Pinching Technique Influences Lateral Shoot Development in Poinsettia

Abstract

Lateral shoot growth and plant morphology of poinsettia (Euphorbia pulcherrima Willd.) were influenced by the pinching technique used for apical meristem removal. Plants were pinched in one of four ways: 1) soft (removal of the apical meristem plus stem and leaf tissue associated with leaves ≤2 cm long); 2) medium (removal of the apical meristem plus stem and leaf tissue associated with leaves up to 7 cm long); 3) hard (removal of the apical meristem plus stem and leaf tissue associated with all immature leaves); and 4) leaf removal (LR; soft pinch as defined above plus removal of all immature leaves but not the associated stem tissue). Initial growth of lateral shoots on soft and some medium-pinched plants was less than initial growth of lateral shoots on hard- or LR-pinched plants. Shorter lateral shoots and longer primary stems at anthesis on soft-pinched plants resulted in vertical plant architecture. Hard- and LR-pinched plants had a more horizontal plant architecture. The average height : width ratio of soft-, hard-, and LR-pinched plants at anthesis was 0.77, 0.68, and 0.63, respectively. Of 10 commercial cultivars tested in 1987, 48% of the inflorescences of soft-pinched plants developed below the bract canopy, compared with 27% and 31% for hard- and LR-pinched plants, respectively. These results show that the use of a soft pinch to increase inflorescence number in the bract canopy is not productive if immature leaves are left on the plant when pinching.

Chemical Promotion of Branching and Stem Elongation of Poinsettia

“…This results in a wider and fuller plant, but mechanical pinching is laborintensive and may not be economically feasible in high-density production (Latimer and Whipker 2012). Additionally, pinching in some cultivars can result in poor branching or failure to produce lateral shoots (Faust and Heins 1996), and it can negatively affect flowering, with inflorescences developing below the bract canopy when the pinch is not properly executed (Berghage et al 1989). Cultural practices affecting light (Liu and Heins 2002 Botto 2009), temperature (Berghage and Heins 1991;Faust and Heins 1996), water deficit (Alem et al 2015), and nutrition (Latimer and Whipker 2012;Scoggins and Mills 1998) can also be manipulated to alter vegetative growth rate and branching pattern.…”