Cauliflower Yield, Growth, and Physiological Responses to Environments, Fall Planting Dates, and Cultivars in North Dakota

Environmental stress and suboptimal planting schedules are among the most significant factors limiting cauliflower production by disrupting developmental timing, reducing photosynthetic efficiency, and compromising curd quality. This study investigated the effects of growing environment (high tunnel vs. open field), planting date (10 July, 25 July, and 10 August), and cultivar selection (Amazing, Cheddar, Clementine, Flame Star, Snow Crown, and Vitaverde) on yield components, root morphology, vegetative growth, and physiological performance in cauliflower (Brassica oleracea var. botrytis) across two growing seasons. Field environment, planting date, cultivar, and their interactions were found to be significant for all parameters (p < 0.05). In general, open-field production achieved higher yields than high tunnels and shortened maturity, and early transplanting (10 July) maximized performance, producing a higher yield and larger curd size, while delaying to August 10 reduced the yield by ~49% and curd diameter by ~24%. Among cultivars, Flame Star, Snow Crown, and Cheddar were the highest-yielding cultivars overall, whereas Vitaverde performed the poorest. Under early planting, Flame Star showed exceptional productivity (1528 g), curd diameter (19.4 cm), and root development. Late planting decreased root biomass by ~38%. Physiological responses varied across environments and planting dates, with high tunnels showing greater stomatal conductance and transpiration, open-field plants exhibiting higher water-use efficiency, and early July plantings maintaining superior photosynthetic performance compared to later schedules. Correlation and hierarchical clustering analyses demonstrated strong integrated relationships among yield, curd diameter (r = 0.94), fresh root weight (r = 0.62), and root dimensions. Overall, it was concluded that open-field cultivation combined with early July planting using high-performing cultivars such as Flame Star, Snow Crown, and Cheddar significantly optimized cauliflower production by maximizing vegetative growth, enhancing resource acquisition, and ensuring optimal curd development. Early planting strategies emerged as the most effective approach, demonstrating up to 108% yield advantage over delayed schedules. These findings suggest that environment-adapted cultivar selection and strategic temporal management offer a viable approach to enhancing cauliflower productivity under variable climatic conditions.