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Construction Damage to Douglas Fir Roots: Assess and Act

Excavation Near an 80-Year-Old Douglas Fir: How Bad Is It?

New construction dug 12–18 inches deep near your property-line Douglas fir, severing finger-sized roots on roughly half the root zone circumference. Six years ago a trench 5 feet away caused no decline. Conifers tolerate root loss better than hardwoods due to a deep taproot, but losing ~50% of feeder roots (in the top 6–12 inches) often causes delayed dieback, especially during drought.

Options

If the tree is on the neighbor’s lot: Agree in writing that they’ll cover removal if it dies.
If it’s yours: Fertilize with 10-10-10 at 1 lb per inch trunk diameter, scattered and watered in (before rain). Repeat this winter and next spring to stimulate root regeneration.
Lean toward removal now if the construction company will pay—given the damage extent and limited rooting space on the driveway side, decline is probable.

Monitor for canopy thinning next growing season.

Trees: Cutting One Pine Root for a Deck Foundation: Is It Safe?; Cutting Douglas Fir Roots for a Road: Stability and Health Risks; Cottonwood Exposed Root Rot: Cover with Sand, Fertilize; Tree Root Damage from Neighbor's Excavation: Risks to Spruce and Foundation; Douglas Fir: Adding Soil Over Roots—2″ Max, Use Sand; Douglas Fir Root System: Depth, Spread, and Excavation Safety; Douglas Fir Root Damage from Driveway: Recovery Timeline; Protecting Tree Roots During Construction Near Lime Trees; Douglas Fir Root Cutting Risks: Protecting a Giant on a Slope; Assessing Root Damage and Grade Changes Around Douglas Fir

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