The effects of MC on phenological and morphological components of earliness in short- (cv. TAMCOT CAMD-E) and full- (cv. Stoneville 213) season cotton were evaluated to assess its effectiveness in altering development and maturity when applied at 3 different stages of crop development. Among the 17 variables evaluated, all, except days to first open boll, total bloom, bloom index, vertical flower-interval and number of vegetative branches were affected by MC in ST 213, whereas, only horizontal-flower-interval, distance of fruiting branches, fruiting node distance, plant height, canopy width and percent first pick harvest were affected in CAMD-E. Response in ST 213 were in most cases observed in early and recommended dates of application. Plant height and canopy width were significantly reduced by MC with greatest influence observed up to 14 days after treatment. Correlation analysis showed that MC-induced earliness of maturity in Stoneville 213 was associated with changes in plant morphology. Results suggest that full season types are more flexible in their response to MC than the shortseason types in maturity modification despite having similar changes in morphological characters following treatment with the compound.