Tree Health 101: Common Issues with Mature Trees

A tree can grow for years, and then it seems that suddenly it stops growing, has yellow leaves, deformed leaf or stem growth, or is showing signs of die back and stress.  As it turns out, even old trees need care and attention!

For most newly transplanted trees, a homeowner or gardener will take vigilant care of the new tree.  As time passes and the tree becomes established and has shown considerable growth the homeowner or gardener will back off of their vigilant care and let the tree do its thing!  (I am even guilty of this, and I work at a tree nursery!)   It is true that you don’t need to go out and water your tree every 10-14 days on the nose once the tree is established but there are some practices that should be upheld to make sure your tree stays happy and healthy in your yard.  After all, think about all the time, energy, and money you put into getting it there!

Common symptoms of an unhealthy tree include yellow leaves-or chlorosis, distorted growth, dead or dying sections of branches, or noticeable spots or legions on leaves, stems, and branches.  Each of these symptoms can be caused by different stressors and sometimes multiple stressors at once!  Listed below are the common reasons behind an unhealthy tree and how to alleviate them.

  1. Water requirements are usually the first question to ask yourself when you notice an issue with any plant. Believe it or not you can both overwater and underwater a tree.  When experiencing a drought, established trees may still need a drink.  Their leaves may turn yellow to brown; they may experience scorch and begin to drop.  Leaves dropping may be the trees last attempt at survival by going dormant early.  This also may occur if the tree is sitting in ground that is too wet.  With heavy spring rains and flooding, trees may become suffocated by their roots being saturated with water for too long.  Leaves will look limp, turn yellow and brown, and eventually start dropping from the tree.  This can only be alleviated by allowing the ground to dry out!  Think about the weather patterns from the last month.  Was it dry? Did it rain more than normal?   Did you drain water out of your basement directly onto the root system of a tree?  If nothing seems amiss with the watering situation, move on to the next bullet points!


  1. The tree could not be getting enough nutrients. Just like any other living thing on earth, trees need nutrients, water, and minerals in order to photosynthesize, transpire, and grow.  Since trees cannot get up and look for food and water like other living creatures can, we occasionally need to help them along.  It is important to fertilize and water even mature, established trees when they start to look stressed. We usually recommend using fertilizer spikes, liquid fertilizer mixed with water, or a granular fertilizer mix that you can sprinkle around your trees.   Another practice that helps provide nutrients to the tree is to mulch around the base of it with hardwood mulch.  The mulch not only keeps weeds down and makes it easier to mow around, but as the mulch breaks down into compost it releases nutrients into the soil that can help feed the tree.


  1. Compacted soil and restricted root space can also affect the heath of a tree. If you have a tree in a high traffic area near walking paths or in the back yard where everyone hangs out, the ground at the base of the tree will become hard and compacted over time.  This can be exaggerated in new building sites where heavy machinery and clay based soil is located.  You can aerate your lawn or you can turn over your top soil to help alleviate this issue.  If you choose to turn over your topsoil go ahead and add in some compost! More nutrients couldn’t hurt!  As far as restricted root space is concerned, some trees are planted too close to roads, houses, paved areas, or other buildings.  This limits the amount of space that the roots have to spread and search for nutrients, and can cause the roots to girdle.  Essentially that means the tree roots cut into the side of the tree at the soil surface or just below and restrict water and nutrient flow to the rest of the tree.


  1. Pests like Japanese beetles, spider mites, bagworms, and many others that I’m sure you have heard of can drastically affect the health of the tree, and often times it seems like it happens over night. Once you see a major change in your tree, take a close look at the bark, the top and underside of the leaves, and along the branches.  If you find the creepy crawlies, take a picture and take it to your local nursery.  Often times they can identify the insect and give you a plan of action for treatment.


  1. Finally natural or mechanical damage can have lasting effects to the health of your tree. Clipping the bark with weed eaters or lawn mowers can restrict nutrient flow to the rest of the tree, making the tree appear sick.  Wind and ice storms may also break branches near their attachment points and you may not notice it until the branch starts to die.  Simply prune back the dying branches and your tree should be okay!  Last but not least, animal damage from rabbits eating bark and low branches, to deer rubbing the truck with their antlers can leave lasting damage to your tree.  With both mechanical and natural damage the tree will sometimes heal and sometimes they won’t.  It honestly depends on how bad the damage is and where the damage is located.