Pinching Ornamental Sunflowers Increases Cut Stem Yield and Reduces Flower Size

Abstract

Most sunflower cultivars (Helianthus annuus) grown as cut flowers produce single stems and do not form branches. If pinched (i.e., apical meristem removed) in the seedling stage, plants form branches from basal nodes. In four experiments conducted under field conditions, pinching seedlings increased the number of marketable sunflower stems per plant 2.6 to 4.6 times, but the flowers formed were reduced in diameter by 43%, and flowering was delayed by 1 week to 10 days. Leaving six instead of four basal nodes after pinching only increased stem yield slightly in 2005 but not in 2006. Increasing the space available per plant from 9 × 9 to 12 × 12 inches increased flower diameter of pinched and control plants from 7 to 7.9 cm, but the resulting lower yield per unit area reduced overall value. In three out of four experiments, ‘Procut Orange’ produced more stems after pinching than ‘Sunrich Orange’. Pinching nonbranching sunflowers is a promising technique, increasing yield by a factor of three, and the value of the harvested flowers by 82%.