Invasive species, such as Tamarix ramosissima, pervade riparian habitats throughout the American Southwest. Tamarix ramosissima poses a threat to native plant community structure due to its fast growth rate, high water use, and stress tolerance. Therefore, it is of great importance to find long-term, viable strategies to mitigate its invasion. Here, we test the hypothesis that Tamarix ramosissima is a shade intolerant plant, as understanding the plant’s ecology is necessary to employ an effective conservation strategy. We measured several functional traits, morphological traits, and flower number of Tamarix ramosissima within open and canopy habitat types to detect physiological responses to shade. The data show significant differences in photosystem efficiency, chlorophyll content, stomatal density, stomatal aperture, and flower number between open and canopy plants; there is also evidence of a reproductive tradeoff in shade plants between increased photosystem efficiency and chlorophyll content, and decreased flower number. These data indicate shade intolerance in Tamarix ramosissima, potentially suggesting that promoting native plant canopy cover could be an effective conservation strategy to restore native community structure.