This three-year study monitored the growth stages of eleven Opuntia ficus-indica ecotypes in semi-arid Tunisian conditions from 2018 to 2020. A chronological calendar was developed to elucidate the phases and durations of these growth stages. In 2018, the duration of the floral bud phase varied across ecotypes, though the differences were minor. A similar pattern occurred in 2019, while in 2020, there were more noticeable variations, with the Sbitla (SBT) and Tala (TAL) ecotypes showing shorter phases. Although the flowering and fructification periods exhibited variation across the three years, the mean duration remained consistent across different origins. Notably, the INRAT Tomentoza (TTT) ecotype exhibited a curtailed fructification period in the initial year. Fruit ripening periods differed over the three years, with variances among ecotypes, although overall averages were not significantly different. The fruit development period (FDP) showed variability, with some ecotypes exhibiting lower FDP in the first year. However, the average FDP across three years did not show significant differences among ecotypes. A beta sigmoid growth model linking the duration of different phases to the number of floral buds, flowers, and fruits accurately described dynamic changes in these parameters during the growing season. Ecotype -specific variations were observed, with Borg Elafareg Beja (BEB) and Matmata (MAT) ecotypes consistently showing the uppermost values. Significant variations in the percentage of flowers and fruits were noted among ecotypes and study years. The ecotypes of Matmata, Ain Bou Dries, and Sbitla demonstrated a more robust flowering and fruiting process over the three years, maintaining percentages above 70%. This comprehensive study enhances our understanding of O. ficus-indica growth stages, highlighting the influence of ecotype and study year on phenological parameters. The model used is a valuable tool for predicting the number of floral buds, flowers, and fruits, during the growing season contributing to knowledge of cactus pear cultivation in semi-arid and arid climates.