How to remove tree roots after the tree is gone (and when to leave them)

What happens to tree roots after the tree is cut down?

A stump grinder takes out the stump and the top of the root flare and leaves the side roots in the soil to decay, which is normal practice; the hub on stump grinding in Washington and Oregon covers the grind itself, the grindings and replanting. This page is about everything left underneath.

There is more of it than people expect. Oregon State University Extension says most of a tree’s roots are in the top 18 inches of soil, and the International Society of Arboriculture says roots commonly spread many times the width of the crown and can reach farther out than the tree was tall. A root you hit while digging a bed 30 feet from the old trunk can still be from that tree.

Dead roots in moist soil are what decay fungi need: the Forest Service’s Wood Handbook says serious decay happens only in wood wetter than about 30 percent moisture, and wood kept air dry does not decay. Big conifer roots go slowly, and some carry disease. The Oregon Department of Forestry says the laminated root rot fungus can survive for decades in large old stumps or roots and infects new trees whose roots touch them; on those sites it advises removing the stumps and roots before replanting a susceptible conifer, or planting resistant conifers or immune hardwoods instead.

Will tree roots grow back? The species that sucker

For a Douglas fir, no: the Forest Service’s silvics manual says Douglas fir does not naturally reproduce vegetatively, so its roots simply die. For some broadleaf trees, the roots are the whole problem. In quaking aspen, the Forest Service’s species review explains that the stem sends a hormone down that holds root buds back; cut the stem and the buds grow. It reports 20,000 to 30,000 suckers per acre as typical in aspen stands the first year after the top is killed, and in a Utah and Wyoming study it cites, 70 percent of suckers came from roots within about 3 inches of the surface.

Sources: USDA Forest Service Fire Effects Information System species reviews; Silvics of North America; King County Noxious Weed Control Program; checked 2026-10-02. USDA status is the national nativity field in the Forest Service’s FIADB plant reference records, where every species listed is recorded in both Washington and Oregon; for black locust, the FEIS review places its native range in the eastern U.S. and notes planted groves spreading into old fields in eastern Washington.

If the tree was a sucker species, removing the stump does not end it, and shoots can come up across the lawn. King County’s advice for laurel is to dig out the stump with as much root as possible and keep cutting new shoots. Bigleaf maple is different: it comes back from the root crown, so grinding below the crown matters more than chasing its roots; how to remove a tree stump compares the ways to deal with the crown itself.

Your options: leave the roots, grind them, dig them or kill the suckers

Sources: Oregon Department of Forestry; WSU Puyallup, Wood chip mulch; Pacific Northwest Weed Management Handbook; King County Noxious Weed Control Program; checked 2026-10-02.

Grinding along surface roots is the add-on the stump grinding cost page calls root chasing: worth it where roots lift a walk, a waste where they will rot under the grass. For suckers, King County’s laurel guidance shows what persistence looks like: cut new stems regularly through the growing season, over several years. A herbicide shortens that only if its label covers the use; “the label is the law,” as EPA puts it, and how to kill a tree stump covers products and timing. A stump remover will not help here; it is made for dead wood, as stump remover chemicals explains.

How to dig out tree roots

Dig only where the roots are in the way, and start with the paperwork. In both states, owner digging is exempt from the locate law only when it stays less than 12 inches deep (RCW 19.122.031 in Washington; OAR 952-001-0050 in Oregon), and digging out roots usually goes deeper than that.

1. Request the locateCall 811 at least two full business days ahead (Washington allows up to 10; Oregon’s center asks for no more than 10), and hand-dig near the marks.
2. Expose the rootShovel along it and wash the soil off with a hose so you can see where it runs and how thick it is.
3. Check where it leadsIf it runs toward a living tree you want to keep, stop and read the next section before cutting anything over 4 inches thick.
4. Cut it cleanlyUse a pruning saw, loppers or the blade of a mattock; OSU’s guidance is sharp, clean cuts.
5. Lever it outPry the cut section free with a digging bar and keep following it until the space you need is clear.
6. Backfill with soilNot chips or grindings: WSU’s Linda Chalker-Scott writes that wood mulch should never be used as backfill.

How deep to go depends on what goes on top. For building or paving over an old stump, Family Handyman’s rule is to take the wood out as deep as the stump was wide; the person designing the patio or footing should confirm what the base needs. After a grind, the same logic applies to the grindings: rake them out of a spot you want to replant and use them as mulch elsewhere. The difference between grinding and pulling the whole root ball is laid out in stump removal vs grinding.

Protecting the roots of trees you keep

Cutting a dead tree’s roots is a cleanup job. Cutting a living tree’s roots can make it fall over. OSU Extension, following ISA, sets a tree’s critical root zone at 1 foot of radius for every inch of trunk diameter measured at 4.5 feet, says about 85 percent of the root mass sits inside it, and says not to cut roots more than 4 inches thick because they are structural. For utility lines, OSU says to tunnel at least 18 inches under that zone rather than trench through it.

The Forest Service’s tree risk manual uses a wider circle, 1.5 feet per inch of trunk diameter, and says up to 40 percent of the roots inside it can be damaged before the tree’s anchoring is seriously impaired, less for sensitive species. For a maple 20 inches thick at chest height next to the old stump, that puts the zone to keep cuts out of at 20 to 30 feet from its trunk. ISA’s construction brochure adds the practical step: an arborist can prune roots out of the way before excavation, or cut them cleanly before anything tears them. Surface roots of trees you keep are a separate topic, covered in tree roots above ground.

Permits for cutting roots

Portland’s tree code applies its technical specifications to all regulated trees in the city (PCC 11.60.010). Root cutting must follow proper arboricultural practice with clean, sharp tools, and no tree may be excessively pruned (PCC 11.60.040); the code’s definitions count removing 25 percent or more of the functioning root area in one growing season as excessive pruning, and trenching or excavating inside the root protection zone, 1 foot per inch of diameter, as injury (PCC 11.80.020). Street trees need a city pruning permit, Portland issues a separate street tree root pruning permit, and its guidance says root pruning should be done only by professional arborists or after consulting a City arborist.

In Seattle, paid work that prunes or removes live roots 2 inches or more in diameter is “reportable work” under the tree protection code, SMC 25.11; a registered tree service provider must post a public notice on SDCI’s website at least three full business days before starting. Other cities are listed in tree removal permits in Washington and tree removal permits in Oregon. Roots that belong to a neighbor’s tree raise property questions too; see Washington neighbor tree law or Oregon neighbor tree law. Not legal advice.

Do tree roots break sewer pipes and foundations?

In ISA’s account, roots get into pipes that already leak. Its utility brochure says new steel and PVC water and sewer lines are generally resistant to root damage, while older cement, clay or cast-iron pipes can degrade and leak; the moisture draws roots in, and they widen the cracks. Removing roots from the yard does not repair the pipe.

Who owns the sewer lateral, what cities require for sidewalk heave and what is known about foundations are covered in tree root damage on your property; this page does not repeat them.