Foliar fertilization has become an increasingly common practice on golf courses around the world. While typically used as a supplement to traditional root-feeding programs, the importance of foliar fertilization has been magnified by the management practices of today's golf course superintendent. Often, a significant portion of the total annual nitrogen applied to golf course putting greens comes via foliar fertilization. Despite its widespread use, there have been relatively few research studies investigating foliar uptake by turfgrasses and no studies which document foliar uptake of nutrients in a field setting. A ¹⁵N isotopic tracer field study was conducted to compare the seasonal uptake of foliar-applied nitrogen by a cool-season (Agrostis stolonifera var. palustris (Huds.) Farw. cv. ‘Penn A1') and warm-season (Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy cv. ‘Tifeagle') turfgrass species managed under golf course putting green conditions. Foliar uptake measurements were compared to electron microscope observations and gas chromatographic analysis of the leaf cuticle, along with environmental and climatic data (wind speed, air temperature, leaf wetness, PAR, and relative humidity) known to affect foliar absorption. This research should provide foundational data on the uptake of nutrients by turfgrass leaves in a field setting, while examining the influence of cuticle dynamics and environmental parameters. Results should have a direct benefit to golf course superintendents who wish to utilize foliar fertilization in the most efficient manner.