Sunday, May 22, 2011

Tree Problem 6: Norway Maple street tree

Site: N side of street in the parking strip. (NE Portland)

+ Big tree providing much appreciated shade all day in the summer. Significant tree in the neighborhood.
- Norway Maples are getting a bad reputation for being dispersive.

Tree Characteristics
A very large Norway Maple (Acer platanoides) a mature tree with a single trunk DBH 31". Live crown ratio is around 80%.

Tree Health
New foliage looks healthy. Some decay possible at main branch attachments.

Site Conditions
Residential street tree dominating the local canopy. Downslope from a lawn that may receive regular irrigation. No signs of recent site disturbance. Paving under 60% of the dripline, mostly to the North. No evidence of recent changes to paving, fill, or grade work in the dripline. Slope grade flat at base of tree with a 15 degree slope up to the south.

Two houses, cars.

Tree Defects
Constrained root space by sidewalk, street and nearby slope.

Hazard Rating
Part most likely to fail: branch failure. Moderate failure potential on large parts with significant targets for a hazard rating of 2+3+4 = 9.

Hazard Abatement
Investigate possible decay. Prune to remove end weight of large lateral branches. Monitor. Rationale: Need more data to determine if there is decay to be concerned with. It is not clear to me that cabling would be indicated in this case. "There is a limit to the size and weight cable and brace systems can support".

Other Recommendations
Long term it would be good to consider what will succeed this tree and when.

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