American Grove
Tree vs. Sidewalk - To Install Root Barriers or Not?
Our Village Council recently approved a sidewalk replacement project for spring 2012. The contractor was asked to include root barriers in the bid. The information I have found on root barriers is at best conflicting.
In your experience, what root pruning / barrier techniques have had the most positive outcomes? Can you provide any specifications for your methods &/or materials used?
As a Tree City USA, we always try to keep an eye out for best practices to preserve our mature street trees.
Thank you in advance for your assistance.
Comment
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Comment by Jamie Kirby on February 6, 2012 at 12:59pm -
Interesting topic. When asked the same question, I haven't found any definitive evidence to lead me to a confident recommendation. I did come across this abstract, which gave me some good information to share with folks who are faced with making a decision: http://ucrturf.ucr.edu/publications/Field%20Day%20Procs/1999%20Proc.... It is very short, and explains in simple language how tricky this topic really is.
Another good article published in Arboriculture & Urban Forestry a while back is at http://joa.isa-arbor.com/request.asp?JournalID=1&ArticleID=3034.... Perhaps you read these same documents when you were doing your research, but I thought it would be worth sharing. Good luck and keep us posted on your project!
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Comment by Neil Norton on February 6, 2012 at 11:32am -
Hi Lisa, I recommend reading James Urban's Up By The Roots. This topic can get quite detailed and that is a great resource on all 3 methods. All 3 methods are used to increase soil volume for maximum root growth. Each method has its application depending on the site and budget. Below are additional resources;
Root Bridging: Great example of root bridging is in the short video, Common Ground Through Arborcultural Practices. Basically it is when you provide a subterranean pathway for the roots to pass through to an area where they can expand. Some use Silvacells to create the pathway.
More on SilvaCells at Deep Root.
From Wikipedia: Structural Soil is a medium that can be compacted to pavement design and installation requirements while permitting root growth. It is a mixture of gap-graded gravels (made of crushed stone), clay loam, and a hydrogel stabilizing agent to keep the mixture from separating. It provides an integrated, root penetrable, high strength pavement system that shifts design away from individual tree pits.
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Comment by Lisa Segard on February 6, 2012 at 9:45am -
What is structural soil, root bridging &/or silva cell, how do they differ & where can they be found?
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Comment by Jim Mitchell on February 2, 2012 at 1:56pm
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We use strucural soil when we can get it approved. Our oldest project is 8 yrs and no issues.The storm water angle seems to grab attention, perhaps due to new reg's in MO. Believe me we are constantly battleing the "engineers"
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Comment by Neil Norton on February 2, 2012 at 11:22am
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Good questions. In my local city we have found root barriers to compromise long term health and size of street trees. They also provide a false sense of effectiveness as they are often compromised through time due to improper installation. The best solution is use structural soil, root bridging or silva cell to maximize root growth. The issue here is cost, it is definitely more expensive to plant a tree using these technologies. However, the benefits, particularly stormwater benefits associated with a larger canopy can easily be offset over the long term. The trick is invest at the front end but that can be difficult during these economic times, moreover, often it is the responsibility of the land owner which is not always the City. That said the Future Value of the Investment using root maximization technologies definitely offsets the lower up front investment of root barriers.
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