Monday, May 23, 2011

Tree Problem 9: Rotten Maple

Site: Street tree on S side of my street. (NE Portland)

+ Big tree providing much appreciated shade late in the day in the summer.
- Has enough decay that you can see daylight through the trunk!

Tree Characteristics
This is some sort of Maple, maybe another Norway (Acer sp.) a young-mature tree with a single trunk DBH 28". Live crown ratio is around 50%.

Tree Health
New foliage looks healthy. Many pockets of decay. Two of the old pruning cuts have decayed together so you could pass something into one whole and out the other!

Site Conditions
Street tree with good southern exposure. Level ground, no direct irrigation except in adjacent lawn.

House, cars, power lines.

Tree Defects
Rotted out core in several places. Constrained root space by sidewalk. Some sidewalk lifting.

Hazard Rating
Part most likely to fail: branch failure. Severe failure potential on large parts with significant targets for a hazard rating of 4+3+4 = 11.

Hazard Abatement
Get inspected (I think this has happened, in fact). Rationale: Some trees can continue to grow even when the core of the trunk has rotted out, need to figure out if this is such a case or not.

Other Recommendations
If it has enough strength to continue to grow the key is to ensure that growth exceeds the rate of decay. Pruning for branch weight would be a good idea.

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