Fumigant cartridges designed specifically for burrowing rodents are the most direct thing you can place inside a groundhog hole to drive out or kill the animal. But groundhog burrows are complex tunnel systems with multiple exits, which means stuffing something down one hole rarely solves the problem on its own. Repellents, gas cartridges, and home remedies all have different success rates, and the approach that works best depends on your property, local laws, and how many burrows you are dealing with.
How Groundhog Burrows Actually Work
Before you put anything in a groundhog hole, it helps to understand what you are dealing with underground. A single groundhog burrow can stretch 25 to 30 feet long and sit two to five feet below the surface. Most burrows have at least two openings and sometimes as many as five. The main entrance is usually obvious, marked by a mound of freshly dug dirt. But escape holes are harder to spot because groundhogs push the dirt outward and often conceal the opening under brush or along a foundation. If you treat only the main entrance, the groundhog simply leaves through a back door you never noticed.
This multi-exit design is the single biggest reason why “just pour something down the hole” fails more often than people expect. Any treatment that relies on fumes or odor needs all exits sealed except the one you are treating, or the animal escapes and returns once the irritant fades. Before applying anything, walk the area within about 20 feet of the main entrance and look for secondary holes, usually two to three inches across and often partially hidden by vegetation.
Fumigant Cartridges
Commercial gas cartridges, sometimes called rodent bombs, are the most commonly recommended product for direct burrow treatment. These are small cardboard or wax tubes filled with a compound that, when lit and placed inside the burrow, releases carbon dioxide and carbon monoxide as it smolders. The gases fill the tunnel system, and if the burrow is properly sealed, the groundhog is killed underground. You can find these at most farm supply stores, and they are labeled for use on woodchucks (the formal name for groundhogs) as well as other burrowing pests.
The process is straightforward but has a few non-negotiable steps. You light the cartridge, place it as far into the main tunnel as you can reach, then immediately seal that entrance with packed soil or sod. Every other opening you have found must already be sealed before you ignite the cartridge. If you miss even one exit hole, the fumes dissipate too quickly and the groundhog escapes. Timing matters too. Fumigating in early morning or late afternoon, when groundhogs are most likely to be inside the burrow, improves your chances considerably compared to midday treatment when the animal may be out foraging.
A critical safety note: never use fumigant cartridges in burrows that run under or near buildings, porches, sheds, or decks. The smoldering cartridge can ignite dry wood, insulation, or debris, and the gases can seep into enclosed spaces where people or pets are present. If the groundhog’s burrow runs under a structure, fumigation is off the table and you need a different approach entirely.
Ammonia and Other Home Remedies
Ammonia-soaked rags stuffed into groundhog holes are probably the most frequently suggested home remedy online. The idea is that the strong odor irritates the animal’s sensitive nose and drives it out. In practice, ammonia fumes dissipate quickly outdoors, especially in a tunnel system with airflow between multiple openings. You would need to re-soak and replace the rags every day or two, and even then, many groundhogs simply tolerate the smell or avoid that particular tunnel entrance while continuing to use the burrow through other exits.
Other home remedies you will encounter include mothballs (naphthalene), Epsom salts, cayenne pepper, and garlic. Mothballs are a poor choice for several reasons. The amount needed to produce a meaningful concentration of naphthalene vapor in a tunnel system is far more than what you would use in a closet, and naphthalene is toxic to pets, children, and soil organisms. In many states, using mothballs outdoors as a pesticide is actually a violation of federal label law, since they are only registered for use in enclosed containers for fabric protection. Cayenne pepper and garlic may cause mild irritation near the surface, but neither produces enough sustained odor underground to discourage a groundhog that has invested serious energy in digging its burrow.
Used cat litter is another popular suggestion, based on the theory that the scent of a predator’s urine will frighten the groundhog. There is some biological basis for this idea. Research on woodchuck responses to predator urine has shown that woodchucks do respond aversively to predator urine, though researchers were unable to isolate specific chemical fractions of bobcat urine that produced the same level of aversion as the undiluted urine itself.1USDA National Wildlife Research Center. Repellency of Predator Urine to Woodchucks and Meadow Voles The takeaway is that while predator scent can make a groundhog uneasy, domestic cat urine in used litter is considerably weaker than concentrated bobcat urine, and it degrades quickly in the elements. You might see temporary avoidance of a particular hole, but it is unlikely to drive an established groundhog off your property.
Castor Oil-Based Repellents
Castor oil granules and liquid concentrates are sold as mole and groundhog repellents at most garden centers. The product is typically spread on the lawn or mixed with water and sprayed over the area around the burrow. The idea is that castor oil coats the soil and makes the groundhog’s food sources taste unpleasant, and the odor underground becomes disagreeable. Some homeowners pour the liquid directly into the burrow entrance.
Results with castor oil are mixed. It tends to work better against moles, whose diet is almost entirely underground grubs and earthworms that absorb the oil-coated soil. Groundhogs, on the other hand, are herbivores that spend a lot of their feeding time above ground eating garden vegetables, clover, and grass. Making the soil around their burrow smell bad does not do much about the tomato plants 30 feet away. If your groundhog problem is primarily about garden damage rather than structural concerns from the burrow itself, castor oil applied to the burrow is targeting the wrong part of the animal’s routine.
Why Filling the Hole Is Not Enough
Some people skip repellents entirely and just fill the burrow with soil, gravel, or concrete. If the groundhog is still living there, it will dig out within a day or two. Groundhogs are powerful excavators capable of moving several hundred pounds of dirt to build a burrow, so a few shovelfuls of backfill are not much of a deterrent. Gravel slows them down slightly, but they can work around it. Concrete poured into a burrow entrance hardens into a plug at the surface, but the tunnel system continues deeper and in other directions.
