opulation growth and expanstion of civil life have lead to the reduction of natural vegetatio and increase of air pollution. Therefor, creation of land scape by using various plants for reduction of air pollution and increase of mental tranquillity i necessary. In designing gree land scapes, annual and prennial plant are more important for their colour variation and shapes. Short plants with big flowers are also more valuable. Zinnia and Rudbeckia are example of those plant that have long blooming priod . These plant propagated by seed are high long .Short plants obtained by expensive F1 seeds, show generation depression, so this is necessary to find some ways to regulate height without deteriorating flower quality. Growth retardants are chemical organic componds that slow cell divisio and cell elongation in shoot tissues and regulate plant height. Paclobutrazol and cycocel are two type of these chemical that can control growth and cell elongatio by inhibiting gibberelic acid biosynthesis. This study wa conducted to find out the effect of paclobutrazol and cycocel on some quantitative and qualitative characteristics of Zinnia and Rudbeckia. Plants tralanted at Horticulture Department farm, College of Agriculture, Isfaha University of Tecnology i 2007. Seed of Zinnia and Rudbeckia were sow o plug trays. Seedling tralanted to pot whe plant were approximately 10 centimeter i heigh. Paclobutrazol (5 , 15, 30 mg/L ) and cycocel (500, 1000, 2000 mg/L) were applied as a single foliar spray to run off whe apical flower bud presented i zinnia and whe plant had 8 to 15 true leave i rudbeckia.
