Fight cedar roots with cedar!

May 19, 2024
During spring of 2016 we installed 3 raised bed grow boxes that would hold 9 tomato plants each. The location was in close proximity to a 3’ diameter western cedar tree which has roots radiating out well beyond the location of our raised beds. So to prevent intrusion of the cedar roots, we elevated the beds above ground level using bricks pillars to support the roofing material on which our soil would be supported inside of the wooden walls of the box. The design concept was to create a 3” air gap under the raised bed. This, we reasoned, would be enough to prevent the intrusion of the roots of the cedar tree. For many years this concept was very effective and no cedar roots were able to penetrate into the growing beds; however, this spring as I began to dig out the beds to replace the growing medium with a fresh soil @ compost mix, I noticed cedar roots in two of the three beds. As I examined the path the roots had taken, I discovered there had been a soil connection where the roots were able to grow thru the perimeter drain holes I had allowed. My error in the original construction had allowed enough soil to get underneath the boxes for the pesky cedar roots to find their pathway into the boxes.
So this week after understanding how this occurred I elevated the two boxes an additional brick higher off the ground and I created a 1’ space around each box. I removed all cedar roots and soil from the space around the bottom of the boxes and stuffed this empty space with green cedar foliage and cedar wood creating the walkways around the boxes consisting of no soil but instead a 6” thick mat of cedar bows.
I am hopeful that this reconstruction of my air gaps will endure many more years of successful Tomato growing space! With 8 years of testing our air gap strategy worked very well with a minor flaw that allowed roots access via a soil path to invade. So if you have a situation of invasive roots, try creating an air gap! Just be creative to avoid allowing a soil pathway into your grow box! A fun project.

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Nice! Let us know in another 8 years how it went!

I’ll tell you… roots just love finding the water source. True story… basement bathroom had a leak around the base of the toilet (over tile over slab) when it was flushed. Hmmm… must need a new wax ring. Pulled the toilet to find a 1/4" tree root that worked up between toilet flange and concrete… through wax ring, and back down into the main line. Crazy what roots will do to find water!

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