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.
WAYNESBORO, Miss. -- The demand for fresh Mississippi blueberries may grow this year after a mid-March freeze hampered production in neighboring states.
Freezing temperatures during the crop's early growth stage on farms east of the state, especially in Georgia and North Carolina, caused production losses of up to 50 percent.
Meanwhile, 85 percent of Mississippi's blueberry crop was either in good or excellent condition as of May 15, according to a weekly crop progress and condition report published by the U.S. Department of Agriculture.
RAYMOND, Miss. -- This year's early spring temperatures allowed some fruit and vegetable growers to plant their crops a little earlier than usual.
Jeremy Maness, Mississippi State University Extension agent in Smith County, said growers in his county have not experienced any problems so far despite a late freeze.
"Everything is going well," he said. "Tomatoes grown in greenhouses or high tunnels are ready now. We project watermelons will be ready around mid- to late June, and field tomatoes should be ready to start coming off the vine around the first week of June."
RAYMOND, Miss. -- Growers interested in commercial pecan production are invited to a spring field day May 11 in Raymond.
The event will begin at the Mississippi State University Central Mississippi Research and Extension Center at 1320 Seven Springs Road in Raymond. It is hosted by the Mississippi Pecan Growers Association, MSU Extension Service, and Mississippi Agricultural and Forestry Experiment Station.
STARKVILLE, Miss. -- Growing conditions first helped but then hurt Mississippi strawberries this year as the 2017 harvest season comes to an early conclusion.
Eric Stafne, fruit crops specialist with the Mississippi State University Extension Service, said a mild fall and winter helped the crop mature a little earlier than normal.
WOODVILLE, Miss. -- Farmers market and cottage industry sales are a significant part of the Mississippi food scene, and Mississippi State University Extension Service training is helping entrepreneurs take advantage of these business opportunities.
The MSU Extension Service and Department of Food Science, Nutrition and Health Promotion offers training on acidified canned foods and general food safety at locations across the state. An upcoming workshop will be held April 25 in Woodville, Mississippi, at the J.R. Hamilton Extension Building.