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.
Publications
News
POPLARVILLE, Miss. -- Mississippi blueberry producers expect to see substantial yield losses in the state’s largest commercial fruit crop after the hard freeze that hit the state on the weekend of March 18. Eric Stafne, fruit and nut specialist with the MSU Extension Service, said growers will see significant losses. The condition of the crop is poor based on what commercial growers are reporting to him and his observation of damage to blueberry plants at the South Mississippi Branch Experiment Station in Poplarville, where he is based.
RAYMOND, Miss. -- Producers in Mississippi can provide feedback and input on the agricultural research and educational programs offered by Mississippi State University during the upcoming producer advisory council meetings. Hosted by MSU Extension Service and Mississippi Agricultural and Forestry Experiment Station personnel, the Producer Advisory Council meetings will be held in February. These meetings allow producers to learn about current research and educational opportunities, as well as to communicate their needs in these areas.
HATTIESBURG, Miss. -- The Mississippi State University Extension Service will host two free educational workshops for blueberry growers in January -- one in person and another online.
The in-person workshop will be held Jan. 24 at the MSU Extension Forrest County office at 952 Sullivan Drive in Hattiesburg from 1-4 p.m. The virtual workshop will be Jan. 26 from 2-4 p.m.
Mississippi pecan producers faced a particularly challenging year with drought and then rain at the wrong time, but irrigated orchards are making a good crop.
Eric Stafne, fruit and nut crop specialist with the Mississippi State University Extension Service, said the dry summer did one very good thing: It helped control pecan scab, a disease that is often a problem for the state’s pecan trees.
CARRIERE, Miss. -- Individuals interested in muscadine production can attend an upcoming field day dedicated to the fruit. The 2022 Muscadine Field Day will be held Aug. 25 at the Mississippi State University McNeill Research Unit.
