed that harvesting time had significant effects on the oil content and compositions in both plants. The maximum essential oil percentage was obtained in full flowering stage in rosemary. Also and in lavender maximum linalool percentage (19.2%) was obtained in full flowering, and minimum linalool percentage (0.2%) was shown in the other time. Also the concentration of β – pinene (2.1%), δ-3-carene (1.5%), β – phellandrene (6.6%), Camphor(10.6%), Cryptone (0.8%), α- terpineol (2.3%) and Linalool acetate (1.2%) were higher than befor flowering stage. Therefore the harvesting time have a great importance in the production of essential oil and influenced on the quantity and quality of essential oil. As consequence, the best harvesting time in both medicinal plants was obtained in full flowering stage.