Selecting appropriate planting date and density is one way of organic production of agricultural products and to minimize the use of chemical pesticides. This is very important especially in the case of medicinal plants.Roselle (Hibiscus sabdariffa) is anannual plant of the family Malvaceae.The plant is considered to have antihypertensive properties .Roselle also, has been used in folk medicine as a diuretic, mild laxative, and treatment for cardiac and nerve diseases and cancer. The calyces of plant are rich in anthocyanins, as well as protocatechuic acid. In order to investigate the effect of cultivation data and density on control ofdiseasesof Roselle (Hibiscus sabdariffa), an experiment was conducted atfarmlocated in thecityof Darab, Fars, in 2013. A split-plot layout based onrandomized complete block design with three replications was used. Cultivation data (25March, 15April, and 15May) were allocated to main plots and density (50*50, 50*75 and 50*100 cm) allocated to sub plots. Results showed that cultivation data and density had a significant effect on the incidence of root rot diseases of roselle. The highest rate of root rot in March (61.73%) and lowest rate was observed in April and Mayplanting (31.41% and 31.64%, respectively). Also in 50*50 cm plant spacing the greatest rate of root rotwasobserved (50.24%), but in the third plant spacing (50*100 cm) this the rate of root rot was observwd 26.65%.Inthisstudy, planting date May with plant spacing of 50*100 cm have thelowest rates of diseases.

Keywords