INFLUENCE OF DAYLENGTH AND TEMPERATURE ON GROWTH AND DEVELOPMENT IN POINSETTIA (EUPHORBIA PULCHERRIMA WILLD.)

T. Kristoffersen
Garner and Allard (1963) demonstrated that poinsettia is a short day plant and that the critical daylength is close to 12.5 hours. By natural daylength flowering should therefore occur around Christmas. It has been experienced, however, that the time of flowering may vary considerably, and this has been a great problem in timing the crop in commercial production. Roberts and Struckmeyer indicated in 1938 that there is interaction between daylength and temperature in the flowering of this plant. Post (1949, 1951) and Laurie, Kiplinger and Nelson (1958) stated that temperature above 18°C inhibited flowering. Langhans and Larson (1960) obtained the earliest flowering when the night temperature was 15 to 21°C, and they found only a small effect of day temperature between 10 and 27°C. They concluded, however, that higher night temperature or higher temperature both day and night will result in earlier flowering than low temperature.

During the last years many valuable cultivars have been introduced which have created new enthusiasm for poinsettia. It is of great importance in intensive plant production to be able to time the flowering with great accuracy. Daylength and temperature may be relatively easily adjusted in greenhouses and it is necessary to have exact information about the optimal conditions for the plant at the various stages of development. Since the literature is not conclusive on this point, several experiments have been conducted in order to gain knowledge as to the effect of light, temperature and other cultural factors on growth and development of the new cultivars.

Kristoffersen, T. (1969). INFLUENCE OF DAYLENGTH AND TEMPERATURE ON GROWTH AND DEVELOPMENT IN POINSETTIA (EUPHORBIA PULCHERRIMA WILLD.). Acta Hortic. 14, 79-90
DOI: 10.17660/ActaHortic.1969.14.7
https://doi.org/10.17660/ActaHortic.1969.14.7

Acta Horticulturae