Deadly – Planting Too Deep, Don’t Do It!

There is an old expression in the green industry that, while over-simplified, still has value: “Plant too high, plant won’t die. Plant too low, plant won’t grow!”

Both planting too shallow and planting too deep can be problematic. This post will address the issue of planting too deep, which contributes to the decline and failure of landscape trees and shrubs. The good news: this can be avoided completely by planting at the correct depth!

You might be asking yourself: “How can I tell if my tree or shrub is planted too deep”?

  • Some new growth may develop each spring, only to die-off during the stress of summer.
  • Advanced symptoms of depth-related stress are cankers and deep cracking of the bark. A canker is an area of dead tissue on a woody stem. Some shallow cracking of bark is normal for many trees as the trunk grows but there is a problem if the bark is also peeling near the cracking.
  • A tree may survive until fall but may not survive the winter because of insufficient storage of food reserves caused by the damaged bark.
  • Deeply planted trees tend not to be very vigorous and look like they are struggling to grow. 
  • If the root flare is not visible then be suspicious of deep planting or another problem such as girdling roots. Girdling roots are hidden from sight but one above-ground diagnostic is to check to see if the tree has a trunk flare or not.

Here is a textbook example of planting too deep. An arborvitae was killed by being planted FAR too deep.  You can clearly see the “soil above our soil” – soil that is piled far above the root ball and potting media. The blue line indicates the appropriate soil level.  This evergreen was planted at least 4-6” too deep (circled in red).

If you have noticed trees on your property that were planted too deep, is there anything you can do to help them survive? Possibly!

Solutions for planting too deep include replanting and root collar excavation. If a tree or shrub was planted recently enough, it can usually be lifted and replanted. In some cases, it is possible to remove excess soil and mulch from around the root collar.

A pamphlet from the Brown County UW-Extension defines the root collar as “the interface region of the tree trunk and root system where the trunk flares up near the soil line.” This flare should be visible and exposed to oxygen – not buried under soil or covered by mulch. When a tree is planted too deep, roots which grow horizontally stay deeper than they need to be to take in air and allow the tree to respirate.

There are numerous potential consequences of planting too deep. It can have negative effects on tree growth, including root defects such as girdling, circling, or kinked roots. Growth of the tree may occur more slowly and/or leaves may be lost early in Autumn. At its worst, planting too deep may result in premature death.

While girdling roots are located below the surface and we are not blessed with x-ray vision, many trees with girdling roots will have a flat side in the trunk.  This is a helpful visual diagnostic that can point to a problem underground.