The research aims to study the differences of some aspects of physiological activities in three ornamental plants, Conocarpus erectus L., Hibiscus rosasinensis L, and Vinca rosea L. grown in Makkah. These plants are founded in similar environmental circumstances (drought and rewatering). Through studying and comparing: Photosynthetic activity, maximal productivity, strategies of drought tolerance, transpiration and hardening. Determining of the most suitable environmental and agricultural conditions of each plant species mentioned above have been achieved.