The concept of Vertical Cities has emerged as a response to rapid urbanization and limited land availability, promoting the construction of high-rise buildings. These structures, however, significantly contribute to energy consumption and greenhouse gas emissions. However, Vertical Greening Systems (VGS) which integrates plants into building facades, presents a sustainable solution by reducing external and internal temperatures, thus decreasing the need for heating, ventilation, and air conditioning (HVAC). This research investigates the application of Vertical Greening Systems (VGS) to improve energy efficiency in high-rise buildings within Millennium City, Kaduna State, Nigeria. By reducing cooling loads, VGS can significantly lower energy consumption in high-rise buildings. This study investigates the impact of VGS on energy efficiency in high rise buildings within vertical urban developments, focusing on the tropical climate of Northern Nigeria. The research employed a mixed methodology by conducting case studies and quasi-experimental approach. Using DesignBuilder software integrated with EnergyPlus, simulations were conducted for five plant species with varying Leaf Area Index (LAI) and foliage properties to assess thermal performance, both with and without VGS integration. Findings demonstrate that VGS integration reduces annual cooling demand by up to 25% with Hedera helix performing optimally. Results indicated that H. helix (common ivy) delivered the highest cooling load reduction, up to 23.6% annually, compared to other species. The results align with prior international literature and provide a replicable framework for evaluating species-specific VGS in tropical urban contexts. The research offers both theoretical insights and methodological advances in sustainable facade design. The study presents VGS as a viable passive design strategy for future vertical city in Millenium City, Kaduna.