Temperature Regulates Flowering of Two Odontioda Orchid Hybrids

Abstract

The production value of potted orchids has increased by 155% in the past decade, and they are now the second-most valuable potted flowering plant in the United States. Scheduling orchids to flower on specific dates requires knowledge of the environmental parameters that regulate flower induction. However, the flowering requirements of the vast majority of orchid species and hybrids have not been well described. Odontioda is a cool-growing, epiphytic genus originating from the Andes Mountains of South America, and several hybrids are commercially grown for their bright-colored flowers and compact habit. We quantified the promotion of inflorescence initiation and time from visible inflorescence (VI) to anthesis at constant and fluctuating day/night temperatures. Odontioda George McMahon `Fortuna' and Lovely Penguin `Emperor' were grown at constant temperatures of 14, 17, 20, 23, 26, or 29 °C, and day/night (12 h/12 h) temperatures of 20/14, 23/17, 26/14, 26/20, 29/23, or 29/17 °C. Plants were grown in glass greenhouses under a 12-h photoperiod, and shading was provided so that the maximum instantaneous irradiance was ≤300 μmol·m-2·s-1. After 6 weeks at the various temperature setpoints, heat stress symptoms were observed on plants grown at 26, 29, 26/14, 26/20, 29/23, and 29/17 °C. After 14 weeks, ≥60% of both hybrids had VI when grown at 14, 17, 20, or 20/14 °C. Data for time from VI to anthesis were converted to a rate and a thermal-time model relating temperature with inflorescence development was developed. This information could be used by commercial orchid growers to schedule flowering Odontioda orchids for specific market dates.