2018 ASHS Annual Conference

Plant density is critical in the growth and development of specialty cut sunflower (Helianthus annuus L.) cultivars. An experiment was conducted to evaluated four plant spacings; 8 x15, 15 x15, 23 x23, and 30 x 30 cm using three non-branching sunflower cultivars ‘Pro Cut Gold’, ‘Sunrich Lemon’, and ‘Superior Gold’. Stem length, stem diameter, flower diameter disk diameter, days-to-harvest and number of marketable stems were determined at harvest. The 30 x30 spacing resulted in the largest stem diameter, flower diameter, disk diameter, fewest days-to-harvest and higher percentage of marketable stems. Stem length was not significantly different for the other spacings, but tended to increase with plant density. The percentage oof stems that were marketable declined significantly to 54% for the 8 x 15 cm spacing compared to 96% for the 30 x30 cm spacing. While the percentage of marketable stems declined, the number of stems per area increased from 10, 15, 28, and 44 stems m² for the 30 x30, 23 x 23, 15 x 15, and 8 x15 cm spacing, respectively. ‘Superior Gold’ a vigorous cultivar produced marketable stems at all four spacings. ‘Pro Cut Gold’ produced marketable stems at the 23 x23 and 30 x 30 cm spacing and ‘Sunrich Lemon’ failed to produce marketable stems. This initial experiment indicates that increased plant density reduced sunflower size while producing more marketable sunflower stems, however cultivar selection may be critical.