A couple of months ago I wrote an article on the possibility of damage due to the very cold temperatures that we experienced over Christmas. I would like to revisit this topic, because now we are seeing more and more plants starting to try and grow that have freeze damage. Let’s talk about what to look for and how to treat plants that have freeze damage.
All plants have some level of cold tolerance. Some plants have more than others. In perennial plants the amount of cold tolerance that plant has depends on its level of dormancy. Plants that are 100% dormant can experience some very cold temperatures and not sustain any damage when they start to regrow. There are some things that can affect the level of dormancy that a plant has. Fluctuations in temperature affect dormancy. Plants do better in winter if it gets cold and stays cold. When the temperature goes up and down plants can get confused and think that spring is on its way. This is a common issue that we have compared to places further north. Plants that are stressed don’t go into dormancy as easily either. Not enough water, disease, insect pests, not enough sunlight, and age are some of the things that can cause stress on plants. If you have plants that are experiencing stress their dormancy won’t be as deep, leaving them more susceptible to freeze damage. Plants that are not in their correct USDA zone will not handle the cold as well.
Freeze damage occurs when the temperature inside of plants is cold enough for ice crystals to form. This will break plant membranes causing that portion of the plant to dehydrate and die. Because the damage occurs inside the plant it can be difficult to know if your plants have freeze damage, until they start to grow. In perennial plants with large trunk and branches you can start to look for splits in the coming weeks, as evidence of freeze damage. Some plants may look fine, but then as we get into summer have large brown patches in them. These are plants that had some damage to their xylem, and were able to grow until summer when their xylem had to move more water because the plant was transpiring more.
You will need to go through and examine your plants on a case by case basis. Some will have damage and some won’t, it depends on how well they were able to handle the cold. Look for dead tissue. If plants were frozen they will have dead leaf buds that just crumble in your fingers. If you find dead tissue the best thing to do is to prune it out. On some plants this might result in you cutting them back pretty far. The dead tissue is an opportunity for disease to enter the plant. Some plants may have died back completely and will need to be removed. If a plant is mature and is completely dead on the top, it may be able to regrow from the roots.
If you have questions about freeze damage contact your County Extension Office or email me at Jacob.Williams@uga.edu.