Increasing mangrove forest areas is set as an urgent action of many countries since the ecological and social importance of mangrove forest have been becoming awareness worldwide. In this study, forty-two 500-m2 plots were established in 15-year-old Rhizophora apiculata plantations in six different provinces, southern Vietnam for data collection. Growth parameters, mud depths, and salinities were measured in all plots. Stem density, stem diameter and height, height under crown, crown diameter, diameter of root system, and aerial root number were significantly affected by planting sites with the highest values of 1,177 trees/ha, 15.0 cm, 18.3 m, 9.0 m, 3,7 m, 2,1 m, and 6,8 roots/tree for the best site, respectively; and 1,000 tree/ha, 6.5 cm, 7.0 m, 2.0 m, 2.2 m, 1.5 m, and 7.8 roots/tree for the worst site, respectively. Mud depth significantly correlated to diameter of root system and root number in the form of negative linear with R2 of 0.13 and 0.14, respectively. While salinity significantly led to increased stem height, stem diameter, crown diameter, and root system diameter in the form of positive linear with R2 of 0.41, 0.17, 0.22, and 0.61, respectively. It is concluded that a site with mud depths of 10-20 cm and salinity of 20-31 ‰ besides others should be selected for planting R. apiculata, a tropical mangrove tree for coastal and marine environmental protection.