Spring broccoli production in the southeastern and mid-Atlantic United States has become increasingly vulnerable to high temperatures and variable rainfall. To address this challenge, a multistate trial was conducted to evaluate the performance of eight broccoli cultivars across seven states (NC, VA, GA, AL, MA, MI, IN). The objectives were to assess plant growth and yield performance under heat stress and to determine cultivar-specific normalized difference vegetation index (NDVI) thresholds that could predict marketable yield. Each trial site implemented a completely randomized block design with four replications and standardized plot dimensions (30 plants per plot in double rows on black plastic mulch). Fertility and irrigation were managed according to site-specific recommendations and monitored through soil testing and evapotranspiration estimates. UAV-based RGB and multispectral imagery was collected biweekly (4–12 weeks after transplanting) at midday under clear-sky conditions. Soil samples, weather data, and pest control measures were recorded at each location. Results showed that each cultivar exhibited a distinct NDVI profile correlated with crown greenness and morphology. Cultivars such as ‘Eastern Magic’ and ‘Green Magic’ maintained acceptable head quality and yield despite elevated temperatures, suggesting suitability for late spring planting. The use of NDVI imaging proved to be a promising tool for identifying cultivar vigor and optimizing management decisions during periods of heat stress.
