Re: Cabling the Cracked Sweetgum
Just climbed it yesterday; here is the report:
ASSIGNMENT September 13 2008 of the Association asked me to assess the condition of a tree at , and describe reasonable management options. Per the request of the city arborist, I was assigned to determine whether a support system could comply with the American National Standards Institute (ANSI)’s standards on support systems, so I refer to ANSI A300 (Part 3) 2006. I am not certain whether my client is the City , the Association, both, or neither. I agreed to inspect the tree as soon as possible given the emergency conditions.
OBSERVATIONS AND DISCUSSION
The tree forks out a foot above the ground. The smaller fork has a moderate lean over the road and powerlines. Lower branches have been shortened to avoid the powerlines, but higher branches extend over them and over the property across the street. The larger trunk has a slight lean toward the Taylor residence. The fruit is in its green stage, with more water and more weight.
A crack between the trunks has opened this summer and is now 1-2” wide. There is no visible decay inside the crack at present, but the wood is highly likely to decay in the future. There is a small amount of decay in a ground-level wound facing the street. The trunk shows no defects, and the wounds from pruning branches appear to be sealing well. There is one fork above the with included bark. Many branches on both trunks have heavy ends. The top of the tree has less leaves.
Both trunks form major scaffold limbs about thirty feet up. I climbed the tree to complete my inspection, and in light of the considerable hazard I tied the trunks together with rope to prevent further failure and damage. I read the relevant portions of both the ANSI standards and the Best Management Practices (BMP’s) published by the International Society of Arboriculture. I saw the last 5 panels of the sidewalk lifted, and the grass near the tree is brown, indicating aggressive root expansion and water uptake. The asphalt pavement on Road has small cracks, allowing infiltration of water and nutrients and gas exchange.
MANAGEMENT OPTIONS
1. A 3/8” Extra High Strength (EHS) cable properly installed below the scaffold forks would comply with ANSI standards. Rated at 13,600 pounds, it can support the defect and work to prevent further opening of the wound.
2. The branches can be shortened, reducing strain on the defect and perhaps allowing the trunks to be pulled closer together when the cable is installed. If sufficient pruning is done every 5 years, and decay does not spread rapidly, the cable may be strong enough on its own.
3. The trunks can also be bolted (braced) together, but ANSI standards do not require this treatment. The ISA BMP’s state that brace rods are used to stabilize forks that have cracked. Propping and guying are support methods that do not seem to fit this tree.
4. Removing the five sidewalk panels and adding 4-6” of loose soil and sand before possibly relaying them would provide more rooting area for the tree. So would mulching an area extending in an arc around the tree, where the grass is brown and woody roots protrude above the surface. Chopping the leaves that drop this autumn and spreading the chips from the pruning work about 4” deep would more closely approximate the nutrient recycling and root protection in the tree’s natural growing conditions. The rooting area beneath the gravel driveway could be aerated and fertilized, according to its needs. Testing the soil, adjusting the acidity, and adding prescribed nutrients might also improve the tree’s ability to strengthen itself, over time.
The work should be done by a Certified Arborist experienced with the treatments specified, especially pruning over power lines and designing and installing support systems.
This concludes my report. I can clarify any portions of it upon request.
Sincerely Yours,
BCMA
