The practice of removing an herbaceous plant’s growing point (commonly termed pinching or topping) has been used for many centuries to affect growth, plant productivity, or shape (Escher, 1996; Hunt, 1893). Most commonly, pinching is used to reduce plant height and encourage branching (Faust, 2006). When used on cut flower species that typically only produce a single flower, pinching during the early vegetative stage, allows a multibranched plant to develop (Badge et al., 2014; Cheong et al., 2002; De Pascale et al., 2005).
Pinching has been practiced on many annual species used as cut flowers, including gypsophila [Gypsophila paniculata (Cheong et al., 2002)], lisianthus [Eustoma grandiflorum (De Pascale et al., 2005)], and african marigold [Tagetes erecta (Badge et al., 2014)]. In herbaceous perennials such as delphinium (Delphinium elatum) pinching of early shoots breaks apical dominance to encourage growth of secondary shoots (Garner et al., 1997). Although pinching of sunflowers is apparently widely practiced (Armitage and Laushman, 2003; Dole and Wilkins, 2005), scientific study of this topic has been limited. A 1-year study in Mississippi determined that pinching increased yield of branching more than nonbranching cultivars, but did not manipulate spacing nor include a nonpinched control treatment (Sloan and Harkness, 2010). The research presented here documents the effects of pinching and plant spacing on productivity and cut flower characteristics of two unbranched cultivars of sunflower.
ArmitageA.M.LaushmanJ.M.2003Specialty cut flowers. 2nd ed. Timber Press Portland OR
BadgeS.PanchbhaiD.M.DodV.N.2014Response of pinching and foliar application of gibberellic acid on growth and flower yield in summer African marigoldRes. Crops15394397
CheongD.C.JeongJ.S.ChoiJ.S.ParkH.B.2002Effect of planting date and pinching on flowering and cut flower yield of Gypsophila paniculata in subalpine areasJ. Korean Soc. Hort. Sci.43773776
De PascaleS.Di MuccioP.FiorenzaS.ParadisoR.2005Effect of the planting density, pinching and illumination on flowering of lisianthusColture Protette34117784
DoleJ.M.WilkinsH.F.2005Floriculture principles and species. Pearson Prentice Hall Upper Saddle River NJ
EscherF.1996Schnittblumenkulturen. 4th ed. Verlag Eugen Ulmer Stuttgart Germany
HuntM.A.1893How to grow cut flowers. Moore and Langen Terra Haute IN
MajidH.R.SchneiterA.A.1987Yield and quality of semidwarf and standard-height sunflower hybrids grown at five plant populationsAgron. J.79681684
RobinsonR.G.FordJ.H.LueschenW.E.RabasD.L.SmithL.J.WarnesD.D.WiersmaJ.W.1980Response of sunflower to plant populationAgron. J.72869871
SloanR.C.HarknessS.S.2010Planting date and pinch treatments affect growth of field-grown cut flower sunflower cultivars. Mississippi Agr. For. Expt. Sta. Bul. 1180
U.S. Department of Agriculture (USDA)2016Boston ornamental terminal prices. 23 Mar. 2016. <http://www.ams.usda.gov/mnreports/bh.fx201.txt>
YamaguchiN.GotoT.KobikiK.2014Effect of minimum air temperature on occurrence of abnormal inflorescence and cut flower quality in Gypsophila paniculata ‘Altair’Hort. Res.13161167