Effects of continuous extreme hot and drought weather on Hemerocallis hybridus growth

In the summer of 2013, Ningbo suffered the highest temperature in 60 years which lasted for long time associated with the drought. The injury degree and recovery situation of 18 Hemerocallis hybridus accessions under this weather conditions were recorded and the heat resistance of these germplasm were evaluated by graycorrelation analysis. There were difference between the field performance of different H. hybridus accessions under this continuous heat and drought. The growth of the accessions with strong heat and drought resistance were not affected by this weather. The growth of the accessions with weak heat and drought resistance were affected and performed yellow and wilt leaves. The indices included the growth, summer survival rate, overall posture, heat injury index, leaf color and ornamental value were selected as evaluation indices of heat resistance. The result showed that the accessions of X16, X8, X11 and X15 had stronger heat resistance. Their correlation degrees with the ideal species were over 0.9 which were suitable for cultivation and population in Ningbo area. The accessions of X1, X18 and X12 had weak heat resistant which were suitable for understory flowers as their faster recovery.