Effect of plant density on stem and flower quality of single-stem ornamental sunflower genotypes

The aim of this research was to determine the optimum planting density for the production of high-quality cut flowers with desirable characteristics. 25 single-stem ornamental sunflower genotypes were planted at different densities and evaluated for flowering time, flower diameter, and stem circumference and length over a two-year production cycle. Three spacing patterns were used: 25 × 25 cm, 30 × 30 cm, and 70 × 30 cm, which led to the planting densities of 160 000, 90 000, and 60 000 plants/ha, respectively. The plant density had the most important effect on the stem circumference, flower diameter, and stem length (total variation 52, 60, and 58%, AMMI analysis) and a small effect on the flowering time (total variation 1%, AMMI analysis). Based on environment-focused scaling, all high-density environments could be suitable for the production of single-stem sunflower genotypes. The results demonstrated the adaptation of several sunflower genotypes G9, G11, G12, G21, and G22 as the most suitable based on the optimum flower diameter, stem circumference, and stem length. These results may lead to progress in growing ornamental sunflowers as a cut flower.