Care of Freeze-Damaged Citrus Trees – Part I

Freeze damage can be quite a problem at this time of year if you have dooryard citrus trees.  Although citrus trees are cold-tender plants of subtropical and tropical origin and have not developed the effective cold hardening processes typical of temperate, woody, deciduous species, they have the capability for acquiring considerable cold tolerance.  Citrus does not enter a deep dormancy (resting condition) characteristic of temperature-zone deciduous tree species such as apples or peaches.  Rather citrus enters a period of non-apparent growth (quiescence) as cooler temperatures occur.  My information on caring for freeze damage citrus was provided by Extension Citrus Fruit Specialist Jim Ferguson with The University of Florida, Institute of Food and Agricultural Sciences (IFAS).

First, it’s important to know what causes freeze damage on citrus trees.  It’s not just the cold weather it’s more the fact that citrus trees are evergreen, and never become fully doormat.  Dormancy is a natural pause in the growth cycles of trees which allows them to withstand extremely low temperatures without any damage to the tree. So, if you can gradually precondition your citrus tree.  For cold weather, it will not be as severely damaged by the cold, as would a tree in active growth.

There are many ways you can help your tree through the winter months.  Don’t prune the tree during the cold season.  Pruning stimulates growth, and this new growth is very susceptible to freeze damage.  Also cut back on the amount of fertilizer and water that you give the tree.  Keep the tree healthy, but discourage active tree growth, watch for insects, especially spider mites.  Mites have a tendency to build up during the cold weather, and will often kill the leaves on an entire section of the tree.  The tree will send out new leaves, and as I said, these new leaves are very vulnerable to freeze damage.

Sometimes, however, a freeze can catch you completely by surprise.  This is especially true when cold weather comes without warning, preceded by months of warm to moderate temperatures.  These freezes are the ones that do the most damage.  To recognize freeze damage on your citrus trees, there are several things to look for.

The leaves on a freeze-damaged citrus tree will be hard and brittle.  Sometimes they can recover normal flexibility, but if the freeze damage is severe, the leaves will collapse and dry out.  During periods of low temperatures, it is normal for leaves to take on wilted or drooping appearance.  Don’t confuse this with freeze damage.  Frozen leaves will not be wilted – thy will be hard and brittle. 

Freeze damage can also show up on the trunk and larger branches as splitting or loosening of the bark.  The care you give to freeze-damage will depend on many factors, including the time of year of the freeze, the condition of the tree at the time and probably most important, and the weather conditions that immediately follow the freeze.  A natural reaction after a freeze is to want to do something right away.  Actually, there is very little you can do for the tree at that time, because you won’t be able to tell the full extent of the injury until sometime after.  To illustrate this point, twigs and branches may continue to die for up to two years following a severe freeze.

For more information on “Care of Freeze-Damaged Citrus Trees” contact The Gulf County IFAS Cooperative Extension Service or visit our website @ http://gulf.ufl.edu .