This material was abstracted from 100 Tree Myths* by Dr. Alex Shigo, in which he lists myths which can be seriously injurious to trees. According to Shigo, myths are “misconceptions, misunderstandings and half truths” which persist in our folklore about tree care. We have surveyed Shigo’s myths, and are discussing those that are most appropriate for the homeowner.
Trees are so big and tough that nothing can injure them. False. Trees all over the world are being
mutilated and are dying as a result of injuries from people. Most common injuries are: trees that are incorrectly planted; planted in the wrong place; or damaged during construction.
Before planting a tree, prune living branches to balance crown with roots. False. Removing living branches takes food from the tree. Each leaf is a food factory and recently planted trees need a lot of food. Do remove dead and injured branches at planting time. Leave all live tree branches on for a few years.
Plant deep and the roots will grow deeper. False. The roots will grow upward if planted too deep.
Roots growing upward cause lawn problems and break sidewalks. Cutting these roots will cause even more problems.
Lots of mulch is good. False. Apply three to four inches of mulch at most, and keep it six inches away from the trunk to reduce rodent damage. Excessive mulch interferes with aeration and moisture for the roots.
After planting a tree, brace it tightly. False. A tree should be able to sway. Do not brace it too tightly. Use broad belt-like strapping that will not injure the bark, and do not use a wire in a hose.
Trees will heal wounds. False. Trees cannot restore injured tissues in the same spatial position. When trees are injured or infected they chemically strengthen the boundary between injured and healthy tissue, forming a new anatomical and chemical zone, which separates the infected wood from the healthy wood. This is called compartmentalization.
Clean cavities deep into sound wood. False. Cavities can be cleaned as long as the protection boundary that has formed around the wound is not broken.
Prune living and dead branches flush with the trunk. False. Flush cuts destroy the tissues that form the branch protection zone. Cut branches just to the callus, so you get a nice unbroken, circular callus. The size of the swollen collar at the branch base determines the angle and position of the correct cut.
Wound dressings and paint stop rot are beneficial to trees. False. These treatments mislead owners to believe that they can flush cut, top, tip, dig deeply into wounds, insert drain tubes, and inject deeply into trunks without injuring the tree, because there is a remedy out there to undo what was done. Wound dressings and paint provide a home for insects and fungi.
Injections and implants do not injure trees. False. These invasive techniques repeated many times can cause serious internal injuries to trees.
Trunk wrap prevents cold and heat injury. False. There is no data to support this practice and it could keep the sun from hitting the green photosynthetic layer in the trunk. and deprive it of food. Wraps over wounds and flush cuts make perfect conditions for infestations.
Decay is only a problem in old trees. False. Young trees in cities receive many wounds that lead to de-cay. Wounds from lawn mowers, cars, string
trimmers, crushed roots, wire bracing, and flush cuts must be avoided.