Failure to Thrive

The vast majority of diagnostic questions I receive each year are related to trees with health issues. Many of these issues could be avoided by proper (and consistent) care of the tree from the day it is planted. Sometimes things do go wrong, and knowing what to do can be instrumental in reviving the health of a tree.

Trees have the amazing ability to “compartmentalize” diseased and damaged tissue, and to produce healthy tissue around it. If a tree has been stressed by environmental issues such as compaction in the root zone, drought stress from lack of irrigation, mechanical damage (like that caused by deer or sapsucker woodpeckers), or a host of other issues, the tree’s ability to recover from such damage becomes compromised.

What can we do to help the tree recover from these stressed conditions?


The first thing we do is look at the base of the tree, called the root flare. Look to see if the “original” soil line is exposed, or if the trunk has been covered by additional soil or mulch. Pull back the soil/mulch until you see roots growing from the trunk. If you find that the root flare has been covered, pull all soil/mulch back at least 6” from the trunk. If the tree seems to have extensive amounts of soil added around the trunk, it will be necessary to hire an arborist to use an “air spade” to remove the soil around the root flare.



Compacted soil will benefit from “plug aeration”, and should be aerated to a depth of 6”-12”. Aerate soil 2’ out from the trunk to the drip line or beyond.

After aerating the soil, a 1” layer of compost followed by a 2”-3” layer of hardwood mulch should be applied, again to the drip line or beyond. Avoid applying either of these too close to the trunk of the tree.

Fertilization should take place in mid-April and October and should always be an organic form of Nitrogen. MicroLife products contain beneficial mycorrhizae fungi and beneficial microorganisms which aid the root system in uptake of water and nutrients. The organic Nitrogen is in a water-insoluble form, and requires microorganisms to break it down to a usable form. This provides a slow release of Nitrogen that cannot be leached away by rain or irrigation.

Avoid using chemical fertilizers, insecticides or fungicides unless a diagnosis has been made and recommendations come from a reliable source. Herbicides should never be used under the canopy of a tree, and drift from use of herbicides should be closely monitored.

Dead and/or damaged limbs should be pruned by making a cut at the “branch collar”, using a sterile, sharp pruning tool. (see pruning diagram)

Established trees benefit from a consistent watering regime. Watering should be directed to the entire area under the canopy of the tree, and even beyond, in some cases. The majority of the “feeder” roots are in the top 12”-18” of the soil, and the tree would benefit from infrequent deep watering vs. frequent shallow watering. Often our trees are located in our lawns, which are generally watered to a depth of 6”. An occasional deep watering cycle would be appropriate, especially in a drought year.

Facts About Trees

Here are some interesting “tree facts”:

  • A tree’s roots can extend 1-2 times the HEIGHT of the tree OUT from the tree!
  • The majority of the tree’s root system is located in the top 12”-18” of the top of the soil because the oxygen that the roots require to function is located there.
  • A tree’s roots absorb water and nutrients from the soil, store sugar (carbohydrates) and anchor the tree upright. Each root is covered with thousands of root hairs that make it easier to soak up water and dissolved minerals from the soil.
  • A tree’s vascular system is comprised of the xylem which carries water and nutrients, and the phloem which moves sap (sugar and nutrients dissolved in water). It is is located just under the bark of the tree.
  • The “heartwood” in the interior of the tree is “dead” xylem tissue. The main function of the “heartwood” is to support the tree.
  • A tree’s bark originates from phloem cells that have died and been shed outward, and protects the tree from insects, disease, storms and extreme temperatures.