I live in an area where ground hogs have been here as long as the early farmers were circa 1900. The den holes are under every barn, foundation of porches and decks, and even in the middle of people's yards. I knew by shape and looks that I had 3 ground hogs. A big ole fat one. A cute little one. And one that looked just normal.
I'm a engineer by schooling, so I tried everything I heard about. Here is my experience:
Gum (grape, watermelon): supposed to clog the gut of the ground hog and kill them. I tried about 10 packs of gum one year, scattered around their den entrances and around th garden. I know ants love it, couldn't tell if groundhogs ate it and whether it was effective because there wasn't a decline in the population.
Havahart trap: I learned that not just any vegetable in a live trap is a good idea because I caught the neighbors cat, squirrel, and a raccoon. Soon realized cantaloupe rinds worked best. I caught 4 of them over the course of 3 years. Noticed that ground hogs roam over a large area, eating clover, weeds, vegetables, and the like. Patience is required. And constant checking in case you do have one. Once caught, they can be feisty or calm. Just depends on how you approach and handle the trap with him inside. I drove them all 7.5 miles away (across 3 creeks, major road, and numerous wooded areas. Not sure, but we all think they returned. Not kidding. Many trapping forums say 10-15 miles is required because their dens are a complex series of tunnels which can take years to develop, also they mate and remain a social and family unit. Hence the drive to return.
Copper sulfate (causes flesh burns): supposedly putting this in their holes, which they dig through with their paws, causes severe damage to them. I used this with no proof of effectiveness. Note: copper sulfate is a root killer, so I probably shouldn't have done it but the guy who told me about it seemed knowledgeable. I wouldn't do it again.
Moth balls: dumping boxes of moth balls in every hole. I think this annoys ground hogs because 3 days later there are hundreds of moth balls thrown out into my yard. Stupid idea because they probably play with them before they kick them out of their dens.
Smoke bombs: worthless unless you can find every hole. Other forums indicate ground hogs have a guaranteed 2 entrances to a den, if they're there for more than a year, there's a network of tunnels and expansions, and hence more openings. I swear the neighbors barn (100 ft away) and garage, are all connected to my three holes. Trust me, I work out of my house and I watch my yard 5 days a week. Anyways, I bought 5 boxes of smoke bombs. That's a total of 25 smoke bombs. I've used every one of them, following directions, all holes in a simultaneous attack. Bottom line: they are expensive and useless. How do I know this? After months of bomb runs, several days later the holes are reopened, and remnants of spent smoke bomb casings thrown out of the hole.
Gopher peanuts (poison): I knew this wasn't going to work because the diet of ground hogs and gophers is different. I put one whole bottle in all 3 holes. Didn't see any dead ground hogs and didn't see a reduction in the population. A friend of mine said she put a brick form of poison in a hole and she's never had a problem since. Sounded to me like rat poison. I blew her advice off because most sites say rat poison is a waste of time because of the diet differences.
Pellet gun: I researched this for years. Borrowed a friend's gu which he said was very powerful. Stupid plastic toy it was. The issue with guns is you have to hit the ground hog in the head or it's cruel because they won't die quickly. .177 for feather friends, .22 for fur. For anything fur bigger than a squirrel, a certain muzzle energy rating is required. Okay so I bought a hunting pellet rifle with a scope, paid over $200 for the lot. Took me a while to sight in the scope, saw a ground hog about 100 ft away, shot it, hit it, he jumped and ran away. Bottom line: it's very difficult to hit a target the size of an apple at 100 feet. Even with a gun mount, these rifles take practice and precision pellets. I'll never use it again because I know I hit him and I know he ran off. Cruel, and ineffective.
Cats: rely on your or your neighbor's cat? Nah, they walk right past each other and I swear they say hello. Yeah sometimes the cats chase the ground hogs around, but seriously, a ground hog would kill a cat if it wanted. It's got the claws and strength and lives in the wild. And a cat eats out of a bowl.
Fox urine, animal deterrents: the garlic, red pepper, animal piss stuff you buy at Lowes is an waste of money. Yes it stinks. But after a few days in the sun, the ground hogs walk right past it, and sometimes eat the clover in the same spot. It's probably acting as a fertilizer haha.
Best solution: conibear trap. These are the most humane kill trap design made. Actually supported by animal rights groups. It's a spring loaded trap which comes in many sizes. Choose a #220 trap, aka 7" double-spring, which is designed for ground hogs, possums, and raccoons. Place in the den entrance, they ground hog (entering or leaving) trips the mechanism and he's dead. The traps cost 12 bucks. Get the setting tool and safety device for an additional 8 bucks. I've had mine over one hole for the past 3 weeks, and every 3 days I caught/killed a ground hog. Total: 5 ground hogs. Make sure you think through carcass disposal because you need to get rid of the dead animal some how. I bury mine ( dig the hole first before you deal with the dead animal), and keep in mind if there's one ground hog, there's another. If it is past June, they've mated and will produce one new offspring, every year. They live up to 10 years.
I've heard to fill the hole after no more ground hogs are trapped/killed because you don't want other ground hogs reoccupying the holes, or other varmints. I thought I had 3, but I've caught 5. Go figure.
So after 13 years of trying different ideas, all I know is that nothing proved itself effective other than the conibear trap, which nailed 5 of them in 3 weeks. If anyone can tell me something more effective than this, I'd love to hear it. Many ideas are urban legends, so I've found.
All-container garden, up to 40 pots now