Regulating planting time under a congenial growing environment could improve growth, flowering and yield as well and thus the quality of crop production. A field experiment was carried out to identify appropriate planting time and growing conditions for flower regulation in marigolds (Tagetes erecta L.) in factorial randomized block design with 5 different planting dates, under open and naturally ventilated polyhouse conditions in two marigold cultivars (cv (s).), ‘Pusa Narangi Gainda’ and ‘Pusa Basanti Gainda’. It was noted that planting dates, growing environments and varieties had significant effects on growth and flowering parameters. Results showed that the 10th of July planting under naturally ventilated polyhouse condition using marigold cv. ‘Pusa Narangi Gainda’ exhibited luxuriant vegetative growth, which ultimately resulted in enhanced flower yield per plant (730.43 g) and per square meter (6.89 kg) with a greater benefit-to-cost ratio (2.86) and hence, was found economically best for commercial production of marigold. However, economic flower yield was also obtained under naturally ventilated polyhouse conditions till August planting.