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As climate conditions shift, certain tree species may experience increased productivity or could be negatively affected, leading to a shift in water use and carbon uptake. This research used leaf phenology, sap flow measurements, and photosynthetic rates to study species-specific responses to environmental drivers. Vapor pressure deficit and photosynthetically active radiation exhibited the strongest influence on daily sap flow rates across species. Green ash ( Fraxinus pennsylvanica Marshall ), which exhibited the lowest stomatal densities, did not regulate water use under periods of low water availability. Alternatively, swamp chestnut oak ( Quercus michauxii Nutt ), which had the largest stomatal densities and used 62% less water in the drought year, exhibited stomatal regulation under periods of low water availability. These findings can be used to estimate forest water budgets, which can improve land surface models and identify species in this forest type that will be most successful under future climate conditions.