Abstract In spice basil (Ocimum gratissimum L.), contribution of leaves, stalks and inflorescences were 59%, 23% and 18% to total plant biomass and 80%, 1% and 19% to total oil yield, respectively. The leaf oil was richer in eugenol but simultaneously had lower (E)-Î²-ocimene, compared to the inflorescence oil. Harvesting at pre-flowering produced 12.5%, 24.1%, 35.5% and 50.0% higher biomass yield compared to harvesting at 25%, 50%, 75% and 100% flowering, respectively, in the first year of cropping. The respective increase was 16.8%, 22.0%, 38.2% and 63.2% in the second year. Late harvested crop (100% flowering) contained the highest amount of essential oil and it decreased in the order of harvesting at 100% flowering > 75% flowering > 50% flowering > 25% flowering > pre-flowering treatment. The total oil yield was, however, significantly higher (15.8â19.9% and 12.7â33.6% in first and second years, respectively) with pre-flowering compared to all other harvest treatments. Pre-flowering harvested crop produced oil containing the highest amount of eugenol and it decreased in the order of harvesting at pre-flowering > 25% flowering > 50% flowering > 75% flowering > 100% flowering treatment.