Giving Your Trees a Chance at Success
Even though we have had a very mild summer by Oklahoma standards, the fact remains that we are still in a drought and our trees continue to pay a very high price. Sometimes the issue that finally kills a tree may not be the drought, but a secondary problem such as disease (in the case of hypoxylon canker) or a severe insect infestation like borers. While these are indeed significant issues, they are generally not a problem when trees are healthy.
We may not be able to do much about the weather mother nature throws at us, but we can minimize other factors that can also cause our trees and other landscape plants to become susceptible to disease and insects.
Here are some common issues we see on a regular basis that cause significant problems:
- Root damage. Trees have two basic types of roots, structural and feeder. Structural roots are the big ones that anchor the tree. Feeder roots are much smaller and less conspicuous but no less important. These feeder roots are vital for a tree to be able to take up water and nutrients. The majority of these roots are in the top 12” of soil. This makes them easily damaged by tillage or compaction.
- Trunk damage. Deep bark wounds are hard to overcome. When we look at declining trees, this is the most common issue we see. It is common to hear “well, I hit it with the mower, but that was years ago and the tree was fine”. It doesn’t matter, the damage was done. Even aggressive or careless weedeating can eventually destroy the bark enough to shut down a tree’s vascular system. Once this happens, the tree simply cannot thrive.
- Trunk damage also happens when string, ropes, tags or other materials are not removed in a timely manner. Anything surrounding a tree trunk or branch should be loose enough to allow for growth. Once again, if enough damage is done, it cannot be overcome.
- Another very common form of trunk damage on thin barked trees such as maples is sun scald or winter injury. On small trees, install a trunk protector in late fall to protect from large temperature fluctuations on cold and sunny winter days. It is critically important to remove these wraps each spring to avoid girdling or providing a safe harbor for insects.
- Changing the soil grade. This is also a root issue, albeit an indirect one. Avoid adding or removing soil around a tree once it becomes well established. Perhaps the most common offense here is building up a flower bed around the trunk. The root “flare” is the most sensitive part of tree, and covering it with soil (or even an extremely high level of mulch) is detrimental.
- Improper herbicide application. Make sure you understand what you are applying in your home landscape and how it it may affect your trees. For example, a very common broadleaf weed control that is perfectly safe of turfgrass (when applying correctly), often carries the warning: Do not apply over roots of trees! If you have any questions or doubts about the products you are using, give us a call in the Extension office.
- Inconsistent watering on new plantings. Every time a newly planted tree or shrub is allowed to dry to the point of wilt, it must work that much harder to become established. A heavy soaking to make up for forgetting to water after a two week summer vacation is probably not going to be of much help!
For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at firstname.lastname@example.org, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.
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