Winter is Coming

Written by

Mary Sutton

November 28, 2024

Happy Thanksgiving! It looks like the holiday is bringing our first real taste of cold weather this year. Temperatures in parts of South Georgia are predicted to drop into the low 30s this weekend. While the time spent at freezing temperatures will likely be very brief, it is time to start looking ahead and preparing for this winter. Below I will be sharing a few things to keep in mind and some additional resources for freeze protecting your citrus.

General Citrus Physiology During Cold Weather

The duration of any freezing temperatures is critical. Prolonged exposure to below freezing temperatures is often more damaging than brief drops below freezing.
Citrus trees can acclimate to cold weather. Extended periods of temperatures below 50°F will help acclimate trees for any freezing temperatures they may experience.
Trees with fruit still on them will be more susceptible to freeze damage than those without fruit. Likewise, the heavier the crop load, the more damage that is likely to be sustained.
The age of the tree will factor into its susceptibility. Young trees are more susceptible to freezing temperatures than more mature trees.
Within a tree, the different types of tissue will vary in their susceptibility to freeze damage. Generally, buds/flowers/new vegetative flush are the most susceptible to freeze damage, followed by mature fruit, hardened off leaves, and woody tissues being the least susceptible. The thicker the woody tissue, the less susceptible as well (e.g., trunks are less susceptible to freeze damage than twigs).
Freeze damage occurs when the water within plant cells freezes. This damages the cell membranes and disrupts their function. This damage is usually irreversible.

General Cultural Practices to Reduce Risk of Freeze Damage

There are a few things you can do during the rest of the year, that will set your trees up to better withstand any freezing temperatures.

Keep trees well-irrigated. Likewise, proper nutrition throughout the rest of the year will ensure trees enter the winter with no deficiencies. Stressed trees are more susceptible to secondary damages. DO NOT fertilize trees past August. Fertilizing too late in the season can trigger vegetative flush that will be susceptible during a freeze if it hasn’t had time to harden off.
Remove weeds underneath the trees and mow row middles. In the row middles, weeds and tall grass can have an insulating effect which sounds good but isn’t. Tall grass and weeds will prevent the sun from warming the soil which will keep soil temperatures lower. Weeds underneath trees can have a similar effect, but they can also block microjet emitters reducing their efficacy as a freeze protection method.

Active Freeze Protection Methods

From what I have seen, most people in South Georgia use irrigation, trunk covers, or a combination of the two to protect their citrus during bad freezes. Below are a few tips to keep in mind when employing these methods.

For both, timing is crucial. Freeze protection methods need to be started BEFORE temperatures reach freezing. Trunk covers slow the drop in temperature, so they need to be added before temperatures start dropping. Likewise, water can freeze in irrigation lines and ice can plug emitters, so irrigation needs to start before reaching freezing temperatures.
For both, protection methods need to be implemented for the entire duration of the freeze event to be beneficial. This is especially true when using irrigation: stopping part way through a freeze event leaves trees more vulnerable to damage as damp tissue is more likely to freeze.
For both, protecting the graft union is critical. Trunk covers will generally cover the graft union and a good portion of the trunk. The height of microjet emitters can be adjusted so that they cover both the trunk and lower branches. The less damage the trunk sustains, the more likely the tree can recover.
For irrigation, placement is important. If using with trunk covers, put the emitter inside the trunk cover. If using irrigation alone, make sure the emitter is close to the tree trunk and is directing water towards the trunk and graft union.

We will continue to post more detailed information throughout the winter and keep a close eye on the forecast. Happy holidays!!