Troup extension agent: Winter warm spells are not so peachy for some fruits
Published 12:00 am Friday, February 19, 2016
Warm spells in the middle of winter can be a cause for concern. There are news reports about the danger of warm weather spoiling our peach and blueberry crops.
Ideally, having the temperatures remain constantly low throughout the winter would alleviate a lot of these fears. Weather, as we know, is anything but constant or predictable.
Besides affecting our sinuses, how does these warm and cold spells affect our fruit production? Stone fruits also known as drupes develop a fleshy part around a hard stone or pit. Some of the members of the genus prunus are peaches, plums, nectarines, cherries and apricots.
These stone fruit trees develop their vegetative and fruiting buds in the summer. In response to shorter day lengths as winter approaches, these developed buds go dormant. Once dormancy sets in, freezing temperatures and mid-winter warm spells will not bother them.
When the buds have accumulated enough chilling units of cold weather they will break their dormancy. If there are enough chilling units, flower and leaf buds will develop normally.
UGA categorizes peach varieties by their chill requirement hours. A low chill variety needs less than 600 hours; moderate needs 600 to 750 chill hours and high requires 750 to 900 hours. You can probably guess which category the best tasting varieties fall into.
If there are not enough chilling units during the winter bad things begin to happen. The first sign is that foliation — leafing out — will be delayed. There will be small tufts of leaves near the tips of the branches and none below the tips for 12 to 20 inches.
You may also see heavy suckering from the lower parts of the tree. Because full foliation is delayed, fruit set is reduced and the tree is weakened.
Because bloom is delayed in response to insufficient chilling, and abnormalities in pistil and pollen development appear, fruit set is reduced. The fruit may also be small and misshapen. The quality of the fruit declines. Firmness is reduced and many cultivars may have enlarged tips. Coloration may be affected as well.
There are several models that fruit researchers use to calculate chilling units and a little debate at which one to use. You can check how many chill units by going to our UGA weather website, http://weather.uga.edu.
You do need to know how many chill hours are required for your specific cultivar. Click on the Pine Mountain weather site and then on the chilling hours calculator. The date should be set from Oct. 1, 2015, to today’s date.
As of this writing we had 831 hours so far this winter. As you can see from the chart we are behind previous years. We still have time though. There is a lot of other information that you can explore on that site as well.
What’s going on in Extension?
The Become a Master Naturalist program begins March 31. Call the office for more information.
Small Ruminant Training: March 11, FAMACHA training and nutrition and March 24, reproduction, lambing, marketing, hoof trimming. Call Susan James, Meriwether County Extension, 706-672-4235 for registration information.
Equipment Maintenance Workshop, March 18, 9 a.m. to 3 p.m. Ag Center
Farm to Market workshop. Become certified, March 23. Call the office for more details.
Tree seedlings can be ordered from the Georgia Forestry Commission, 706-845-4122.