Abstract: 【Objective】To investigate the dwarfing effect of plant growth retardants on Hemerocallis hence improve its ornamental value.【Methods】Different concentrations of Paclobutrazol（PP₃₃₃）,Uniconazole（S₃₃₀₇）,Chlormequat Chloride（CCC）,and B₉ were applied to Hemerocallis variety‘little Anna Rosa’ by pot soil application or leaf spraying with water as control. The effects of plant growth retardants on plant morphology,leaf characteristics,and flowering of Hemerocallis were investigated.【Results】All of the treatments had an inhibitory effect on‘little Anna Rosa’ plant morphology,with the treatment of spraying 60 mg/L S₃₃₀₇ on the leaf having the most evident inhibitory effect. In comparison to the control,the plant height and crown width both decreased by 52.32% and 36.68%,respectively;the stem diameter increased by 97.61%. In terms of application methods,leaf spraying PP₃₃₃ and S₃₃₀₇ had a better dwarfing effect on‘little Anna Rosa’ than pot soil application,whereas pot soil application CCC and B₉ had a better dwarfing effect on‘little Anna Rosa’ than leaf spraying. Various treatments inhibited the leaves of the‘little Anna Rosa’,and the effect was positively related to the concentration. The leaf length,leaf width（excluding 40 mg/L S₃₃₀₇）,and leaf area of the 60 mg/L S₃₃₀₇ treatment were significantly smaller than the control and other treatments（P<0.05）,with reductions of 29.47%,35.44%,and 54.46% respectively,as compare to the control. In terms of application methods,leaf spraying S₃₃₀₇（excluding 20 mg/L）had significantly higher inhibitory effect on leaf length and leaf area than pot soil treatment（P<0.05）. While pot soil treatment of CCC and B₉ had a higher inhibitory effect on leaf length,leaf width,and leaf area of than leaf spraying. Various treatments increased the flower diameter of ‘little Anna Rosa’. The flower diameter of 60 mg/L S₃₃₀₇ was significantly higher than that of the control and other treatments（P<0.05）,which was 65.00% higher than control. In terms of retardants toxicity,high concentrations of PP₃₃₃,CCC and B₉ caused the plants to stop blooming. The S₃₃₀₇,on the other hand,had no toxicity and allowed the plant to bloom normally. 【Conclusion】Leaf spraying with 60 mg/L S₃₃₀₇ boosted the ornamental value of potted Hemerocallis,resulting in a dwarf and compact plant,smaller leaves,dense green foliage,and larger flower diameter.

Key words: Hemerocallis, Plant growth retardants, Dwarfing effects