Selection of high-quality tree peony varieties suitable for the south Yangtze River area

To select tree peony varieties with high ornamental value suitable for the hot and humid environment of the south Yangtze River area, 74 tree peony varieties from the Chenshan Botanical Garden in Shanghai were selected as experimental materials. The experiment involved initial selection for leaf humidity and heat tolerance, assessing the ornamental value during the flowering period of the following year and measuring a series of indicators such as the relative chlorophyll content of the leaves. Methods including principal component analysis, cluster analysis, and comprehensive membership function were employed. The results indicated that among the varieties assessed for humidity and heat tolerance, 43 obtained a composite score of 3.75 or above. Upon further assessment of the flowering period for these 43 varieties in the subsequent year, 14 varieties clustered in the top tier based on their scoring for ornamental value. Then, during the summer season, physiological indicators were measured for the previously selected 14 tree peony varieties. Combining these data with the comprehensive membership function, the humidity and heat tolerance of each variety were quantified. The synthesis of scores, combined with cluster analysis, revealed that varieties including 'Yinhong Qiaodui', 'Shengge Jin', 'Linghua Zhanlu', 'Baixue Gongzhu', 'Di Guan', and 'Cunsong Ying' exhibit both high ornamental value and tolerance to humidity and heat, making them suitable for cultivation in the south Yangtze River area.