Abstract

Blue Vanda hybrids, including Vanda ‘Pakchong Blue’, frequently fail to flower during Thailand’s hot season (March–May), resulting in reduced market supply despite strong commercial demand. This study investigated flowering behavior and the effects of temperature management on growth, flowering, and flower quality of Vanda ‘Pakchong Blue’. In the first experiment, flowering behavior was examined through weekly histological observations of plants maintained under high-temperature conditions following inflorescence removal. Floral buds were initiated under high temperatures but failed to complete development and subsequently aborted. The period from floral initiation to anthesis was approximately 75 days. In the second experiment, plants were subjected to low-temperature treatments (18 ± 2 °C) for 0, 4, or 6 weeks and subsequently transferred to either an evaporative-cooling greenhouse (ECG) or a shaded greenhouse (SG). Plants grown in the ECG flowered during the off-season (March–May), whereas those grown in the SG flowered during the natural flowering season (August–September). Flowering in the ECG occurred 136–156 days earlier than in the SG and produced superior flower quality, including longer inflorescences and a greater number of florets. Exposure to 18 °C for 4 and 6 weeks delayed flowering by 24 and 45 days, respectively, but had no significant effect on vegetative growth. These findings demonstrate that successful off-season flowering and improved flower quality were primarily associated with cultivation in the evaporative-cooling greenhouse, whereas prolonged exposure to 18 °C delayed flowering without affecting vegetative growth. This study provides the first detailed characterization of floral bud development and flowering responses to different temperature-management strategies in this cultivar and highlights the potential of evaporative-cooling greenhouse technology for sustainable orchid production, climate-resilient floriculture systems, and year-round supply of high-quality flowers under tropical conditions.

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