Optimizing planting density for cut Helianthus annuus and Zinnia elegans

Abstract

A study was conducted to optimize plant spacing for cut Helianthus annuus cv. Pro Cut Orange and Zinnia elegans cv. Double Super Yoga. Seedlings were raised in 128-celled plastic plug trays containing coco coir, compost and silt (1:1:1; v/v/v) as substrate. At 2-4 true leaf stage, seedlings were transplanted outdoors in thoroughly tilled and leveled flat beds at plant and row spacing of 15.0 × 15.0, 15.0 × 22.5, 22.5 × 22.5, 22.5 × 30.0, or 30.0 × 30.0 cm with plant populations of 40, 26, 17, 13 or 10 plants per m2, respectively. Experiments were laid out in randomized complete block design with three replications individually for each species. Findings revealed that for Helianthus annuus, plants grown at 15.0 × 15.0 cm spacing produced tallest plants with greatest plant canopy diameter. While leaf area, stem diameter and vase life were highest for plants spaced at 30.0 × 30.0 cm. Plant spacing had no effect on number of leaves per plant, fresh weight of stem, flower quality and internodal distance. Similar results were recorded when this experiment was repeated on Helianthus annuus during next year for confirmation of results. In case of Zinnia elegans, plants spaced at 30.0 × 30.0 cm exhibited highest plant canopy diameter, number of leaves per plant and number of flowers per plant, while plants spaced at 15.0 × 15.0 cm had highest plant height and leaf area. Flower diameter, stem diameter, flower quality, internodal distance, fresh weight of a stem and vase life were similar irrespective of plant spacing. Based on the findings, it can be concluded that quality cut Helianthus annuus production was greatly improved when plants were spaced at 15.0 × 15.0 cm, while 30.0 × 30.0 cm spacing was optimal for cut Zinnia elegans production and may be used for commercial cultivation of Helianthus and Zinnia in Punjab.