Holes Around Tree Roots: Squirrels, Voles, or Wasps?

Holes at the base of a tree usually belong to squirrels burying and retrieving nuts, voles working the mulch line, or rats denning in the sheltered pocket under the root flare — and sometimes to nothing living at all, since decayed old roots leave open channels in the soil. The one to identify before you get close is a yellowjacket colony nesting in a hollow among the roots.

Most likely causes

  • Squirrels — shallow 2-inch cache divots scattered around the drip line
  • Voles — inch-wide holes and runways in the mulch ring, with gnawed bark at the trunk base
  • Rats — a worn 2- to 3-inch burrow angling under the root flare
  • Decayed root channels — clean holes that trace the path of a rotted-away root
  • Yellowjackets — a busy opening among the roots with steady wasp traffic

Compare the possible causes

Possible cause Key signs When it happens How likely
Squirrels caching and retrieving nuts Shallow divots 1 to 3 inches wide and a couple of inches deep, scattered loosely around the tree, often with nut shells or husks nearby Heaviest in fall (burying) and late winter into spring (digging caches back up) Very common
Voles in the mulch ring Inch-wide openings at the mulch line connected by worn surface trails, and — the serious part — bark gnawed off in a band at the trunk base Year-round, with damage concentrated under winter snow and revealed in early spring Common
Rats denning under the root flare A single well-worn burrow 2 to 3 inches across diving under a major root, with kicked-out soil, smooth edges, and possibly droppings Any season; more likely near bird feeders, compost, water sources, or outbuildings Less common
Decayed root channels Clean, smooth-walled holes with no excavated soil, no wear, and no traffic, sometimes following a straight line away from the trunk Appear gradually, often noticed after rain washes them open Common
Yellowjackets nesting in a root cavity A hole among the roots with insects flying in and out in a steady stream, especially on warm afternoons Colonies grow through summer and peak in August and September Less common

Visual clues to check

  • Stand back for two minutes and watch the hole: steady insect traffic means wasps — stop the inspection there
  • Count and pattern: many shallow scattered divots point to squirrels; one deep worn hole points to a resident
  • Pull mulch gently away from the trunk and check the bark at soil level for gnawing — the vole tell
  • Look at the soil: no excavated dirt suggests a decayed root channel or squirrel divot; a heaped fan suggests rats
  • Note the angle: cache divots are shallow scoops; burrows dive under the root flare and keep going
  • Check for nut shells, husk fragments, or small chewed cones — squirrel litter that dates the digging

The causes in detail

Squirrels caching and retrieving nuts

The soft, mulched, root-riddled ground under a tree is a squirrel's filing cabinet. Each divot is a single nut deposit or withdrawal — quick, shallow, abandoned immediately. Under oaks, hickories, and walnuts the ground can look peppered by November. It's untidy but genuinely harmless to an established tree, and the holes rake flat in minutes.

Voles in the mulch ring

A deep mulch ring piled against a trunk (the 'mulch volcano') gives voles food, cover, and tunneling medium in one package. They open small holes through the mulch, run trails around the tree, and gnaw the nutrient-rich inner bark at the base — a complete ring of gnawing girdles and kills the tree. Young fruit trees and thin-barked ornamentals are the usual victims. The holes are the warning; the bark is the stakes.

Rats denning under the root flare

The cavity beneath a big root flare is structurally perfect for a rat burrow — a hard roof no shovel or predator easily breaches. A rat hole here shows the usual signatures: heaped excavated soil, an entrance polished by nightly traffic, and greasy rub marks where fur repeatedly touches the root. One burrow under a yard tree often connects to food sources nearby, so treat it as part of a bigger picture rather than an isolated hole.

Decayed root channels

When a tree loses a major root — or after an old stump's roots rot away nearby — the decayed wood leaves a hollow tube in the soil that eventually opens to the surface. These 'ghost roots' explain many mystery holes around older trees: nothing dug them, nothing lives in them, and they trace the old root's path. They're harmless, though multiple large collapsing channels around a declining tree are worth mentioning to an arborist as a sign of root loss.

Yellowjackets nesting in a root cavity

Yellowjackets readily take over rodent burrows and hollows in root systems, and by late summer a colony can number in the thousands. The visual is unmistakable once you look for it: constant one-in, one-out traffic at a single opening. Mower and string-trimmer vibration is a classic trigger for mass stings, which is why identifying this before yard work matters. Observe from well back; this one is not a judgment call.

When to worry

  • Any hole with continuous wasp traffic within reach of play areas, patios, or the mowing route
  • Bark gnawed partway or fully around the trunk base — girdling is an emergency for young trees
  • A worn burrow under the roots plus droppings or rub marks, especially within 100 feet of the house
  • Multiple large soil openings around a mature tree that's also thinning in the canopy — possible root decay
  • Soil around the root flare sinking or the tree developing a new lean after wet weather

