How many chilling hours are needed for peach trees to bloom and set fruit?
LOG SHEET RECOMMENDATION: Peach trees need cold weather during the winter for buds to develop properly and so that the trees will bloom and leaf out normally. Chilling requirements refer to the duration and degree of cold needed for a particular variety. There are several methods for estimating the chilling requirements. For this purpose, it is the total number of hours below 45 degrees Fahrenheit that a variety needs during winter for buds to develop normally and bloom. Once chilling occurs, the tree needs a certain amount of warm weather to bloom (about 2 weeks). Varieties with low chilling requirement bloom early and flowers are usually killed by spring frost. Therefore, varieties with a chilling requirement of at least 700 hours are recommended in this area. [1, 2]
From The Bedford Extension MG Help Desk
Editor: Betsy B., Bedford Extension Master Gardener
ADDITIONAL INFORMATION: Peach trees are deciduous and drop their leaves in the Fall and go into a developmental state known as dormancy. As the winter progresses the trees go into another state known as rest, during which they cannot grow even if environmental conditions are favorable for tree growth. Exposure to chilling temperatures is necessary to overcome this period of rest, after which normal bud break and growth can begin once growing conditions are favorable. [2, 5] Varieties can differ greatly in terms of the chilling requirement. Knowing the typical chill hour accumulation of your geographic region should be one of the primary criteria used in choosing cultivars that are suitable to grow there. [2, 3] In this region, typically there is no problem reaching at least 750 chilling hours. 
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