A photosynthesis-based irrigation system is a novel approach to nursery crops irrigation management and could conceivably reduce water use during production. Experiments were conducted to determine the plausibility of a photosynthesis-based irrigation system. Cuttings, seedlings, and grafted (self and reciprocal) plants from two woody genera (Hibiscus rosa-sinensis, Cornus florida and Cornus kousa) were tested. To determine if the plants responded similarly to reduced substrate moisture, gas exchange was measured over a range of substrate moisture contents. Photosynthetic rates remained near maximum over a wide range of substrate moisture contents. Moisture response curves were similar among the species and among cuttings, seedlings, and grafted plants. A sigmoidal equation best represented the relationship between photosynthetic rate and substrate moisture content.