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Squirrels & Wildlife

Are Groundhogs Bad for Your Backyard? Burrows Are the Issue

Garden damage is real but modest; the burrow under a shed, deck or retaining wall is the expensive part. How to judge which you have.

By Zakaria 2 min read Save to Pinterest — opens Pinterest in a new tab
A groundhog sitting upright on its haunches, feeding with both forepaws
Photo: Trek_Jason, Pixabay Content License, via Pixabay
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A groundhog eating the beans is a fencing problem. A groundhog excavating a cubic metre of soil under the shed is a different one, and the second is what makes them worth taking seriously.

Which problem do you have

signproblem
Clipped bean and pea tops, stripped lettucegrazing — fence it
Squash flowers gone, young fruit bittengrazing
25–30 cm hole with a soil fanburrow
Hole against a shed base, deck or wallstructural — act now
Settling paving or a step droppingundermining already happening

A fence that works

elementspecification
Height above ground90 cm minimum
Buried depth30 cm
Apronturned outward, 30 cm, L-shaped
Top 30 cmleft unattached so it bends
Meshwelded wire, 25–50 mm

Never seal a burrow without checking for occupants

Dependent young are in the chamber in late spring. Sealing then buries them. Watch the entrance, or loosely plug it with crumpled paper and see whether it is pushed out over two or three days before doing anything permanent.

What does not work

  • Ultrasonic devices — no evidence of any effect
  • Mothballs — ineffective outdoors, and illegal to use this way in many jurisdictions
  • Predator urine products — inconsistent at best, and habituated to quickly
  • Smoke or flooding a burrow — dangerous, often illegal, and the system has other exits
  • Filling alone, without removing cover and food, which just gets re-dug

Do the structural one first

If there is a burrow against a foundation, shed base or retaining wall, that takes priority over the vegetable patch. Exclusion there is cheaper than the settlement it prevents, and the animal is easier to move before it has overwintered in place.

Common questions

Are groundhogs actually harmful in a garden?

Two separate questions. As grazers they eat beans, peas, lettuce, brassicas, squash flowers and young fruit, which is annoying and fixable with a fence. As burrowers they excavate systems of several metres with multiple entrances, and when one of those runs under a shed, deck, patio, retaining wall or house footing, the undermining is the real cost. Most complaints are about the first; most expense comes from the second.

How much soil does a burrow move?

A main burrow can be 3 to 10 metres long with two to five entrances and a chamber a metre or more down, and the excavated spoil commonly runs to a cubic metre or more. Under a slab or a shallow footing that is a void, and voids under structures settle. The telltale is a 25–30 cm entrance hole with a fan of fresh earth beside it.

Will a fence keep them out?

Only a fence built for a digger. Wire mesh at least 90 cm high, with the bottom 30 cm buried and turned outward into an L-shaped apron, and the top 30 cm left unattached so it bends under the weight of a climbing animal. Groundhogs both dig and climb, so a fence that addresses only one gets beaten by the other.

Are groundhogs dangerous?

Not to people in any ordinary sense. They avoid humans, flee to the burrow, and only bite when cornered or handled. They can carry rabies but rarely do. The genuine hazards are structural — an undermined wall or step — and a burrow entrance in a paddock or lawn that a horse or a person can step into.

What actually deters them?

Removing cover and food first: clear brush piles, long grass and woodpiles near the vegetable garden, and fence the beds properly. Beyond that, filling and monitoring burrows during the active season sometimes moves an animal on. Repellents, ultrasonic devices and mothballs have no reliable effect, and mothballs used outdoors are both ineffective and illegal in many places.

Is there a season when this is easier?

Yes — groundhogs are true hibernators and are underground from roughly October to February or March. Exclusion work and burrow filling near structures is best done in autumn before hibernation or in spring, and never in late spring when there are dependent young in the chamber. Check for activity before sealing anything.

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