OPTIMIZING BORON APPLICATION FOR IMPROVED GROWTH, FLOWERING, AND FLORAL QUALITY OF ORNAMENTAL SUNFLOWER (HELIANTHUS ANNUUS L.)

Abstract

Boron is an important micronutrient involved in cell-wall development, reproductive growth, and flowering, but its application rate can strongly influence ornamental crop performance. The present study evaluated the effects of boron application on the germination, vegetative growth, flowering, and floral characteristics of ornamental sunflower (Red) under greenhouse conditions at Lasbela University of Agriculture, Water and Marine Sciences, Uthal, Balochistan, during the 2025 growing season. The experiment was arranged in a completely randomized design with three replications and four treatments: T0 (control), T1 (6 mL boron), T2 (12 mL boron), and T3 (18 mL boron). Data were recorded for germination percentage, leaves per plant, plant height, stem diameter, flowers per plant, days to flower initiation, flower diameter, fresh and dry flower weight, flower stalk length, and number of side branches. Boron application markedly improved most measured traits, with T2 generally producing the strongest overall response. Germination increased from 6.10% in the control to 12.17% under T2. T2 also produced the highest number of leaves (28.00 plant⁻¹), greatest plant height (131.30 cm), stem diameter (3.30 cm), flowers per plant (3.13), flower diameter (17.43 cm), fresh flower weight (152.87 g), and dry flower weight (65.13 g). T3 produced the longest flower stalks (48.37 cm), but also substantially delayed flower initiation (65.67 days). Overall, the results indicate that a moderate boron application of 12 mL was most effective for improving vegetative growth, flower development, and floral biomass of ornamental sunflower under the tested greenhouse conditions, whereas higher application did not consistently provide additional benefits.