An experiment was set up to investigate the physiological growth and development response of different transplants of the African eggplant (Solanum macrocarpon L.) to varying irrigation water management regimes in the rainy and dry production seasons. Six (6) and 4 week-old transplants of the crop were cultivated in pots and treated to reduced irrigation (80% crop water requirement, CWR), optimum irrigation requirement (100% CWR) and over irrigation (120% CWR) in both cultivation seasons. Differences in plant height, leaf production, canopy spread, leaf area, and fresh and dry root weights of the crops were evaluated to determine the response of the transplants to the different irrigation treatments. It was observed that crop physiological growth and development was progressively enhanced with increasing irrigation from the reduced irrigation of 80% CWR to the 120% CWR regime where 20% more water was applied over the optimum irrigation requirement. Effect of the irrigation regimes, transplant age and their interaction were mainly significant in the dry season. Some physiological growth parameters also recorded some significant differences in response to the different treatments in the rainy season. The 6 week-old transplants gave the best physiological growth performance suggesting that transplanting Solanum macrocarpon at the appropriate age (6 week-old) with adequate irrigation resulted in higher quality leaf production, taller plants, wider crop canopies, broader leaves and adequate root development. Irrigation water use efficiency ($I_{WUE}$) in marketable and edible yields increased with decreasing irrigation water application and was highest at the 80% CWR and least at the 120% CWR. The 6 week-old transplants showed slightly higher water use efficiency than the 4 week-old transplants. Application of appropriate irrigation water management strategies in the dry season, where water is limited, and supplementary irrigation in the rainy season has the potential to promote vegetative growth, crop physiological development and stabilize income of farmers.