Inhibition of Premature Flowering of Phalaenopsis Orchids by High Temperature Interruption

This study was conducted to determine the premature flowering inhibition of Phalaenopsis plants by high temperature interruption. Eight-month-old young Phalaenopsis ‘Hwasu 355’ and Doritaenopsis ‘Mantefon’ plants were treated with four different temperature treatments: continuous low temperature (no interruption), 1 week of high temperature every 1 week of low temperature, 1 week of high temperature every 2 weeks of low temperature, and 2 weeks of high temperature every 2 weeks of low temperature. The low temperature and high temperature were set at 25/20 °C and 28/28 °C, respectively, and maintained for 16 weeks. In ‘Hwasu 355’, flower-stalks of all plants grown at no interruption conditions emerged, whereas flower-stalk emergence of plants treated with high temperature interruption was not observed. However, ‘Mantefon’ plants showed flower-stalk emergence in all treatments. The percentage of visible inflorescence (flower-stalk longer than 0.5 cm) increased with increasing the interval between high temperature interruptions. The number of days to visible inflorescence was increased with increasing total high temperature duration during cultivation. These results suggest the possibility of using high temperature insertion during relatively low temperature cultivation in winter to prevent premature flowering and to save the heating cost. However, since ‘Mantefon’ plants were more sensitive to low temperature and showed flower-stalk emergence in all interruption treatments, the modification of interruption method is needed in order to inhibit premature flowering more effectively.