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Ayurvedic texts lay down detailed rules for collecting medicinal plants, specifying the region, season, plant part and maturity at which each drug should be gathered. The Sushruta Samhita prescribes different seasons for roots, leaves, bark, flowers and fruits. Modern phytochemistry recognises that the content of secondary metabolites varies with season, plant age and developmental stage. This review examines the classical guidelines and appraises experimental studies that compared raw-drug quality across the six Ayurvedic seasons. Studies are few but consistent in showing seasonal effects. In Guduchi satva prepared in each of the six seasons, yield was highest in Shishira and lowest in Grishma, total alkaloids were slightly higher in Varsha and Vasanta, and colour and taste varied in the rainy season. In Ashwagandha root collected across six seasons, withanolide A was highest in Hemanta and extractive values highest in Sharad. In leaves of Vasa and Saptaparna, chromatographic profiles were richest in June–July and October–November. Most studies used a single site and year, few replicates and limited statistics, and they rarely tested whether seasonal differences affect pharmacological activity. Seasonal effects are also confounded by plant age and developmental stage. We conclude that the classical emphasis on season of collection is supported in principle. Specific classical recommendations require confirmation with multi-year, multi-site studies that link chemical markers to activity. Pharmacopoeial monographs and research reports should specify and justify the season of collection.