Effects of Day Length and Temperature on Growth and Development of Vanda ‘Pakchong Blue’

Abstract

The demand for orchids, both domestically and internationally, is consistently high throughout the year. However, the production of Vanda orchids, particularly the hybrid Vanda ‘Pakchong Blue’, is still challenging in the summer season when the market demand is high. This research aimed to study the effects of day length and temperature on vegetative growth and flowering regulation during the summer season. The plants were subjected to two different factors: two levels of day length conditions, day length about 12 hours and short-day length of 7 hours (Factor 1); and two levels of cultivation temperature, 30±2°C in a 50% shading greenhouse (Factor 2), and 25±2 °C in an evaporative cooling greenhouse (4 treatments: ND+SG, ND+ECG, SD+SG, SD+ECG). The plants received the same light intensity, averaging 350 µmol m^-² s^-1. The experimental results showed that different day length and temperature conditions had no significant effects on vegetative growth parameters, including plant height, leaf length, and number of leaves throughout the experiment. However, the experimental treatments resulted in statistically significant differences in flowering response. Providing the Vanda ‘Pakchong Blue’ with short-day conditions delayed the flowering compared with a 12-hour day length Additionally, growing the orchids in an evaporative cooling greenhouse significantly improved flower quality and flowering efficiency, with a higher blooming percentage and a longer flower spike lifespan compared with those grown in the 50% shading greenhouse.