Effect of planting density and harvest time on flower production from pot marigold (Calendula officinalis L.)

Pot marigold (Calendula officinalis L.) is a medical and aromatic plant used in several pharmacological products due to the bioactive compounds it contains. This study was conducted in Tekirdağ during 2023 to determine the effects of different planting densities and harvest times on the flower production of pot marigold under the ecological conditions of Thrace. The trial was conducted with three replicates in a split-split plot design, with three inter-row (30, 40, 50 cm) and three intra-row distances (10, 20, 30 cm). Flower harvesting was performed weekly over 14 periods. According to the results, planting density had a statistically significant effect on flower yield. The highest number of flowers per plant (4.64-9.22 flowers plant-1), fresh weight of flowers per plant (2.37-5.61 g plant-1), and dry weight of flowers per plant (0.50-1.17 g plant-1) were obtained with 50 × 30 cm planting density in the 12th harvest period. The lowest values were obtained at a planting density of 30 × 10 cm during the 1st harvest period. In the trial, the best fresh (374.3-790.0 kg ha-1) and dry flower (78.7-167.3 kg ha-1) yield values per hectare were obtained from 30 × 10 cm planting density in the 12th and 14th harvest periods. Considering the total flower yields obtained in this one-year study, a planting density of 30 × 10 cm showed promising results for fresh and dry flower yields under Thrace conditions.