The 2012 ASHS Annual Conference

This study was conducted in a commercial greenhouse to examine the effects of summer cooling control during forcing culture of Cymbidium ‘Red Fire’ and ‘Yokihi’, which included night interruption (NI) in winter. The greenhouse was divided into two sections for separate cooling control during the long day summer season. One section was cooled by a mist system (Mist), while the other was cooled by a shade screen (Shade). During short day season, the plants were grown with NI with low light intensity (LNI) of 3–7 µmol·m^-2·s^-1 or high light intensity NI (HNI) of 120 µmo·m^-2·s^-1 for four hours (22:00–02:00 h), whereas the control plants were grown under natural short day condition. Summer cooling for 9 weeks and winter night interruption for 16 weeks were employed twice during the experimental period of two years. Day temperature was approximately 2 °C lower in the Mist than Shade, while the relative humidity of the Mist and Shade was 80 ± 5% and 55 ± 5%, respectively. The daily light integral of the Shade compartment was only 48% that of the Mist condition. The time to flowering pseudobulb emergence from initial planting for ‘Red Fire’ and ‘Yokihi’ was reduced by LNI and HNI regardless of the cooling treatments but the promotion effect was more in the Mist condition than the Shade. Leaf number and pseudobulb diameter increased more in the Mist condition than in Shade after 1 year cooling treatment. The plants that received NI followed by Mist condition flowered within two years, however, none of the plants flowered under the Shade condition. The time to flowering of the plants decreased and the number of flowers increased more in HNI than in LNI group. Cymbidium ‘Red Fire’ and ‘Yokihi’ could reach flowering within two years by summer cooling with Mist and winter forcing by NI treatment.