The delay in flowering by 16 d when plants were grown atND + 14HID as compared to reduced irradiances between May and September may have been due to naturally high seasonal irradiance. Maintaining light levels at 2000–3000 ft-c and extra shade beginning in mid-March (South) or early April (North) to reduce light intensity was suggested for gloxinia (Aulenbach, 2009),requiring up to 60% shade depending on the greenhouse cover material. Reducing irradiance level will also lower the greenhouse temperature, an additional benefit during the summer season. It is suggested that S. cardinalis be grown under a natural irradiance between November and February, when irradiance could be easily maintained between 10 and 48 W/m2.