Poinsettia, Euphorbia pulcherrima is a very lovely plant due to its red and attractive bract colours. It is the most popular decorative plant for Christmas and New Year. Poinsettias have a good market potential as potted flowering plants.
Poor plant quality may result from crowding, poor light, pest and disease problem, and poor scheduling. Scheduling poinsettia is complicated by the interaction of daylength, temperature and cultivar on lateral growth and floral development ( Larson & Langhans, 1963 ).
The removal of shoot apexes to overcome apical dominance and to promote lateral shoot development is referred to as pinching ( Larson 1985 ). In areas with good light, much more latitude may be allowed in time and type of pinching. Suggested pinch dates for Christmas crops vary somewhat with the area from which the information comes ( Pertuit, 1973 ; Tayama et al, 1975 ; Tayama 1978 ).
Pinched potted plants are more floriferous and shorter than single stem plants. Timing a pinch can also affect plant quality. Pinching too early can result in plants that are too tall, and pinching too late can reslut in plants too short. Therefore, pinching, as part of the poinsettia production cultural practices, is done to overcome the apical dominance in order to produce a better quality plant.
Source : Pertanika J.Trop. Agric. Sci. 26(1):15-18(2003)