Deferring Flowering of Two Hybrid Nobile Dendrobium Cultivars by Holding Plants Under Low Temperature After Vernalization

Very few studies have been done to make the year-round greenhouse production of dendrobium orchids possible. This experiment was part of a study to develop a strategy to defer flowering of nobile dendrobium orchids by holding them under low temperature after vernalization. In Sept. 2008, mature Dendrobium Red Emperor ‘Prince’ and Dendrobium Sea Mary ‘Snow King’ plants in 10-cm pots were held in 10 °C growth chambers for various durations after 4 weeks of vernalization. Treatments consisted of five durations of low temperature holding (0, 4, 8, 12 and 16 weeks). Following treatment, plants were moved to a greenhouse. Time to anthesis, node differentiation (including number of flowering nodes, aerial shoots and aborted buds) and flower quality (including flower number, flower diameter, flower number per flowering node, and postharvest flower longevity) were recorded. For both cultivars, with the increase of duration of holding in low temperature, plants needed longer time to reach anthesis from the beginning of low temperature treatment; however, the time to anthesis decreased when the low temperature treatment duration was excluded. Various durations of low temperature holding did not affect the percentage of flowering nodes, aerial shoots or aborted buds for both cultivars. Longer low temperature holding durations resulted in larger flowers in Red Emperor ‘Prince’ but at the same time caused a decrease in the flower number per flowering node for both cultivars. Most flower quality parameters of Sea Mary ‘Snow King’ were not affected by longer low temperature holding durations. Especially, the postharvest flower longevity was not adversely affected by various durations of low temperature treatment, which could make low temperature holding be used commercially to extend the marketing time without reducing the quality of the flowers. However, our data showed that the longer the plants were held in low temperature, the more leaves abscised. This is a potential detrimental effect of low temperature holding.