Expert: Jim Hyland - 1/30/2007

Question
How close can I excavate to a cedar tree without damaging the root system? Is there a standard width based on the branch diameter of the tree?

Answer
An approximate rule of thumb is to use a root ball 20 times the diameter of the trunk (as measured just above the basal flare) for trunks up to ½” in diameter, 18 times the diameter of the trunk for ½-1” diameter trunks, 16 times the trunk diameter for trunks 1-1½” in diameter, 14 times the trunk diameter for trunks 1½-2½” in diameter, and 12 times the trunk diameter for trunks 2½” to 4” in diameter. For most trees and shrubs, the root ball depth should be about 8” for a 12” diameter root ball, ranging up to about 18” for a 48” diameter root ball.
Cutting the root ball free from the surrounding soil so that it can be moved. This can be done in various ways. For small root balls (up to about 12-14” in diameter), an ordinary spade may be used to carefully slice the root ball free from the surrounding soil. The best spade for this purpose should be sturdily constructed, with a long, narrow blade cut square across at the tip. Such spades are sold commercially as “nursery spades”. Also available are the less sturdy “drain spades” - these have long, narrow blades which are usually rounded at the tip. Whatever type of spade is used, it is helpful to keep the cutting edge quite sharp. Keeping the blade clean and smooth helps also. Coating the blade with silicone lubricant or a similar product can help.
Stabilizing the root ball to help ensure that it stays intact during the transplanting process
Lifting the root ball out of the ground so that it may be transported to its new location.
Depending on the digging method used, steps 3 and 4 may be reversed.

This root ball can be quite heavy depending on the size of the tree. The transplanting success will go down as the tree size goes up. Large trees do not transplant well unless a machine called a  tree spade is used and this will take a professional to handle this large job. Here is a web link to the use of a tree spade. http://www.sustland.umn.edu/implement/treespade.htm

The next important thing is the new hole for the tree. It should be twice the size of the root ball and fill the excess space with good top soil and mulch.