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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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Publications

Publication Number: P3055
Publication Number: IS1608
Publication Number: P0376
Publication Number: IS1445

News

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.

Filed Under: Commercial Fruit and Nuts, Fruit August 4, 2017

STARKVILLE, Miss. -- A group interested in learning more about the ancient and popular art of winemaking will attend an upcoming workshop on the topic Sept. 15 at Mississippi State University.

The Growing, Making and Improving Wines Workshop will be at the A.B. McKay Food Research and Enology Laboratory on the MSU campus. The MSU Extension Service and the Mississippi Agricultural and Forestry Experiment Station are offering the daylong workshop.

Filed Under: Commercial Fruit and Nuts, Fruit August 4, 2017

MCNEILL, Miss. -- Mississippi State University invites muscadine grape growers and those interested in growing these vines to an Aug. 26 field day in Pearl River County.

Topics for the annual Muscadine Field Day include pests, new varieties and vine management. MSU Extension Service, Mississippi Agricultural and Forestry Experiment Station, and U.S. Department of Agriculture - Agricultural Research Service personnel will speak.

Natasha Haynes, Mississippi State University Extension agent in Rankin County, advocates choosing one local ingredient to spotlight in a menu, such as this squash growing at the Southern Heritage Garden at the Vicksburg National Military Park on June 13, 2017. (Photo by MSU Extension Service/Bonnie Coblentz)
Filed Under: Commercial Fruit and Nuts, Farmers Markets, Agri-tourism, Food, Nutrition July 12, 2017

VICKSBURG, Miss. -- Foods grown on Southern farms should end up on Southern tables, especially when those tables are in the state’s many historic bed-and-breakfasts.

That was the message Mississippi State University Extension Service personnel sent home with participants in a recent workshop.

“Nobody wants to go to a Southern B&B and not experience the food, so think about serving local foods,” said Brent Fountain, Extension nutrition specialist.

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