<p>Phenology is acknowledged as one of the important traits that contribute significantly to the success of alien species. Differences in the life history traits related to invasive and native vegetation have been shown to influence the success and extent of the plant invasion. Therefore, to obtain this information, we documented and contrasted the duration of key phenological events viz., vegetative, reproductive and senescence between an invasive alien plant species <i>Ageratina adenophora</i> (Sprengel) King and Robinson and associated 29 natives in different habitats viz., Oak, Pine and Cypress forests and grassland. The results indicated vegetative phase and senescence tends to be more synchronised between species than in reproduction. Distinct periodicity in the reproductive phases between <i>A. adenophora</i> and the associated species was observed, with <i>A. adenophora</i> flowering earlier than most of the other species in all habitats. The reproductive cycle of <i>A. adenophora</i> was over before the onset of rainy season which enabled dispersed seeds to optimize the growing condition provided by the rain, giving head start over associated species. Senescence phases in <i>A. adenophora</i> was longest compared to associated species. The observation made in the study may assist in understanding the phenological behavior of <i>A. adenophora</i> and associated species, and may develop a guideline for future mechanistic management of <i>A. adenophora</i>.</p>