To create year-round landscape designs, it is necessary to consider flowering period of various seasonal flowers in plantings. Seasonal flowers are used in large quantities in urban green spaces during a year. An experiment was conducted in Islamic Azad University of Chaloos during 2010 and 2011 to evaluate the effects of planting dates on flower yield and flowering period of Calendula officinalis, Bellis perennis and Viola sp..Three planting dates (23 September, 23 October and 22 November) were compared in a randomized complete block design experiment with three replications. Result showed that different planting dates can affect number of flowers as well as flowering period of these seasonal flowers. Early planting extended flowering period and resulted in higher numbers of flowers on the three studied plant species. Longer growing periods, February to May, eventually produced a greater number of flowers than shorter growing periods. Based on the results, early planting date (23 September) is recommended due to the fact that the plants can benefit the entire growing season. This can assist the plant species to complete their morphological and physiological cycle, hence, produce the highest flower yield and have longer flowering period.

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