The purpose of this study was to investigate the effects of summertime water temperature and water quality surveys at the Osaka Prefectural Oizumi Ryokuchi Park Kakitsubata Garden, and to compare the results with the Ota-no-sawa iris habitat, which is the natural habitat of the iris. As a result of the survey from July 29th to October 1st, 2021, the water temperature in Oizumi Ryokuchi Park Kakitsubata Garden was significantly higher than that in Ota-no-sawa, with an average water temperature 5.9°C higher and over 40°C depending on the location. This is thought to be due to the difference in water source environment between the two sites. In order to investigate the relationship between water temperature and growth of iris, regression analysis was performed on the relationship between the average daily exposure time to water temperatures above 28°C and the height of the plant, and a significant relationship was observed. As a result, the shorter the exposure time to high water temperature, the longer the plant height. As a result of the water quality survey, the pH value of the iris garden was alkaline, and was outside the optimum pH value range for general plants. It was concluded that these two factors could be the cause of poor growth.