Effect of extreme short day treatment (ESD) on the development and appearence of Calibrachoa hybr. Cerv. and Scaevola saligna G. Forst

Greenhouse nurseries struggle with increasing energy costs. An extended use of black-out screens for 18 hours per day in bedding plant production indicates the possibility to decrease energy costs in winter and early spring. Trials carried out with Calibrachoa hybr. ‘Red Million Bells’ and Scaevola saligna ‘Safir’ showed that plants treated with extreme short day (6h, ESD) became more compact and developed a higher number of lateral shoots. Plants of both species were exposed to ESD for a different number of weeks leading to the most compact plants in the treatment with the highest number of weeks in ESD. The more compact plants could be placed denser during the ESD-period (space saving) and ESD made it possible to time the bedding plants to a specific date. The number of floral shoots was significantly higher at anthesis. ESD is a potential tool for timing, growth regulation and energy saving for several pot and bedding plants