The thermal stress caused by high temperatures on cut rose flowers grown in greenhouses is a major environmental impact that reduces the yield of growing cut rose flowers during summer. To confirm the resistance of grafted cut rose flowers to high-temperature stress, roses were grown in a greenhouse during the summer season and analyzed for yield, quality, root activity, and photo-physiological characteristics. A morphological change was observed in the stomata of the grafted cut rose flowers, which were larger in size than the scion or rootstocks. As a result of cultivating cut rose flowers by lowering the temperature of the greenhouse through shading in summer, it was confirmed that all of the scions, rootstocks, and grafted cut rose flowers were not in a stressed state by observing the maximal quantum yield of primary photochemistry (FV/FM) values on the chlorophyll-a fluorescence. However, the rate of electron transport flux from the primary acceptor (QA) to the secondary acceptor (QB) per the photosystem II reaction center (ET0/RC) value was found to be significantly higher on grafted cut rose flowers, compared with that of the scions. The efficiencies of the photosynthesis rate, the transpiration rate, and the stomatal conductance were increased when grafted compared with non-grafted. When the root activity was confirmed by the formazan content, it was found that the root activity was improved grafting. Furthermore, when grafted, morphological changes such as flower size and the number of petals on spray roses were also observed. Although there was a difference depending on the type of rootstock, the yield of the grafted cut rose flowers increased by 11–20%, compared with the scion rose. Therefore, grafting cultivation during the summer season with high temperatures is an effective method in terms of photo-physiological response and yield.

Cut roses are grown throughout the four distinct seasons of spring, summer, autumn, and winter in Korea. Especially in the very hot or cold seasons of summer or winter, the temperature and light environments inside a greenhouse cause abiotic stress on the growth of horticultural crops. In a greenhouse where shade cultivation is performed in summer, the temperature is high and the light intensity is low, whereas in winter when shade cultivation is not performed, both temperature and light intensity are low. This experiment investigated the year-round growth and yield changes of cut roses grafted onto three rootstocks. The root activity of rootstocks was generally higher than that of the scion. The stomata of the grafted cut roses showed morphological changes according to the seasons. Compared with the scion, the stomata of grafted cut roses became smaller and their number increased in summer, whereas only the stomata size increased in winter. The grafted cut roses had characteristics of high photosynthetic efficiency such as photosynthesis rate, stomatal conductance, transpiration rate from rootstocks under harsh environmental conditions including temperature and light intensity, and thus the photosynthetic efficiency was higher than that of the scion. There was no significant change in the yield of grafted cut roses, but flower quality parameters such as the stem height, stem thickness, and weight of grafted cut roses were improved according to the rootstocks compared with those of the scion. In particular, in cut roses grafted with R. multiflora cv. Natal Briar and Rosa indica ‘Major’ rootstocks, the weight increased as the stem lengthened and thickened in spring, autumn, and winter. Therefore, grafting is effective in improving the quality of cut roses grown under abiotic stress caused by harsh temperature and light intensity conditions during winter.

Cut roses are ornamental crops that are produced year-round, and the quality and yield of these cut flowers vary depending on the temperature and light intensity of the four seasons. Grafting improves productivity by increasing adaptability to negative environments, such as high temperature and low light intensity. The effectiveness of grafting depends on the type of the scion and rootstock. In order to confirm the effectiveness of stenting on roses, two varieties of cut roses (Rosa hybrida cv. Pink Beauty and Pink Shine) were grafted onto three rootstocks (R. multiflora Natal Briar, R. indica Major, and Rosa multiflora Hort. No. 1), which are widely used in cut rose, and the quality and yield of the cut flowers were investigated year-round according to the four seasons; then, principal component analysis (PCA) was performed. The Rosa hybrida cv. Pink Beauty (PB) used as the scion showed high yield and excellent growth in autumn when the light intensity was high and the temperature was low. The PB grafted onto the R. multiflora Natal Briar (NA) rootstock showed improved growth in spring, autumn and winter, excluding summer, and had the effect of lengthening the stem. The growth of PB grafted onto R. indica Major (RI) rootstock was also improved in spring, autumn, and winter, except summer, and in particular, the stem was lengthened and thickened. The rosa hybrida cv. Pink Shine (PS) was a variety whose yield of cut flowers increased in summer when the temperature was high. The PS grafted onto the three rootstocks gave a higher yield of cut flowers than the PS scion. The graft of PS/Natal Briar gave longer stems than the PS scion, and the graft of PS/Major gave thicker stems than the PS scion. PS grafted onto the Rosa multiflora Hort. No. 1 (N1) rootstock gave more petals than the PS scion. As such, cut roses grafted onto the Rosa canina cv. Natal brier (NA) improved the stem length, increasing the adaptability to relatively high temperatures, and the Rosa indica cv. Major (RI) improved the stem length and stem diameter, enhancing the adaptability to relatively low temperatures.