Filling the burrow only makes sense after you are confident the groundhog is gone, either because it has been trapped and relocated, killed by fumigation, or driven out by sustained harassment over several weeks. Even then, you should fill the entire tunnel system as thoroughly as possible. An empty burrow is valuable real estate for the next groundhog passing through. Leaving an accessible tunnel underground is an invitation for recolonization, sometimes within weeks.2IntechOpen. Avoid Sharing of Strawberries with Birds, Rodents and Other Vertebrate Pests – Section: 2.2.9 Marmots
Habitat Modification Around the Burrow
Whatever you put inside the hole, you are only dealing with one part of the problem. Groundhogs choose where to dig based on nearby food, cover, and soil conditions. If your yard provides excellent habitat, removing one animal just opens the territory for another. Reducing cover is one of the most effective long-term strategies. Keep grass mowed short, clear brush piles, remove stacked firewood near the burrow area, and trim back overgrown vegetation along fences and foundations. Groundhogs prefer to forage near cover so they can dash to safety, so an open, short-mowed lawn is less attractive to them.2IntechOpen. Avoid Sharing of Strawberries with Birds, Rodents and Other Vertebrate Pests – Section: 2.2.9 Marmots
If your primary concern is garden damage, fencing is often more effective than any burrow treatment. A fence made of heavy-gauge wire mesh, at least three feet tall with an additional foot bent outward at the top, can exclude groundhogs that are decent climbers. Burying the bottom edge about six inches underground helps prevent digging under.2IntechOpen. Avoid Sharing of Strawberries with Birds, Rodents and Other Vertebrate Pests – Section: 2.2.9 Marmots This does not get rid of the groundhog, but it protects the thing you actually care about while you deal with the burrow separately.
Trapping as an Alternative
When burrow treatments have failed or the burrow is in a location where fumigation is unsafe (under a porch, next to a foundation), live trapping is usually the next step. A large cage trap baited with cantaloupe, broccoli, or apple placed near the burrow entrance works well. Groundhogs are not especially trap-shy compared to some other wildlife, and most homeowners can catch one within a few days if the trap is set correctly.
The catch with live trapping, quite literally, is what you do next. Relocation laws vary widely. In many states, it is illegal to relocate a trapped groundhog, meaning you are required to euthanize it or release it on site. Some states require a wildlife removal permit even for live trapping on your own property. Before you buy a trap, check your state wildlife agency’s regulations. Getting this wrong can result in fines, and releasing a groundhog in an unfamiliar area often just creates a problem for someone else while the animal struggles to establish a new burrow before it starves or is killed by predators.
Lethal body-grip traps (Conibear-style) set at the burrow entrance are extremely effective when used correctly, but they are dangerous to pets, children, and non-target wildlife. They are not a casual DIY option for most suburban properties. If you are leaning toward lethal control and the fumigant route is not viable, hiring a licensed wildlife control operator is safer and, in many jurisdictions, legally required.
Timing Your Efforts
Groundhogs hibernate, which creates a natural calendar for control efforts. They typically emerge in late February or March, depending on your region, and are most active from spring through early fall before entering hibernation again in October or November. Attempting to treat a burrow in winter is mostly pointless because the animal is deep underground in a sealed hibernation chamber, and any surface-level repellent or fumigant will not reach it.
Spring, right after emergence, is the best window for most control methods. Groundhogs are hungry and active, making them more likely to encounter traps. They have not yet produced a litter, so you are dealing with one animal rather than a family. By late spring, females may have four to six young in the burrow, which complicates fumigation and trapping alike. If you miss the early spring window, late summer after the young have dispersed is your next-best opportunity.
When Professional Removal Makes Sense
For a single groundhog in an open yard with no structures nearby, a homeowner armed with fumigant cartridges and some patience can usually resolve the problem. But several situations call for a professional. Burrows running under foundations, patios, or retaining walls can undermine structural integrity, and fumigating near a building is a fire risk. Properties with multiple active burrows suggest a larger population that is unlikely to respond to piecemeal treatment. And if you have tried fumigants and repellents without success, the burrow system may be more extensive than surface evidence suggests, sometimes extending under driveways or connecting with neighboring tunnel networks.
Licensed wildlife control operators have access to tools and methods that homeowners typically do not, including professional-grade fumigants, CO2 injection systems, and camera scopes that map the tunnel layout before treatment. They also know the local regulations, which saves you from accidentally violating wildlife laws that vary not just by state but sometimes by county. The cost for a single groundhog removal usually runs between $150 and $400, depending on your region and the complexity of the burrow. Compared to the price of repairing a cracked foundation or collapsed retaining wall, that is a reasonable investment for burrows in high-risk locations.
Other Animals Using Groundhog Burrows
One thing many homeowners do not consider before treating a groundhog hole is that these burrows frequently house other animals as well. Rabbits, skunks, opossums, foxes, and even snakes use abandoned or active groundhog burrows as shelter. Before fumigating, check for signs of other wildlife around the entrance. Fresh tracks in mud, different sizes of droppings, or fur caught on burrow edges can indicate a secondary occupant. Killing a non-target animal like a skunk inside a burrow creates a different and extremely unpleasant problem, both the smell and the difficulty of retrieving the carcass from underground.
This shared-burrow dynamic also means that if you successfully evict or kill a groundhog and leave the tunnel system open, you may inherit a different tenant. Skunks in particular are quick to move into vacated groundhog burrows, and they are generally a bigger nuisance than the groundhog was. Thoroughly collapsing and filling a burrow after the groundhog is gone is not just about preventing another groundhog from moving in. It is about closing down a piece of underground infrastructure that attracts all kinds of wildlife you would rather not have under your porch.