KClO3 applications affect Phalaenopsis orchid flowering

Potassium chlorate (KClO3) treatments are known to promote flowering in longan plants. Potential effects of KClO3 on Phalaenopsis orchid flowering were investigated in the present study. However, increasing application concentrations of 2, 4, 8 and 16 mmol/L KClO3 delayed spike emergence by 5, 6, 18 and 26 days, respectively. Moreover, they reduced final spike length by 2.1%, 4.0%, 16.2% and 46.1%, respectively. Nonetheless, application of KClO3 at 4 and 8 mmol/L advanced the time to appearance of the first open flower by 13 and 24 days, respectively. Use of 8 mmol/L KClO3 also increased the number of floral buds by 16%. Treatments with KClO3 tended to reduce flower size. Overall, the data suggest that application of KClO3 at an appropriate concentration (e.g. 8 mmol/L) can increase the number of floral buds and advance the time to Phalaenopsis orchid flowering, but may reduce flower size.