Compositional transformation of South African semiarid grasslands and savannas owing to changes in soil nutrient status and fire-linked attributes is often reported. However, mechanisms of change are not fully understood. Currently, plant-derived smoke has attracted much attention as a fire-related cue responsible for stimulating germination and seedling growth. However, there is very little documentation on how these fire-linked factors, such as smoke, and soil macronutrients, such as nitrogen (N), phosphorus (P), and potassium (K), interact to effect seedling growth of grasses. In this study, smoke-responsive (Themeda triandra) and less smoke-responsive species (Eragrostis curvula and Panicum maximum) were tested with different concentrations and combinations of smoke-water and smoke-isolated butenolide with or without added N, P, or K under greenhouse conditions. In the absence of N, P, or K, smoke-water and butenolide treatments enhanced a number of seedling growth parameters of T. triandra. In contrast, exclusion of N from the nutrient solution significantly reduced shoot length, seedling weight, root volume, and vigor index of E. curvula at all tested concentrations of smoke-water and butenolide solutions compared to the control. In the presence of N, P, and K, smoke-water and butenolide suppressed seedling growth of P. maximum, whereas the absence of one of these macronutrients had a small promotory effect on some parameters. This study may assist in understanding the postfire seedling dynamics of grasses.