Abstract: In order to control plant height of pyrethrum (Tanacetum cinerariifolium),B₉,CCC,PP₃₃₃,S₃₃₀₇ with different concentration levels were applied and compared by foliar sprays on the potted plant.Results showed that all the four plant growth retardants had dwarfing effects on plant height with different extent as well as on inhibiting plant crown width.The dwarfing effects and negative effects on plant growth were S₃₃₀₇,PP₃₃₃,CCC,B₉ from strong to weak.The optimum dwarfing treatment for pyrethrum was the application of 200mg/L B9.It not only reduced the height of potted plants to about 30% of that of the control plants,but also inhibited the leaf development and plant width of potted plants,the width of the plant was about 70% of the control plant,and the treated plant was short,compact and suitable for pot culture.

Key words: pyrethrum (Tanacetum cinerariifolium), B₉, CCC, PP₃₃₃, S₃₃₀₇, dwarfing