Rose (Rosa hybrida L.) ‘Asami Red’ plants were grown in a glasshouse for a year and the preharvest environmental parameters, and morphological and physiological parameters of individual cut flowers at harvest and during the postharvest period were recorded. Principal component analysis showed interrelations between the parameters: rose plants grown under “dry” conditions, i.e., high temperature, low relative humidity, and consequent high vapor pressure deficit, produced cut flowers having delayed wilting symptoms, resulting in a long vase life; cut roses with a high transpiration rate in the dark at harvest could not maintain their water relations properly, resulting in a shorter vase life; roses grown under “dry” conditions had small stomata and a low transpiration rate in the dark at harvest. These results indicate that humidity conditions are key preharvest environmental factor affecting the vase life of cut roses, and roses grown under “dry” conditions develop more functional stomata, regulate their water relations properly after harvest, and have a longer vase life. Multiple regression analysis to predict the vase life from preharvest environmental parameters and morphological and physiological parameters at harvest generated a significant equation (Y = −0.0971·X₁ + 0.0242·X₂ − 0.3275·X₃ − 2.84792·X₄ − 0.4859·X₅ + 15.397, where Y is the number of days of vase life; X₁−X₅ are the daily minimum relative humidity, ratio of the stem diameter of the neck and cut end, stomatal width, water potential in the light, and transpiration rate in the dark, respectively; R² = 0.618; P < 0.001).