tree and shrub care Archives

This spring we have several trees showing signs of stress that are not particularly attractive. Since last fall, something has happened to them. They leafed out late and/or they have some dead branches throughout the tree. More than likely, it is a result of the historic cold temperatures this winter. But it made me wonder about some other reasons these trees may be stressed this spring.

Why trees?

Trees in Kansas are a luxury and one of your property’s greatest assets. To sit under a mature tree on a warm afternoon, enjoy the blue skies and sip your favorite cool drink is a special experience.

Trees need to withstand the rigors of the climate. Trees block harsh winter winds, give you privacy, delineate boundaries, offer great fall color, attract birds and other wildlife that enhance your enjoyment or your landscape, and increase its resale value. Trees are important for all of these reasons and more, but they are not invincible. At any moment, signs of stress can emerge, so we need to understand and make every effort to alleviate problems that may arise.

*Open-grown burr oaks are wider than they are tall (Photo by Lamar Roth)*

Tree Stress Symptoms

Stressed trees are easy to pick out in the landscape. Symptoms will manifest in a number of ways including flaking bark, secretions, distorted or missing growth, insects, foliage issues, dead branches and lack of vigor.

These symptoms are visual clues to internal, external or environmental stressors. Left untreated, these stressors could ultimately kill your tree. Stressed trees are beacons to insects because they are weaker and vulnerable to attack. Compounding factors over a number of years from the same stressors or multiple stressors lead to tree fatality. Here are some common causes of stress in trees.

Poor Tree Watering Techniques

It is true that trees need water to survive, but they need just the right amount of water. Too much or too little can cause a tree to be under stress. These problems can be compounded when planted in our clay soils. Defoliation, yellowing of the leaves and branch die back are all symptoms to avoid. Most trees, if properly situated, can withstand seasons of drought without much extra inputs.

Monitor trees during stressful times such as drought to make sure they don’t need a deep soaking. Keep in mind that waterlogged soils are more problematic than drier soils because proper air exchange by the roots in hindered by extremely wet conditions. Sometimes we see a tree under stress from drought and do more damage by giving it too much water. Give it a deep soaking, but let it dry out between watering.

Install the tree properly

One of the first lessons I learned as a novice horticulturist is how to plant a tree. “How hard can it be?”, you may say. Just dig a hole, put it into the ground, water it for a while and watch it grow. More trees are killed by improper installation than you might realize. Choosing the right tree for the soil conditions, along with understanding mature size, will go a long way to helping that tree survive and thrive.

In our clay soils, I plant the root flair a few inches higher than the soil line in a hole that is at least twice the size of the root ball. I make a small basin around the tree that makes it easier to water and then lightly mulch the basin. It is important to keep mulch away from the trunk of the tree. I stake the tree for the first year and remember to remove the wires that will eventually girdle the tree if forgotten.

For some additional tips on how to properly plant trees, check out my blog post “Steps to Planting a Tree”.

Beware Lawn mowers and Weed eaters

Anything you can do to keep mowers and weed eaters away from the trunk of trees is vitally important. I have seen too many tree trunks damaged by mowers bumping them and people string trimming around the base of the tree, trying to cut down every sprig of grass. A small two to three foot mulch ring provides just the right buffer between the trunk and lawn. I have seen a string trimmer completely girdle the soft bark of a maple tree and kill it in a couple weeks. If you have invested in a tree, protect it from these tree killers.

Mulch Around Trees Properly

The advantages of mulch around trees are obvious. It is one of the easiest things to do and it improves the aesthetics of the landscape. However, too much mulch, mulch touching the trunk, or mulch volcanos around your trees could cause major tree stress. These stressors are totally avoidable with one to two inches of mulch around the trunk, but not touching the trunk. It is important to keep the mulch several inches away from the trunk. Too much mulch will cake up and seal off the soil, impeding proper air exchange by the roots.

Too much mulch piled up at the base of the tree can lead to fungus, rot, low oxygen levels and tree death. — *This is an example of a mulch volcano. Be sure to pull mulch away from trunk of tree and spread out*.

