Announcements

by John Millikin

Yesterday I received an update from Project Manager Dave Anglin; unfortunately one more maple tree (near 7721 Hayfield Road) must be removed; this will occur sometime between January 23 and the middle of February. We know that in a $7,000,000 project that there will be unforeseen surprises like this one. I encourage everyone to read the justifications that Dave provides and to remember the overall significant benefits that this project brings to Hayfield Farm residents.

Here are the justifications that Dave Anglin sent on Wednesday January 22

“Attached are two pictures showing the circumstances regarding this (maple) tree. Below is a summary explanation with more details in the attached picture mark-ups.

The work is not just encroaching some into the critical root zone. With the work required at this location, the open excavation and required trench box will be well within the tree’s drip line. Add the additional space required to prune the roots and this is up to the tree trunk/root crown. So, root pruning will sever the tree’s root system greater than 40 percent. This poses a severe risk that this size tree will not survive the work in the long run.

Additional risks, beyond/addition to the survivability question:

• Immediate – this tree is near an area where problem soils started slumping/collapsing into and ground water was encountered in the open excavation. So, if the supporting soils slough, this poses a risk to project personnel and near-by others/property of immediate tree collapse.
• Long-term – large structural roots will be cut on virtually half the tree. Short of the tree dying, severing major structural supporting roots risks the tree falling in the future during wind events and/or during very wet weather.

Given the design, I now believe this was always unavoidable. I just wish we had foreseen so the information could have been shared earlier.”

Here is the text in the first picture:

“Painted white line marks approximate location of the excavation cut. Another 6″ of excavation is required to accommodate the trench box to support the excavation sides. The root pruning would then be located at least another 18″+ closer to the tree creating another 6″ cut into the soil. This would put the root pruning inside the two stakes on the left above and cutting through the tree’s root crown.”

Here is the text in the second (close-up) picture:

“Painted white line marks approximate location of the excavation cut required for the necessary work. Another 6″ of excavation – beyond the white line – is required to accommodate the trench box to support the excavation sides. The root pruning would then be located at least another 18″+ closer to the tree. The pruning creates another 6″ cut into the soil. This would put the root pruning inside the two nearest stakes supporting the orange fence – virtually into the tree’s root crown.”

RESEARCH LABORATORY TECHNICAL REPORT from Bartlett Tree Experts

Root Pruning

Kelby Fite, PhD, Plant & Environmental Science and E. Thomas Smiley, PhD, Urban Forestry

Root pruning is the process of cutting roots prior to mechanical excavation near a tree. Root pruning may be necessary to minimize damage to the tree’s root system during construction or in preparation for large tree transplanting. Improper root pruning and root damage from excavation can cause great harm to a tree which may affect tree health and/or structural stability. A tree risk assessment should be performed prior to cutting any roots and alternative techniques, such as boring under the roots, should be considered.

Root Pruning Methods

When pruning roots, there are guidelines regarding size: roots less than one inch (2.5 cm) in diameter can easily be cut with hand tools while cutting roots greater than three inches (7.5cm) in diameter should be avoided whenever possible. There are three general methods of root pruning in the one- to three-inch diameter range:

1. Air/Water/Hand Excavation and Pruning

Excavating roots requires the use of the AirSpade®, hydro excavation or hand tools. This exposure allows the arborist to evaluate the best places to cut, preferably beyond sinker roots or junctions. Roots can be cut most cleanly with a sharp saw or lopper. Exposed fine roots that are to be preserved may be covered with burlap and sprayed with water, or they can be sprayed with a hydrated, fine, water-holding gel to prevent desiccation.

2. Root-cutting Machinery

A root pruner, such as the Dosko or Vermeer Root Pruner, is faster than the previous method (Figure 1). These tools have teeth similar to a stump grinder and provide relatively clean root cuts. However, this method does not allow for the arborist to evaluate the exact location of the pruning cuts and will, likewise, be indiscriminate.

3. Trencher or Excavator

A chain trencher or excavator is one of the worst ways to prune roots because they often lift surface roots out of the soil until they break and leave other roots crushed or torn. After using a trencher, it is better to prune the damaged ends by hand than to leave them untreated. Sometimes, due to site constraints, trenchers are the only option due to their flexibility.

Root Cut Placement

The further from the trunk that root cutting occurs, the better, but generally root cuts made outside a normal dripline of a tree rarely cause permanent tree damage. The preferred minimum distance from the trunk to the closest root cut is 5 to 6 times the Diameter at Breast Height (DBH).

For example, with a 12-inch (30 cm) diameter tree, the root cut distance should be 60 to 72 inches (5 to 6 feet, 1.5 to 1.8 m). At this distance, there should be minimal impact on the health or stability of most tree species with proper aftercare.

For root cuts on only one side of a tree, the root cut distance can be somewhat closer to the trunk than cuts on more than one side. The preferred minimum distance in this case is three times the DBH. For example, with a 12-inch (30 cm) diameter tree, the distance would be 36 inches (3 feet, 0.9m) (Figure 2). This distance is too close if there is pavement over the other side of the root system, if the tree has root decay, is leaning or has other indications of root disturbance. These trees also need proper aftercare to reduce the risk of health problems.

In all cases, consider variables such as tree species, age, tree health, and soil characteristics (including the presence of underground root obstructions) when determining location of root pruning. Cuts made closer to the trunk may dramatically compromise stability and health and should be avoided.

Plant Health Care Before and After Root Pruning

Tree health and soil moisture should be monitored frequently following root pruning. Root pruning should not be done immediately prior to or during a drought period unless the tree will have adequate irrigation. Irrigation should be applied prior to and after root pruning if there is not adequate rainfall. Monitor for secondary pests and apply protective treatments to susceptible trees for lethal invaders such as borers. Fertilizer and soil amendments should be applied according to soil or foliar nutrient analysis test results. Root Invigoration should be performed to promote root regeneration and a better environment for remaining roots. At a minimum, mulch should be applied to reduce soil moisture loss and promote root growth.

Founded in 1926, The Bartlett Tree Research Laboratories is the research wing of Bartlett Tree Experts. Scientists here develop guidelines for all of the Company’s services. The Lab also houses a state-of-the-art plant diagnostic clinic and provides vital technical support to Bartlett arborists and field staff.