Key takeaways
- Roots commonly spread many times the width of the crown, so a trench that looks far from the trunk can still cut major roots.
- Piling fill soil over roots can suffocate them, so ask an arborist before changing grade.
- An arborist can prune roots cleanly before excavation, which is better than a backhoe tearing them.
- Call 811 before you dig. Locating underground utilities before digging is often required by law.
Sprinkler lines, new utilities, a patio, a retaining wall: ordinary yard projects mean digging next to trees. The tree does not complain until it is too late.
Why is trenching near a tree a problem?
The ISA says roots commonly spread many times the breadth of the tree crown and can reach farther than the tree is tall. The part of the root zone essential for health and stability can be well outside the branch spread, so the question is never just how close the trench is to the trunk. The ISA lists trenching, grading, paving, drainage changes and adding or removing soil as the main root-damaging activities.
Its mature tree care brochure goes further: trenching or earthmoving inside the root zone can cause more harm than good.
What is the least harmful way to dig?
Where a utility has to be installed, the ISA says planning can reroute lines or tunnel them under roots. When a utility needs repair or replacement, excavation can damage roots and even kill the tree, so it helps to design around that from the start.
If roots must be cut, an arborist can prune them out of the way before excavation or cut them cleanly before any damage is done. A clean cut is better for a tree than a root torn by a bucket. Ask the contractor whether tunneling or hand digging near the trunk is an option for your job.
What about adding or removing soil?
Raising the grade is a quiet way to hurt a tree. The ISA's turf brochure warns that fill soil added around existing mature trees can reduce soil oxygen and suffocate roots, and says to consult an ISA Certified Arborist before adding soil over tree roots. Removing soil can strip the fine roots that sit in the upper layers. The ISA says the majority of fine, water-absorbing roots are in the top 6 inches of soil.
If a patio or yard plan changes grade near a tree, ask for an arborist's opinion before the plan is final. See protecting trees during construction.
Do I need to call 811 first?
Yes, before any digging. The ISA says accidental digging into underground utilities can interrupt service or result in injury or loss of life, and that locating utilities before digging is often required by law. Never assume utilities are buried deeper than you plan to dig. Our guide to calling 811 before stump grinding covers the same call.
In Reno, the Truckee Meadows Water Authority notes that anyone working within 10 feet of a publicly owned tree must contact the City's Urban Forester before digging.
How can Battle Born help?
An arborist consultation before the digging is the cheapest time to learn which roots matter. If a tree has to come out for a project, we do removal, stump grinding and lot clearing with our own equipment. Call 775.232.8243 for a free estimate.
Sources
- International Society of Arboriculture, Trees Are Good: Avoiding Tree Damage During Construction (brochure) (read October 17, 2026)
- International Society of Arboriculture, Trees Are Good: Trees and Turf (brochure) (read October 17, 2026)
- International Society of Arboriculture, Trees Are Good: Mature Tree Care (brochure) (read October 17, 2026)
- International Society of Arboriculture, Trees Are Good: Avoiding Tree and Utility Conflicts (brochure) (read October 17, 2026)