Extension Educator, Horticulture
Some rules of life come back to haunt us–finish all the food on your plate, a nice tan is healthy, and plant trees as deep as they were in the pot. Bill Vander Weit, Forester for the City of Champaign, shared his concerns about trees planted too deep. "Many trees we purchase have the root collar buried in the rootball. If this excess soil is not removed the root collar 'suffocates' from excess soil resulting in a disruption of water and nutrient uptake, starting a downward spiral for the tree."
Vander Weit stated that improper tree planting has become so widespread that one observer termed it a "national epidemic." Researchers at the Bartlett Tree Research Laboratories excavated 363 newly planted trees and found that 93 percent had either excessive soil or mulch covering the root collar (the area where the roots meet the trunk commonly identified by a flaring of the trunk).
These trees will probably not survive for more than 2 years though some will survive in a weakened state for 15 to 20 years until some other stress such as drought kills them
Why are trees being planted too deep? One explanation is that people do not pay close attention to root location during planting. The problem can be traced back to common nursery practices. When cultivating between rows, nurseries often build up soil around the trunk. When the trees are transplanted the root collar will be buried sometimes as much as six to nine inches.
To ensure your tree is not planted too deep, do not follow the common recommendation of planting the tree at the same soil level that was found in the purchased balled and burlaped tree.
During planting remove the twine around the trunk, peel the burlap back and remove if possible. Snip off wire baskets if necessary. Then gently scrape away excess soil to reveal the root collar. When planted at the proper depth the root collar (trunk flare) should be visible. If the trunk enters the ground as straight as a telephone pole, the tree has been planted too deep.
Other tree planting tips:
Dig the hole as deep as the root ball and no deeper so the soil under the root ball is undisturbed.
Dig a hole two to three times as wide as the root ball. This will allow roots to grow more easily into this area.
Do not add soil amendments. Old recommendations for adding soil amendments such as peat moss have been discarded. Simply use the soil removed from the hole as backfill.
Prune only broken or dead branches at planting time. Removing live branches removes a source of stored energy important in overcoming planting stress.
Stake trees only when needed as in windy or high traffic areas. Wire even if protected with garden hose can damage the trunk. Use broad-banded materials, check frequently and remove after one year. Wait a year to fertilize unless using a slow release fertilizer. Add three to four inches of mulch such as wood chips. Mulch should not contact the trunk.
Do not wrap trees during the growing season. Wrap can hold moisture next to the trunk and serve as a home for insects.
Don't forget the most important first step–select the proper tree. Avoid the "it's so pretty" impulse purchase. Do your homework. Select a tree with the correct mature height and one that will easily adapt to the soil and planting site.
To help you with tree selection and care, stop by the Extension office for the brochure the "Tree Growing Guide for Central Illinois." There is no charge thanks to the city forestry departments of Bloomington, Champaign, Decatur and Urbana who developed the brochure.