How To Dig Around & Trench Through Tree Roots

In our landscape, trees remain a constant comfort. After all, they’ve been there for years, decades or even centuries.

That, of course, means trees don’t budge, even when we may need them to. If you’re starting a construction project, like installing a fence or irrigation system, tree roots can be a challenge.

Lacretia, a Davey blog reader, recently asked, “How can I dig a 3-foot deep trench line near my 100-year-old oak without damaging it?” Below, read the best way to go about this and learn when it’s likely not a good idea to trench through tree roots.

The Best Approach For Digging A Ditch Around Tree Roots

Digging a trench around a tree or through tree roots takes a lot of planning, a little math and some help from your arborist.

How Do I Go About Protecting Tree Roots During Construction?

Ideally, trees should be healthy and in good shape before you begin a construction project. In other words, the roots should be well-watered, the canopy free of any dead or diseased branches and the soil stocked with nutrients.

You should also prepare the construction site by checking for any underground utility lines. Contact your utility company, and they’ll help point these out.

What Are The Guidelines For Digging A Ditch Around Tree Roots?

Tree roots spread much further than what we can see above ground. Whenever possible, it’s best to start digging as far away from your tree as possible.

If you want a more exact distance, try this!

1. Measure the diameter of your tree. Wrap a measuring tape around the tree four and a half feet from the tree’s base. Divide that measurement (the tree’s circumference) by 3.14 to get the diameter.
2. Multiply the tree’s diameter by 5. That number is the minimum safe distance away from the tree to dig to avoid cutting critical structural roots.
3. For example, if your maple tree has a diameter of 2 feet, avoid any digging within 10 feet of the tree in all directions.

Is It Safe To CutThrough Tree Roots?

Digging through and cutting tree roots isn’t something to take lightly. Cutting critical roots can interrupt the tree’s water and nutrient uptake, leave permanent damage to the tree's structure and stability, or, in the worst case, cause the tree to die.

Before attempting to cut tree roots, talk to your arborist about what may or may not be safe for your tree. Your arborist can prune the roots for you, or you can follow our step-by-step guidelines for DIY root cutting. Remember, proceed with caution!

Your arborist might also be able to dig a trench for utilities using an air tool which will remove soil without damaging roots. S/he might also be able to recommend directional drilling or other methods of installing utilities without trenching. Special procedures may be needed to protect your valuable trees.

Here are things to consider for new construction landscaping.