This study was preliminary to developing feed-forward computer control algorithms to irrigate Acer Rubrum(Red Maple) trees in proportion to predicted transpiration. Transpiration rates of Acer Rubrum and related climatevariables were measured continuously in a very high evaporative demand greenhouse environment and comparedindependently to solar radiation and vapor pressure deficit (VPD). Measured transpiration rates were further comparedto predicted transpiration based on the combination equation. Based on regression analyses and the coefficient ofdetermination (R 2 ), the single variable VPD predicted transpiration equally as well as the combination model with an Rsquared value for both equal to 0.861. Meanwhile, using the single variable solar radiation to predict transpirationresulted in an R squared value of 0.652.