Abstract Planned studies were carried out to determine the most appropriate stage of economic harvest in Tagetes minuta by examining dry matter partitioning, essential oil yield and quality of oil at different growth stages grown in Lucknow conditions at the Central Institute of Medicinal and Aromatic Plants, Lucknow, India, during winter season 2002â2003. The maximum essential oil yield (1.01 g/plant and 56.1 kg/ha) was obtained upon harvesting at post fowering stage (seed setting stage). Advantage in essential oil yield at this stage was 130%, 34.5% and 36.5% yield enhancement over pre-flowering, 50% and 100% flowering stages, respectively. Flowers and leaves contained the maximum essential oil 2.14% and 1.89% (dry weight basis), respectively. Relative contribution of leaf, flower and stem to essential oil production was 40.7%, 37.8% and 21.5%, respectively. In the oil quality analysis, dihydrotagetone (77.1%) was the predominant component in oil from the leaves while (Z)-Î²-ocimene, limonene and (Z)-tagetone were the major constituents in the flower oil. The study suggests that T. minuta should be harvested at the post-flowering stage for realizing maximum essential oil yield and its desirable major chemical constituents. The study also differentiated the quality of leaf and fower oil for chemical constituents.