Improper Tree Pruning

Pruning your trees as they mature is a necessary function. I generally prune our deciduous trees during the winter when they are dormant, making sure not to remove more than 1/3 of the growth at a time. Proper timing will allow the tree to begin to heal without opening up the tree to potential diseases and pests. Evergreen trees can be pruned any time but I avoid the hottest part of the year.

Construction Injuries to Trees

Trees often suffer during and after construction projects. Compacted soils and branch or trunk damage can stunt the growth for several years after the project has been completed. It often takes years for compact soils to improve. I killed several nice maple trees after our Visitor Center was constructed because the soil was too compacted. The soil would not drain and they were essentially planted into an undraining bowl. The roots were completely surrounded by water and they drowned and stunk when I pulled the dead trees out. Remember to protect/ fence off any trees you want to save during a construction project.

Environmental Injuries

There are so many nice trees and shrubs from which to choose. We often push the hardiness zones to grow trees that are borderline hardy in our area. As I mentioned earlier, we have a sawtooth oak and gingko that suffered damage from the extreme cold earlier this year. The are coming out of it, but they will look tough for a few years. These trees are not native and remind me to choose native plants first. It also reminds me to be aware of the hardiness of plants we install. Match plants up to your site, including sun, soil, exposure, hardiness, mature size, and moisture.

Trees are resilient, but we can help them by considering their needs. A little homework before planting can alleviate problems through the years. Trees are alive and ultimately affected by so many factors, some of which are out of our control. Who know what the next pest will be? Who knows when the next drought will occur? All we can do is try to create/match an environment conducive to growth.

What needs to be mulched?

I typically focus on trees and shrubs because they benefit most from a new layer of mulch this time of year. I tend to only mulch perennial beds as they are initially planted. More recently, we are planting new beds denser (plants closer together) so that the lower ground level plants fill in and out compete the weeds, making a thick wood chip layer less necessary. In a prairie, there is no mulch in between the plants — low grasses, wildflowers and sedges cover the ground so weeds don’t germinate and cause problems. We are working to mimic that layered planting style.

What are the benefits?

Obviously, mulch is good at stabilizing soil temperatures which is important as colder weather sets in. It is also good for holding moisture and reducing weeds around the base of the trees and shrubs. Aesthetically, mulch gives your landscape a finished look that distinguishes it during all seasons of the year. An often overlooked benefit of mulch is that it keeps the mower and string trimmer away from the base of the plants. As the mulch slowly breaks down, it releases nutrients into the soil and increases the water holding capacity of the soil.

How much mulch is needed?

For trees and shrubs, I prefer to use between two and four inches of mulch. It is important to keep it away from the base of the trees and shrubs so insects and rot don’t become a problem at the stem or trunk. Please don’t create mulch volcanoes, which are death to trees. An evenly spread ring around the base of the plants, replenished regularly, will help them tremendously. For perennials, we only place one to two inches of mulch down and again we keep it away from the stems. This is fine as the beds are first established but as they mature, less mulch is needed because, with the right care, the plants become the mulch.

Should you use landscape fabric?

I am not a fan of landscape fabric. I have seen it do more harm than good especially for many of our native plants. One problem is that it keeps our clay soils too wet, leading to crown rot and other fungus growth. Using landscape fabric also makes it challenging to change your landscape plan in the future. As an alternative to fabric, we encourage the use of large pieces of cardboard covered by mulch. It still provides weed control during establishment but breaks down over time to be incorporated into the soil. Just slice holes in the cardboard to install your plants.

What type of mulch should be used?

Here at the Arboretum, we use wood chips from local tree trimming services. We like it too be fairly coarse so it breaks down slower and is less susceptible to wind. The type of mulch is not really important but texture is important. Finer mulches tend to cake up and seal off the soil which can be problematic to the plants root systems. Many municipalities have wood chip piles that can be loaded and used at little or no cost to you. Why spend money on fancy wood chips when you can get it for next to nothing? Most mulch looks the same after a few weeks in the sun anyway.

Mulch pile shown here is rough and natural colored, showing our prefered texture and style

It is no secret that mulch is great for the landscape. There are so many benefits when you add it to your landscaping routine. A little work now will pay dividends next year.

Tag Archives: tree and shrub care

Tree Stress