Plant size at flower induction affects flowering of Phalaenopsis orchids

The aim of the study was to evaluate the effect of different plant sizes at the phase of flower induction on flowering time and inflorescence characteristics in 3 Phalaenopsis hybrids, ‘Sogo Yukidian’ (large flower), ‘Chain Xen Diamond’ (medium flower) and ‘Pinlong Cheris’ (small flower), grown in pots in a heated glasshouse The following treatments were compared: the optimal size, corresponding to 5 leaves/plant in the Large and Small hybrids and 7 leaves/plant in the Medium one; and a sub-optimal size, corresponding to 2 leaves less than the optimal one (3 and 5 leaves/plant, respectively). Thermal treatment for flower induction was performed by moving plants from the compartment for vegetative growth (28/26 °C, day/night) to cooler temperatures (21/19 °C) for 8 weeks. In all the hybrids, premature exposure to inductive treatment delayed the beginning of flowering and significantly reduced the inflorescence quality parameters, with different effects in the different hybrids. These results confirmed that a critical size is required to optimize flowering performance of Phalaenopsis, however, from a commercial point of view, the convenience of early flowering and energy savings achievable by shortening the vegetative phase, could, in some situations, outweigh the benefits of producing higher quality Phalaenopsis.