**ARCHIVED POST **
After the recent Winter Storm Uri, gardeners and nature lovers across Texas have been left wondering whether their plants and trees will survive; and if they survive, how to rehabilitate them so that they are healthy and have an aesthetic appearance. Sometimes the same species of trees will show differing levels of damage. This is due the microclimates the trees are in – whether they had more shelter from the wind, or whether other trees or structures blocked ice and snow accumulation. Or perhaps the tree had more snow and less ice and was insulated from the truly freezing temperatures. It is also true that the genetic lineage of the tree can make a difference. If your live oak comes from a genetic lineage that is at the northern range, it may have suffered little cold damage.
Winter storms cause two types of damage – loading damage and freeze damage. Loading damage is the damage caused by the buildup of ice and snow on the leaves and branches. The damage is seen as broken branches, split trees, and bowing trees. The damage is usually immediately obvious, although a lot of bowed trees will return to their normal upright form in very short order. Freeze damage is much less obvious and the full extent usually isn’t known for several months. Freeze damage can be limited to smaller twig death or can kill the whole tree. Leaf buds never open, the twigs and branches become brittle, there’s no green under the bark, and the bark separates from the wood. Freeze damage can also cause frost cracks – areas where frozen bark splits open. The sign that everyone has noticed is the green leaves of live oaks and Mexican white oaks turning brown.
Immediately after the storm, our first thought is to get out and “fix” it. But we need to be patient and give the tree time. If there are limbs that are broken and hanging in the tree, go ahead and prune those for safety. If your tree is an oak, paint the wounds. If the tree has a split, but both halves of the tree are still there, you can have an arborist come in to bolt the split together and create a pruning plan to reduce the weight and improve the structure of the tree. For the first few weeks, only address issues of safety. When you prune, be sure to make your first pruning cut from the bottom of the branch to prevent the branch peeling down the tree. Many trees that would have survived the storm fine were killed when the person pruning it didn’t prevent peeling and the bark peeled all the way down to the ground.
If your tree suffered from frost cracks – the bark froze and split away from the tree – you have options. If you think the tree will be undisturbed, leave the bark. If the tree is in an area where humans and animals will be unable to resist picking at the loose bark, you can perform “bark tracing” – cut away the bark that has separated from the tree, being extremely careful not to damage the bark that is still attached to the tree.
After you’ve taken care of the immediate health and safety issues, you really just need to wait. You can perform the “scratch test” (scratch a section of bark to see if it’s green underneath) to see if the limb is still alive but this does cause some damage and stress to the tree. If by mid-April the leaf buds haven’t swollen and started opening, then it’s time to check to see if the branch has died by using the scratch test. And if the bark has started cracking and flaking off, that’s often a sign the branch is dead (assuming it isn’t a tree that has naturally peeling and flaking bark). If the branch is dead, you can prune for safety and aesthetic reasons, but the tree won’t care if you don’t.
A lot of people are worried about their flowering trees. If the tree blooms on old wood (fruit trees, huisache, etc.) and the tree had already started blooming, we can expect the bloom to be subdued this year. If the tree had not yet started blooming, the buds will likely have survived the freeze, unless the whole branch is dead. Trees that bloom on new wood will not have an impact to their blooms, except that the overall tree may be shorter and less dense due to dieback.
So, now what? You want to “do”, you want to “fix” your trees. But be patient. We want to limit all pruning to just what is needed for safety because if we get another freeze, the dead branches provide insulation and protection to the living tissue. But you can “do” – water your tree, make sure it gets about an inch of water every two weeks, either from rain or irrigation, and add mulch. If you can stand it, extend your mulch ring all the way to the drip line of the tree. Don’t fertilize yet, though. Studies show that fertilizing trees causes them to prioritize new growth over compartmentalizing current damage and creating defensive compounds to protect them from insects and disease, although a very thin layer of compost could be beneficial. But mostly, be curious and watch and wait, find your “inner scientist” and observe.
There are several resources I recommend for tree care after a freeze. This Texas Forest Service guide will help you determine whether you need the help of a certified arborist: https://tfsweb.tamu.edu/afterthestorm/
This brochure gives special guidance for live oak owners to prevent oak wilt: https://texasoakwilt.org/backend/Docs/Materials/Ice%20Damage%20and%20Oak%20Wilt.pdf
Morton Arboretum provides more detailed explanations of types of damage a freeze may cause in trees:https://www.mortonarb.org/trees-plants/tree-and-plant-advice/horticulture-care/winter-injury-trees-and-shrubs
**ARCHIVED POST**
**ARCHIVED POST LINKS & PICTURES MAY NOT WORK**
**ARCHIVED POST AUTHOR: rebeccajohnson
