This study aimed to investigate the effect of summer irrigation on the phytochemical and morpho-physiological traits of Iranian saffron. In this paper, first, four irrigation regimes, including control (without summer irrigation), irrigation in early July, irrigation in early August, and irrigation in early September, were conducted using a randomized complete block design with four replications in a research farm in Khomein County, Markazi Province, Iran (2020-2021). Based on this, the data encompasses the information collection concerning flowering and leafing time, stigma yield, vegetative growth rate, and phytochemical compounds of stigma, specifically crocin, safranal, and picrocrocin. The results demonstrated that summer irrigation had significant effects on assessed characteristics. Additionally, summer irrigation enhanced saffron growth rate and stigma yield (p≤ 0.05). Furthermore, the irrigation in early August accelerated flowering time and prolonged the flowering period from 13.5 to 16 days. The highest dry weight of saffron stigmas and the best stigma yield was 12.08 g/kg of flower fresh weight and 7.08 kg/h, respectively, and the optimal levels of crocin, picrocrocin, and safranal content obtained from irrigated plants in early August. Therefore, irrigation in early September resulted in earlier leaf occurrence before flowering, with the highest leaf dry weight (274 g m2) and leaf length (39 cm). The findings showed that the applied summer irrigation, specifically in early August, was an effective and economically viable practice to enhance saffron yield and stigma quality. This irrigation treatment is easily applicable and would be recommended to producers for its potential economic benefits.
