Kamenetsky, R., Dept. of Ornamental Horticulture, Agric. Research Organization (ARO), Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Barzilay, A., Dept. of Ornamental Horticulture, Agric. Research Organization (ARO), Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Erez, A., Agric. Research Organization (ARO), Volcani Center, Institute of Horticulture, P.O. Box 6, Bet Dagan 50250, Israel
Halevy, A.H., Fac. Agric., Food,/Environ. Qual. S., Department of Horticulture, Hebrew University of Jerusalem, Rehovot 76100, Israel

The temperature requirements of peony during the various stages of its annual growing cycle were studied with the ultimate aim of enhancing early forcing and improving profitability. The immediate objective was to study the effects of chilling and subsequent growth conditions on plant development and flowering of 'Sarah Bernhardt', one of the most popular cultivars of herbaceous peony. Under our experimental conditions, dormancy release was found to be best under chilling regimes of 2°C for 60 days or 6°C for 70 days. Higher temperatures were less effective. Following chilling, the forcing temperature had a major effect on plant development: moderate temperatures of 22/10°C (day/night) were best for enhancing both flowering and stem length; higher temperatures enhanced stem emergence, but reduced stem length and increased flower abortion. High temperatures of 28/22°C (day/night) drastically reduced the percentage of flowers reaching anthesis. Increased temperature in the first period after chilling advanced blooming with relatively minor negative effects on flower development and quality, while high temperature at later stages of flower development promoted flower abortion. © 2002 Elsevier Science B.V. All rights reserved.