We talk a lot about what new things to create and plant, but, we need to talk a bit about protecting what already exists. Since large trees are beneficial in terms of cleaning the air and cooling the environment, taking extra care around them is extremely important.

Much of this information seems obvious, yet as a trade, we keep making the same mistakes over and over again. I’m rather hoping that those who do get it will pass the word on to colleagues. When we’re working around trees, we must protect the root zone. Ideally, this means staying off it, or at least protecting it from compaction.

Tree roots extend much farther than we used to think. The best visualization I’ve heard so far is of a wine glass on a dinner plate, so we should stay much farther from the trunk than is often recommended. It’s in our nature to push envelopes, so making barriers strong is important. A snow fence is flexible and easily pushed in or knocked over. Plywood mounted on t-bars is much better. An operator on a skid steer will shy away from plywood more than flexible fencing.

Simple, effective measures
Recently we arrived on a jobsite which had already been worked on during the expansion of a residence. For a year, skid steers had been driving over the root zone of a columnar oak. The tree still looks fine … and it will for a while. Often we think that since a tree does not suffer immediately, we didn’t do any damage, so next time we do things the same way. The thing is, an organism that lives on a 400-year timeline, dies on a 400-year timeline. It may be ten years before the tree dies. It will show decline first at the crown, and die further down every year.

Since we arrived on the job, we have laid plywood over the root zone to prevent further compaction. The path into the back yard is very restricted — maybe three metres maximum — so there are no options other than passing close to the oak. Laying plywood helps spread the weight over a larger area, reducing compaction. When we are finished with construction, we will lay an eight-inch layer of composted pine mulch over the root zone to allow Mother Nature to aerate the soil. The mulch encourages beneficial fungi and soil organisms to work into the soil and open it up, and re-establishes the mycorrhizae. It also allows better water filtration. A thick application of rich compost is, according to Dr. Alex Shigo, the best way to help the health of any stressed tree.

Many landscapers don’t think twice about installing an interlock drive or pathway within the root zone of a tree. This devastates the tree. A 200-year-old oak in Milton, Ont., is dying from an interlock driveway installed ten years ago. The tree is now a liability. Its dead branches are bigger than most trees, and put many people in danger. The original driveway was gravel. It may have been possible to go against protocol, and build on top of the existing gravel, without excavating. As long as the customer was educated, this should be an acceptable method in order to save the tree.

Another problem is soil storage during construction. Piling soil on a root zone for extended periods during construction can harm the tree by suffocating the roots, just as raising the grade more than six inches will suffocate them.

Do it right now, and later
I once watched a local nursery crew do everything right. They were putting in a parking lot and lowering the grade. They carefully excavated far out from the drip line and built a stone retaining wall. They left the existing meadow cover under the canopy. It was perfect. Then a few years later, someone decided to plant annuals, stripped the meadow, rototilled the soil deeply and planted it up with annuals. Now, every leaf that falls is cleaned up, and every year the soil is tilled, doing extreme harm to the roots.

We can learn to live within the health and environment of the tree. We can keep its value and environmental benefits. We can enjoy the birds and butterflies it attracts. We can set ourselves apart from competitors, who do not appreciate and care for the trees — and we can be profitable doing it. Give it a shot if you don’t already.

           Sean James is owner of an Ontario-based environmentally-conscious landscape design/build/maintenance company.