Tree Stress

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.

Sawtooth Oak winter damage

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.

How Does Your Garden Grow?

Many of our readers and webinar participants have asked for an update on my native front yard project, and I am happy to oblige! As with every native garden, it had it’s ‘ugly duckling’ phase wherein it was more mulch than garden. This is normal, and patience is key to getting past this phase. Given the right conditions and enough time to mature, native plants will thrive and thrill you.

An Earth-Friendly Garden

Would you believe that not all gardens are ‘green’? I wanted to avoid the use of too many exotics, which take a lot of extra irrigation and often do not provide food for wildlife and insects. My goal two years ago was to decrease the amount of lawn in my landscape and increase quality habitat in my area. Since then I have been pleased to host buckeye, skipper, and monarch caterpillars. I have seen many species of birds swooping over my garden to eat the flies and moths that hang around. With very low water needs, this landscape helps keep my household water consumption low.

Grey Santolina and purple skullcap anchor the front of my low-growing native landscape.
Limestone edging along the curb stops my mulch from sliding away in heavy rains. I also found a few interesting boulders to serve as substrate for hen and chicks. They make a nice focal point, and add structure.

The Best Laid Plants

While we talk a lot about careful planning and design as keys to success with a native garden, a dash of spontaneity keeps the garden fun and fresh. After initial planting, I continued to add plants and deviate from my written plan. That’s okay! Adding lambs ear from my grandmother’s house, and strawberry mint from my parent’s greenhouse made the garden more personal and functional. I continue to fill in gaps here and there as I see them appear. I have learned an important lesson from all of this: if a certain plant doesn’t work out, it doesn’t mean you failed or that you aren’t a good gardener. It might just mean it wasn’t in the right spot! Fill that space with something else you like and try again.

White flowers of thyme spill onto my sidewalk, contrasted with the silvers of lambs ear
and the chartreuse leaves of bluebeard and sumac.

Plant Selection

I mixed natives and non-natives to create a landscape that speaks to me; a space that is visually pleasing and ecologically friendly. Here are some of my favorites that are all growing well together:

  • lamb’s ear (Stachys bizantina)
  • fame flower (Talinum calycinum)
  • bluebeard (Caryopteris sp.)
  • skullcap (Scuttelaria resinosa ‘Smokey Hills’)
  • ornamental onion (Allium spp. )
  • Mexican feather grass (Nassella tenuisimma)
  • prairie dropseed (Sporobolus heterolepis)
  • grey lavender cotton (Santolina chamaecyparissus)
  • sand cherry (Prunus besseyii ‘Pawnee Buttes’)
  • perky sue (Hymenoxys scaposa)
  • horsetail milkweed (Asclepias verticillata)
  • dwarf false indigo (Baptisia australis var. minor)
  • thyme, oregano, and lavender

Stay tuned for future updates as this planting matures and continues to change. We have had such great enthusiasm around our Native Front Yard classes, making me hopeful that many of you are on the journey to more sustainable front yards as well!