What to do now

  1. Do the two-minute traffic check from a distance before any close inspection or mowing near the hole
  2. Rake squirrel divots flat and reseed thin patches; no other response is needed
  3. Fix the mulch: pull it back to leave 3 to 6 inches of bare ground around the trunk, and keep the layer under 3 inches deep
  4. Protect young trees from voles with a cylinder of quarter-inch hardware cloth around the base, sunk an inch or two into the soil
  5. For a suspected rat burrow, remove nearby food sources and bring in a licensed pest professional to confirm and treat
  6. Mark a yellowjacket opening from a distance, keep everyone away, and have a licensed pest control operator handle it — ground nests near trees are their everyday work
  7. Ask a certified arborist to evaluate the tree if holes coincide with canopy dieback, fungus at the base, or a new lean

What not to do

  • Don't pour boiling water, gasoline, or insecticide into holes among roots — you'll damage the tree's root system along with whatever you're aiming at
  • Don't plug a hole with active insect traffic; blocked yellowjackets pour out of secondary exits, sometimes hundreds at once
  • Don't run a mower or trimmer over a suspected nest opening — vibration is the most common sting trigger
  • Don't pile mulch back against the trunk to 'cover the holes'; you're rebuilding vole habitat
  • Don't excavate around the root flare with a shovel to chase a burrow; severing roots does more harm than the digger did

Think you know the suspect?

These animals commonly cause this clue — see their full sign profiles:

Frequently asked questions

Why are there holes at the base of my tree with no dirt around them?

Soil-free holes at a tree base are usually either squirrel cache divots — quick scoops with the soil flicked aside — or channels left behind where an old root rotted away. Decayed root channels are the classic 'nothing dug this' answer: smooth, clean tubes tracing the old root's path, with no traffic and no fresh digging.

Can animals digging around roots hurt the tree?

Squirrel caching and even rat burrows rarely harm an established tree — the root system is far bigger than the disturbance. The real threat is voles gnawing bark at the trunk base: a full ring of chewed bark girdles the tree and can kill it, and young or thin-barked trees can be lost in a single winter.

How do I know if wasps are living in a hole by my tree?

Watch from 15 to 20 feet away for a few minutes on a warm afternoon. An active yellowjacket nest shows constant traffic — insects entering and leaving the same opening every few seconds. No traffic on a warm day usually means no active colony, but check again before mowing, since activity varies through the day.

Should I fill in holes around tree roots?

Fill them once you know they're inactive and insect-free. Use plain topsoil, firm it gently by hand rather than stomping over roots, and skip concrete or gravel, which trap moisture against roots. If a hole reopens within days, something is using it — identify the occupant before filling again.

Related yard clues

Yard Holes Small Holes in Yard With No Mound: What's Digging? Small holes in your yard with no dirt mound are usually caused by squirrels, chipmunks, foraging birds, earthworms, or ground-nesting insects. The size of the hole, how deep it goes, the time of year, and whether the damage appeared overnight can narrow down the cause quickly. Read the guide → Yard Holes Two-Inch Holes in Yard: Chipmunk, Rat, or Something Else? A round hole about two inches across is classic burrow size, and the usual suspects are chipmunks, rats, and thirteen-lined ground squirrels. Chipmunk holes are clean with no soil pile, rat holes are worn and hug structures, and ground squirrel holes sit in open, sunny lawn — those three clues sort out most cases. Read the guide → Yard Holes Quarter-Size Holes in Yard: Wasps, Cicadas, or Voles? Holes about the size of a quarter — roughly an inch across — most often belong to cicada killer wasps, emerging cicadas, ground-nesting bees, or voles. The soil is the fastest clue: a big horseshoe of excavated dirt means a cicada killer, a clean hole with no soil means a cicada came out of it, and a small crumbly rim means bees. Watch briefly from a distance before getting close, in case wasps own it. Read the guide → Yard Holes Holes in Mulch Beds: Who's Digging Through Your Mulch? Disturbed mulch usually comes down to a simple distinction: mulch flipped and scattered on top means squirrels or birds foraging through it, while an actual hole punched down into the soil beneath means a chipmunk, rat, or cat. Squirrels and chipmunks are the everyday culprits; the pattern of the mess tells you whether you're looking at snacking, caching, burrowing, or a litter box. Read the guide →

Still not sure? Compare with these clues

Plant Damage Bark Stripped From Trees: Squirrels, Deer, Voles, or Birds? The height of the damage tells you the most: bark gnawed at ground level is usually voles or rabbits, shredded bark from 1 to 4 feet up is deer rubbing their antlers, and stripped patches on upper branches point to squirrels. Neat horizontal rows of shallow holes are a sapsucker's work — and any damage that circles the whole trunk (girdling) puts the tree at real risk. Read the guide → Mushrooms & Growths Shelf Fungus on a Tree Trunk: A Sign of Decay Inside the Tree A shelf or bracket fungus growing from a living tree's trunk is a red flag: it means the fungus has been decaying wood inside the tree, often for years, before producing that visible 'conk.' The tree may still look healthy, but internal decay weakens its structure — so the right move is an assessment by an ISA-certified arborist, not knocking the fungus off. Read the guide → Yard Holes Tunnels in Grass: Mole or Vole? How to Tell in Seconds Tunnels in a lawn come in two distinct styles: raised, spongy ridges you can feel underfoot are mole feeding tunnels just below the surface, while flat, worn trails clipped into the grass itself are vole runways. Moles hunt worms and grubs under your turf; voles eat the grass and bark on top of it — so telling them apart decides everything about what to do next. Read the guide →