Cohen, D., Department of Ornamental Horticulture, Institute of Plant Sciences, Volcani Center, Bet-Dagan 50250, Israel, Robert H. Smith Institute of Plant Science and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel
Ziv, D., Department of Ornamental Horticulture, Institute of Plant Sciences, Volcani Center, Bet-Dagan 50250, Israel
Fintea, C., Department of Ornamental Horticulture, Institute of Plant Sciences, Volcani Center, Bet-Dagan 50250, Israel
Ion, A., Department of Ornamental Horticulture, Institute of Plant Sciences, Volcani Center, Bet-Dagan 50250, Israel
Forer, I., Department of Ornamental Horticulture, Institute of Plant Sciences, Volcani Center, Bet-Dagan 50250, Israel
Rabinowitch, H., Robert H. Smith Institute of Plant Science and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel
Kamenetsky, R., Department of Ornamental Horticulture, Institute of Plant Sciences, Volcani Center, Bet-Dagan 50250, Israel

Paperwhite Narcissus of the Tazetta group is one of the most important flower crops in Israel, with more then 20 million bulbs exported annually for both dry sales and flower production. Recent releases by The Volcani Center (Agricultural Research Organization) of cvs. 'Ariel' and 'Inbal', require adequate protocols for flowering manipulation and extending blooming prior to December and after January, as is common under ambient conditions in Israel. Flowering physiology, including intrabulb flower development, storage, and forcing methods of the new cultivars, were studied in comparison with cv. 'Ziva'. For September 1 and October 15 planting, bulb storage under ambient conditions (open shed) or at 25 °C was followed by two weeks of chilling at 13 or 9 °C. Post-harvest storage at 25 °C enhanced intrabulb flower differentiation, and pre-planting chilling promoted intrabulb scape elongation, but scapes' final length were shorter then in the control. For January 1 planting, bulbs were kept at 30 °C with a consequent delay in intrabulb flower differentiation. A two-week chilling at 17, 13, or 9 °C resulted in a shorter period from planting to bloom. Early and late plantings resulted in a smaller number of flowers per inflorescence, as compared with planting on October 15. The information presented may serve for devising useful forcing protocols for quality production of N. tazetta flowers. © 2009 Science From Israel/LPPLtd.