Response of growth and yield of Stevia (Stevia rebaudiana Bertoni) to planting space and harvesting time

In order to investigate the effect of harvesting time (17 August and 17 September) and planting space (20, 25, 30 and 35 × 50 cm) on growth criteria, quantitative and qualitative yield of Stevia rebaudiana Bertoni, a factorial experiment based on randomized complete block design with three replications was carried out in Research Station of Department of Horticultural Science and Landscape Engineering, University of Tehran during years of 2013-2014. Based on results, planting space significantly affected the most measured traits except plant height, leaf to stem ratio and chlorophyll content. By decreasing of planting space from 35×50 to 20×50 cm, fresh and dry weight of the aerial part and leaf and yield of Stevioside and Rebaudioside A were increased. Also, harvesting time significantly affected the measured traits except chlorophyll content in which the highest plant height and diameter, fresh and dry weight of the aerial part and yield of Stevioside and Rebaudioside A were obtained at 17 September. Harvesting at 17 August caused the highest leaf to stem ratio. The interaction effect of planting space and harvesting time significantly affected leaf dry weight in which the highest leaf dry weight obtained by the planting space 20×50 cm and 25×50 cm at 17 September. There was no significant effect on chlorophyll content. In general, based on these results, planting space of 20 and 25 × 50 cm and harvesting time at 17 September compared to other treatments pronounced better for cultivation of Stevia in studied area of Karaj.