Plants can be kept vegetative by growing them at a temperature above 26 degsC because Phalaenopsis forms flowers only when grown for some weeks at a temperature lower than this. Once the vegetative plants are big enough, the air temperature can be dropped to a temperature that will encourage flower formation.
Recent research has demonstrated that flowering is controlled by the day temperature rather than the night temperature. Therefore the experiments reported here tested whether the day temperature had to be maintained above 26 degsC throughout the day period.
Plants of three clones of Phalaenopsis and one of Doritaenopsis were grown at constant temperatures of 20 degsC or 29 degsC. Other plants were grown at a basic temperature of 20 degsC, which was raised to 29 degsC for four, eight or 12 hours around the middle of each 16-hour day.
Flower formation was suppressed in Phalaenopsis 'Mosella' and 'Explosion', and was delayed in Phalaenopsis 'Golden Treasure' and Doritaenopsis 'Newberry Parfait' when the temperature was raised for 12 hours each day. This treatment would save energy, but it should probably be used only with the more responsive clones.
High-temperature Inhibition of Flowering of Phalaenopsis and Doritaenopsis Orchids by Newton and Runkle (2009). HortScience 44 (5): 1271-1276. Members of ISHS can view HortScience from the website, www.ishs.org.