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To Seal Or Not To Seal? The Deal On Pruning Wounds
Pruning is essential to maintaining a desired shape on trees and shrubs. It also helps control their growth and decrease vulnerability to disease. Because this seasonal chore creates stronger and healthier trees, you’ll also have less damage and clean up after storms.
We’ve come across many homeowners who have been advised to seal pruning wounds in order to prevent pathogens from being absorbed into the cut. Before we dissect the implications of sealers, let’s cover the basics.
What Is A Pruning Sealer?
Pruning sealers are typically petroleum or asphalt-based wound dressings that claim to protect trees and shrubs from insects and disease, while aiding in the repair of abrasions.
These compounds advertise that they create a barrier to protect exposed wood from outside threats. However, sealants actually trap moisture in and decay, which creates a breeding ground for pathogens to feed. Sealing the cuts also stunts new wood from forming, thus slowing healing further and promoting rot as decay organisms and moisture are held within.
How Trees Heal
Trees acquire injuries in many ways aside from pruning. For example, a small area of injury results when a leaf falls, and larger wounds occur when branches break from high wind or animal damage. Any wound is naturally isolated as the tree forms wood that physically and chemically prevents the invasion of pathogens.
A callus develops at the edge of a wound site, and gradually expands toward the wound's center. The damaged area remains, but the tree is not in danger of infection. Sealing a tree's wound is essentially an aesthetic practice that does nothing to help healing. Contrary to claim, these products inhibit the formation of the callus, a situation harmful to the tree.
Best Pruning Practices
Trees and shrubs recover from pruning and prevent diseases autonomously without the need for a Band-Aid. However, there are some tips and tricks to ensure you do not compromise the health of your tree when making cuts.
Prune during fall or winter when temperatures are lower than the rest of the year. During these seasons, infection rates and insect populations are typically at their lowest points. If you prune during warmer months, it is wise to apply a light layer of insecticide or fungicide, not sealant, to wound sites.
Sterilizing your pruning gear before and after use also helps reduce the transmission of certain plant diseases.
When pruning a small branch or twig, cut it back to an intersecting branch or a vigorous bud that points in the direction you wish the new growth to take.
Don't leave a stub over the bud, but don’t cut into the bud either. Cutting on a slant when removing a limb that grows upward prevents moisture from collecting in the cut.
If you must prune a branch more than 1 1/2 inches in diameter, then start cutting the underside of the branch 6 to 12 inches outward from the trunk, but cut only one-third of the way through the branch at that point; make a second cut at the branch's top but 3 inches farther from the trunk than the underside cut. Cut toward the underside cut from the branch's top until the branch falls away.
The stub that remains should be back to outside the branch collar, which is the slightly thicker area where the branch grows from either the trunk or a larger branch.
For more direction on how to avoid common pruning mistakes click here.
To see our top pole saw picks for pruning, click here.