Beyond providing well-being and biodiversity in urban environments, vertical gardens can act as thermal shields for the buildings where they are installed. A fundamental component of this interaction with infrared radiation is the water content within the plant leaves. Observing the infrared reflectance spectrum of these leaves can provide insight into their water status. In the present study, we explore the use of diffuse reflectance spectroscopy in the near-infrared region (1200 nm to 2100 nm) as a tool to assess changes in leaf water content of vertical gardens in the city of Quito, Ecuador. Leaves were collected from two urban gardens and analyzed during both after an intense drought period exceeding four months (late September), and the rainy season (April). The results reveal a systematic change, in the order of 10%, in the diffuse reflectance values within spectral regions associated with water absorption. This indicates that, despite a visually healthy appearance, physiological changes related to water content are indeed occurring in the leaves. These changes could potentially impact on the long-term health of the garden. A possible solution would be to monitor the garden using diffuse infrared spectra, whereby irrigation systems could respond to potential water stress levels with a greater degree of accuracy.