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Chilling requirements for cherry trees

In a cooperative project of the University of Bonn (INRES Horticultural Science and Center for Development Research (ZEF)), DLR and partners from the World Agroforestry Center (ICRAF), Nairobi, Kenya, the plant physiological functions of the winter chilling requirements of fruit trees are investigated.

Cherry trees

The chilling requirement was determined using the three most common chilling models: Chilling Hours (CH) according to Weinberger 1950, Chill Units (CU) according to Richardson et al. 1974 and Chill Portions (CP) according to Erez et al. 1987.

In the experiments with 160 container trees (three sweet cherry varieties) 8 climatic scenarios were investigated. Sweet cherry, as one of the most affected tree crop by global warming and rising winter temperatures, was used as model crop. The three varieties were selected according to their specific chilling needs (low -500CH-, medium -1.000 CH-, high -1,500 CH- chilling requirement). For instance the widely spread variety ‘Schneiders späte Knorpelkirsche’ with a high chilling requirement up to 1,500 CH was selected. In order to simulate the recent climate change with an average temperature increase of max. 2°C, some of the container trees were placed in an unheated greenhouse.

Partners: Martin Balmer (DLR), Dr Eike Luedeling (ICRAF, Kenia), Prof.  Dr Jens Gebauer (Hochschule Rhein Waal)

Project duration: 2012-2017

Contact: Dr Michael Blanke, E-Mail: mmblanke(at)

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