Temperature Effects on Flower Induction of Two Phalaenopsis Orchid Hybrids

Abstract

The commercial production of potted flowering orchids has increased tremendously in the past decade, and is now the second most valuable potted flowering crop in the United States. Phalaenopsis spp. comprise a large percentage (75% to 85%) of the potted orchid sales in the U.S. due to their long flower life and ease of scheduling to meet specific market dates. Constant air temperatures above ≈26 °C inhibit flowering of most Phalaenopsis hybrids, and a 25/20 °C day/night temperature regimen is used commercially to induce flowering. However, the relative promotion of flowering by constant versus fluctuating day/night cool temperatures (<25 °C) has not been well described. Phalaenopsis Miva Smartissimo × Canberra `450' and Brother Goldsmith `720' were grown at constant temperatures of 14, 17, 20, 23, 26, and 29 °C, and day/night temperatures of 20/14, 23/17, 26/14, 26/20, 29/23, and 29/17 °C;. Plants were grown in glass greenhouses with a constant photoperiod of 12 h, and shading was provided so that the maximum instantaneous irradiance was ≤150 μmol·m-2·s-1. After 6 weeks at the various temperature setpoints, ≥80% of plants of both cultivars had VI when grown at a constant 17, 20, or 23 °C, and at the 23/17 °C day/night regimen. None of the plants were reproductive within 6 weeks when grown at a constant 26 or 29 °C, or at the 26/14, 26/20, 29/17, or 29/23 °C day/night temperature setpoints. Therefore, temperature during the day and night both influence flowering of these two Phalaenopsis orchid hybrids.