After Cutting a Limb Off a Sugar Maple Tree, Should I Tar It?

Branch Collar

• Pruning cuts can leave the tree trunk vulnerable to infection from decay and microorganisms. The outdated "flush cut and paint" pruning practice aggravates the risk. Each limb has a collar at its base -- a swollen area that sometimes has a bark ridge. The collar contains a chemical zone that inhibits decay. When decay moves down the branch, it stops at the collar. A callus forms and the branch falls off. Cut just outside the branch collar so that the tree's natural defense mechanism is not harmed.

Wound Dressing

• In the past, wound dressing was recommended to prevent decay-causing infection. But at best, wounds don't heal any faster with dressing than without it. Research shows that wound dressing doesn't do anything to prevent decay, and sealed wounds create an environment that suits wood-inhabiting microorganisms. Some types of wound dressings kill cambial cells. The wounds can stay open for more years than without wound dressing. Materials are being tested that may fight infection, but none are on the market.

Sugar Maples

• Sugar maple is a tree that exudes sap when it's pruned in the late winter or early spring. Tree sap, gums and resins help trees combat invasion by pathogens. Sap flow doesn't usually hurt the tree, but it can be unattractive, and excessive "bleeding" can weaken it. Prune sugar maples in the late spring, summer or fall to reduce sap flow. Avoid unnecessary pruning by choosing the right location for the sugar maple, so that it has the space and conditions for its natural growth habit.

Oak and Elms

• Wound dressing is recommended for oaks and elms, when they are wounded at a critical time -- spring for oaks and throughout the growing season for elms. Whether the damage is from storms, accidental mechanical wounds or necessary pruning, some type of wound dressing should be applied to the wound within 15 minutes. This is specifically to prevent the introduction of pathogens from oak wilt or Dutch elm disease. Latex paint can be used as a wound dressing.