Herbs are used as a source of medicine in Ayurveda and also in some traditional systems of medicine as having lesser side effects and cost when compared with the synthetic drugs. Plants live on a planet with days and seasons, and that affects their phytoconstituents. Availability of active principles in medicinal plants change by seasonal fluctuations, so their dose pattern for therapeutic efficacy also gets influenced. The best duration for the harvesting of specific secondary metabolites for better yield is not fixed. Seasonal impact show changes in important constituents like polyphenol, flavonoids, glycosides, alkaloids and essential oil. Late summer is the best collection time for essential oil component. Winter is the best season for harvesting of secondary metabolites containing plant parts. The results of these studies may help to the researcher those are involved in exploring the isolation of valuable chemicals from the plants for treatment of various diseases. Therefore, current review aims to focus on the best possible season for the harvesting of pharmaceutically important plant materials.
