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Tree Fruit: What are chill hours?

Mississippi's winter chilling information

Deciduous fruits and nuts stop growing in late summer or fall, drop their leaves, go dormant during the winter, and then resume growth in the spring. This relationship between plant and environment is important to the survival of the plant. Growing plants that are non-hardy and incapable of becoming hardy need dormancy during winter for survival. In areas where winters may fluctuate between cold and mild temperatures, species have developed long chilling requirements, so they will not begin to grow in midwinter even though it may warm up to growing temperatures for several days.

Endodormancy (rest) is defined as that period when buds are dormant because of internal physiological blocks that prevent growth even under ideal external conditions for growth. Chilling termperatures above freezing terminate endodormancy. Chilling hours are defined as period of time between 32º F and 45º F. Plants are assigned a certain chilling requirement based on the amount of cold needed to cause 50 percent of the buds to break and flower in the spring. Most blueberries have a chilling requirement of 400-600 hours. Peaches are planted using the chilling requirement as a criteria for variety selection and range from a low of 400 to a high of 1250. Average chilling hours during the winter in Mississippi are: Hattisburg - 400-600; Jackson - 600-800; Mississippi State University - 800-1000; and Holly Springs - 1000-1200.

In 1999, middle to lower Mississippi experienced a low chilling hour accumulation. There is a material (Dormex) that can be sprayed on the commercial plantings that will substitute for about 200 hours. This material is a restricted-use pesticide and can damage the plant if used improperly. Dr. John Braswell, Dr. Frank Matta, and I have asked for, and received, a Mississippi Label for this material.

Dr. Arlie Powell (fruit specialist in Alabama) has performed research and demonstrations with Dormex in Alabama for over 10 years. Information concerning Dormex can be found on their web site, Alabama Winter Chilling

At this time, we feel that we will accumulate sufficient chilling hours in Mississippi. However, some growers may be interested in discussing the use of Dormex in late Febuary.

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Publication Number: P3055
Publication Number: IS1608
Publication Number: P0376

News

Muscadines of various shades are bunched on the vine.
Filed Under: Commercial Fruit and Nuts, Fruit August 8, 2018

Producers can learn about issues related to muscadine production and other fruit-related topics at an upcoming field day in Pearl River County, south of McNeill.

Filed Under: Commercial Fruit and Nuts, Green Industry, Organic Fruit and Vegetables, Other Vegetables, Corn, Cotton, Nuts, Peanuts, Soybeans, Equine, Goats and Sheep, Poultry, Lawn and Garden, Forestry, Seafood Economics, Seafood Harvesting and Processing March 7, 2018

ELLISVILLE, Miss. -- Mississippi State University representatives met with agricultural clients in Ellisville recently to discuss research and education needs for 2018. More than 115 individuals attended this year's event.

A Mississippi State University specialist stands before a room of seated meeting participants.
Filed Under: Commercial Fruit and Nuts, Green Industry, Organic Fruit and Vegetables, Other Vegetables, Nuts, Forages, Beef, Equine, Goats and Sheep, Swine February 26, 2018

Agricultural clients met with Mississippi State University personnel to discuss research and education needs during the annual Producer Advisory Council Meeting for the southwest region February 20.

Filed Under: Commercial Fruit and Nuts January 3, 2018

HATTIESBURG, Miss. -- An afternoon workshop will help Mississippi commercial blueberry growers brush up on the latest research and training related to their crop.

The Mississippi State University Extension Service is hosting the 2018 Mississippi Blueberry Education Workshop Jan. 23 at the Forrest County Extension office in Hattiesburg. Registration is at the door on the day of the event at 1 p.m. There is no cost for the workshop.

Filed Under: Commercial Horticulture, Commercial Fruit and Nuts, Farmers Markets, Greenhouse Tomatoes, Organic Fruit and Vegetables, Other Vegetables August 17, 2017

RAYMOND, Miss. -- Produce growers, packers, industry suppliers and others can learn the requirements of the new federal Produce Safety Rule during one of three upcoming workshops around the state.

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