Planting date is the most important factor influencing most physiological and morphological particulars of plant. Proper planting dates cause the created environmental conditions during the days of emergence, settlement and seedling be desirable for plant. Sahel, Siokra and Deltapain cultivares were sowed on 4th of May, 19th of May, 4th of June and 19th of June in a split plot experiment in the form of randomized complete block design, with 4 replications. The main factor included planting dates while the secondery factor included cotton cultivar. Five stages of plant phenology (sowing to 100% emergence, 100%emergence to 50% squaring, 50% squaring to 50% flowering, 50% flowering to 50% bolling and 50% bolling, open bolls) were studied on the basis of number of days and growing degree days (GDD). With delayed planting date the number of needed days from sowing to emergence, emergence to squaring decreased, but the number of needed days from squaring to flowering, flowering to bolling increased. Bolling periods to opening bolls was alike in all planting dates. With delayed planting date GDD decreased from sowing to 100% emergence but in other stages of phenology with delayed planting date GDD increased. Planting dates did not have a significant effect on the number of vegetatives branches and the height of plants but number of fruiting branches were influenced by planting dates so that with delayed planting date the number of fruiting branches increased. Also, there weren’t significant differnces among cultivars for height and fruiting branch number, but for vegetative branch number they were different with Siokra cultivar carrying the most vegetative branches.
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