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Renovation & Design

Cable-bracing system a safer way to secure tree

I recently met with a client who had a 70-foot-tall Manitoba maple tree on the property.

The tree was about 75 years old and for its species, getting close to the end of its life time. Older trees such as maples, willows and poplars whose wood lacks the strength of an oak or elm can fail during strong wind events. The client's tree experienced a great deal of branch breakage in the past. Wood decay was very prevalent in those branches.

This tree also had four prominent secondary trunks originating from a common stout base trunk. One of these sub trunks had been heavily damaged by woodpeckers feeding on overwintering grubs (wood boring larvae) close to that trunk's origin at the main base trunk. For safety reasons I advised the owner that this damaged secondary trunk must be removed. For this owner, removal of the entire tree was not an option. Is there a way of making the tree relatively safe without significantly cutting or topping the tall secondary trunks?

Exposing the damaged secondary trunk through removal exposes the area of attachment where the remaining secondary trunks originate from the base trunk. Potentially wood decay and further woodpecker damage could cause the failure of another secondary trunk. I advised the owner to have a professional arborist install a cable-bracing system connecting all the secondary trunks to one another.

The Cobra Tree Bracing system is the method most commonly used in the Winnipeg area. Special cables are used to connect the secondary trunks together. Images of this system are beautifully shown and described on the Cobra website: http://www.cobranet.de/en/pdf/cobra_us_brochure.pdf.

For copyright reasons, I cannot use their images in this article.

No system is completely fail-proof. The cables will limit catastrophic trunk failures, but it should always be remembered that an old maple tree can be unpredictable.

I recommend that if this is a solution for your trees, that you contact two or three licensed Manitoba arborists for quotes, especially those certified by the International Society of Arboriculture. If you contact me, I will send you a list of these arborists.

Michael Allen M.Sc.F., RPF is a consulting urban forester, tree diagnostician and certified arborist. He owns Viburnum Tree Experts, a Manitoba company that provides objective assessments of the condition and the care required for trees and shrubs on home and business landscapes. He can be reached at 204-831-6503 or viburnumtrees@shaw.ca His web site is www.treeexperts.mb.ca.

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