The influences of irradiance level, day length, temperature, and leaf area on growth and flowering of Zantedeschia elliottiana Engl. W. Wats (yellow calla lily) and Z. rehmannii (pink calla lily) were determined. Plants grown with 45% or 15% of natural irradiance were taller than those grown under full natural irradiance but flowered at the same time and produced a similar number of flowers. Leaf removal treatments had no effect on any characteristic measured. Plants grown with a night interruption (NI; 2200 hr to 0200 hr) were taller than those under short days (SD = 8 hours), but flowered at the same time and produced a similar number of flowers. Plants were grown with air at 15 or 20C in combination with medium temperatures at ambient level (1C less than air temperature) or a constant 20 or 25C. Z. rehmannii grown with the medium at 20 or 25C and air at 1.5 or 20C flowered faster and were taller than plants grown with air at 15C and with the medium at ambient temperature, but plants from all temperatures produced the same number of flowers over a 120-day cycle. When plants grown with a NI in the first cycle were replanted and grown through a second cycle, they were taller than plants grown from SD treatment first-cycle plants. No first growth-cycle treatment influenced flowering in the second growth cycle.
A laboratory incubator equipped with facilities to automatically simulate natural irradiance
