Effects of Cooling Temperature and Duration on Flowering of the Nobile Dendrobium Orchid

Abstract

The effects of cooling temperature [constant (10, 13, 15, or 18 °C, or 15, 18, or 21 °C)] and duration (2, 3, 4, 5, or 6 weeks, or 3, 4, 5, 6, or 7 weeks) at two separate locations (College Station and Weslaco, TX) on growth and flowering of Dendrobium Sea Mary ‘Snow King’, a Dendrobium nobile Lindl. hybrid, were investigated and the cooling requirement for flowering was quantified. Interactions between temperature and cooling duration were significant on time required to reach anthesis from either the beginning or completion of cooling, average flower number per flowering node, and percentage of nodes with aborted buds. Increasing cooling duration from 2 to 6 or 3 to 7 weeks resulted in less time to reach anthesis after the completion of cooling. However, the increased cooling durations extended the time needed for producing a flowering crop. Plants cooled at a relatively higher temperature among 10, 13, and 15 °C required less time to reach anthesis after the completion of cooling. Plants had more flowering nodes and total flowers when cooled at 10, 13, or 15 °C than at 18 °C in College Station or at 15 or 18 °C than at 21 °C in Weslaco. The results suggest that 3 weeks at 13 °C has saturated the cooling requirement, and 3 weeks at 13 or 15 °C is a recommended cooling treatment that saves production cost without retarding flower development.