Inula Royleana
Midwest Gardening
Stressed Trees and Evergreens

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The weather in recent years has been unusual and extreme, causing stress to deciduous trees and large evergreen trees

Stressed Oak Tree

A couple of my neighbors have asked me this summer if I know what is wrong with my trees and if I am going to take down those bad branches.  I decided many weeks ago to just leave the poor things alone and give them time to recover from stress.  I will wait to see how they look next year.

 

Many of our plants and trees have been stressed by a number of weather factors over a period of two to three years.  Many regions have seen extended periods of extreme drought as well as extended periods of heavy rainfall.  Northern regions have seen winters with very little snow accumulation and winters with very heavy snow accumulation.  Not to mention long summers, then long winters and repeated cycles of freeze and thaw in both autumn and spring. 

So what is all this doing to our trees and evergreen trees?  The effects of these stresses vary and have been compounded by multiple stress factors.  It is interesting that as I have been making my notes to outline this article, I find an article on just this subject by Dave Orrick of the Pioneer Press.  His interview with the Department of Natural Resources confirms my suspicions  about the weather related stress to trees and evergreens.  Jana Albers of the DNR also reinforces my decision to let nature take its course as the 2013 growing season has improved conditions dramatically.

Soil that remains saturated for long periods cause trees to lose the lower roots because water near the soil surface is overly abundant, making a large root system unnecessary.  If followed by drought the roots do not extend deep enough to reach water.  Extended and repeated drought will of course cause the tree to starve and die.  In the meantime, the stressed plant is vulnerable to disease and insect problems.  Problems can be further complicated if your trees or evergreens are assaulted by salt and de-icer chemicals commonly used on roadways in cold regions. 

In our home landscapes our plants may not suffer as severely as they do in natural areas.  We typically supply supplemental water during drought.  And properly graded landscapes allow the soil to drain and dry out relatively quickly.  But minor stress is caused nevertheless.  Although a winter of little snow sandwiched between dry summers has taken a toll on our trees.  So far this year though we have seen plenty of rain in most regions (way too much in some), so I expect that our trees now are well on their way to recovering.  Given adequate moisture through this fall and hopefully an uneventful growing season next year and they will likely be just fine.

Drought stressed evergreen tree

We have seen compound stresses to the trees recently all across the country, so diagnosing a problem can be difficult since so many factors are at work.  All the more reason to let nature take its course if you can not identify the problem and therefore the solution.  Guessing could make the problem worse.  Be careful about diagnosing, but here are a few things to look for:

  • Drought will often cause leaves or needles to become limp, droop, turn yellow and then drop if the drought is severe.  Often these symptoms do not appear immediately and could even surface the following year.  Eventually limbs will die back and the entire plant could eventually starve and die.  If drought is not extended or severe, growth can be slow or stunted for more than one growing season.
  • Too much water is harder to pin down, the symptoms can be highly variable.  More obvious signs can be chlorosis (the leaves may turn yellow to white), slow or stunded growth, wilting and dropping leaves and/or small limbs dying back.
  • Winter injury can be quite prevalent on evergreens in particular.  The needles may turn brown and drop and dieback can occur.  Watch for split bark on deciduous trees.
  • There are a number of diseases and insects that could be causing a problem with your tree or evergreen.  If you are not sure that your tree needs water, or that it needs to dry out after severely extended periods of rain, it is often best to consult an arborist.  In any case, do not indiscriminately apply fungicides or insecticides.

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