Pinching Sunflowers Produces More Stems—What About Profits?

The technique of pinching out the tops of seedling sunflowers can triple the yield of stems, as seen in summaries of our experiments with single stem and branching varieties in past issues of the Quarterly (Summer 2008 and Winter 2012). We pinched sunflowers in six years of trials, and came to the following major conclusions:
1.    When pinched in the seedling stage (photo), sunflowers increase yield up to 3 to 4 times.
2.    Pinching works on single stem and branched varieties, but branched cultivars produce more side shoots.
3.    Late pinching (before flowering but when flower buds are visible) on single stem varieties produces very short branches, or none at all; on branched varieties many short branches are formed. Pinch as early as possible!
4.    We have not found a good way to mechanize the pinching process.
5.    Pinching stimulates the plants to form several stems in the same physical area, so flower size is reduced. If pinching and close spacing are combined, flowers produced are very small, but yields can reach 10 stems per square foot.
6.    If the plants were too crowded, they produced flowers smaller than 1.5 in., abnormal flower shapes, and thin stems and lodging became common.  

But can you make money with daisy-sized sunflowers? To answer that question, I consulted the USDA cut flower terminal market price list [http://www.ams.usda.gov/mnreports/bh.fx201.txt] and applied the prices to the yields and flower size information obtained in some of our experiments. More specifically, I set a minimum acceptable size disk diameter of 1.5 inches (ignoring petals), below which the value would be zero. I set a value of $0.85/stem for flowers of disk diameter 1.5 to 2.4 inches, $1.00 for flowers of 2.4 to 3.1 inches, and $1.50 for flowers larger than that.

When the yield, price, and flower size information was combined for one of the pinching experiments using the single stem varieties, ‘Procut Orange’ and ‘Sunrich Orange’,  value of flowers per unit land area declined as flower size increased (see Graph 1). In other words, pinching increased yields of small flowers, and increased income. There are practical limits, however. In another experiment with the branching variety ‘Goldrush’, the plant density became so high that flower disk size decreased below 1.5 inches, and value dropped to zero (left side of Graph 2). The differences in flower values between the two graphs are based on land area calculation differences, and should be ignored.
    
So pinch away to profits, but don’t get greedy!

Chris Wien

Professor

Chris Wien is recently retired Professor of Horticulture at Cornell University. Contact him at [email protected]