Try this stuff:
http://www.critter-repellent.com/index.php
Directions for Use with Groundhogs
Shake-Away - Small Critter Powder
Groundhogs can cause significant damage to yards, landscape, gardens and flowerbeds. Their holes/burrows make a nice looking yard a mess. They also love to eat "greens" grown in gardens and flowerbeds
Scroll Down to See Instructions on How to Use Shake-Away to Rid your Groundhog Problem
Small Critter Powder
Important Note: Critters are invading your property for one or two reasons: Food and/or Shelter. If you can remove the "source" of their reason for trespassing AND provide a motivation for them to leave, you will likely be successful. Eliminate the food source by securing it or moving it, if possible. Cover or close their desired place of shelter if you can. Then use Shake-Away to communicate that the risk of the area is greater than the potential reward. The concept of using a fear based repellent is to change animals visiting and/or feeding habits by sending the message that this is no longer an easy target and that the area is home to a prowling predator and therefore is unsafe.
Coverage: Shake-Away powder covers more area than even larger-sized competitor products. Each 20 ounce bottle of Shake-Away Fox Urine Powder will cover approximately 600 linear feet when applied as directed. This equals up to 6000 square feet of protection per bottle. You will receive up to five feet of protection on each side of the powder when applied directly to the ground.
How to Apply: Sprinkle Shake-Away lightly, directly on the ground around the perimeter of the area you are trying to protect. Keep in mind as you are treating an area to rid them, you are persuading them to find new shelter, and or a new food source. Be sure to follow directions closely and give up to 2-3 weeks for results to be obtained
General Use: Apply Shake-Away powder twice a week for the first two weeks, then twice a month for maintenance. Sprinkle Shake-Away powder lightly around the perimeter of your bushes, trees, garden and flowerbeds.
Gardens-Flowerbeds: Sprinkle Shake-Away powder approximately one foot away from plants and around the perimeter of your vegetable garden. Shake-Away powder can also be sprinkled lightly over bulbs, bushes, flowers and trees for maximum coverage.
Burrowing Animals: Sprinkle Shake-Away powder directly into every hole you find in your yard, flowerbeds, along foundations, etc.
Inside and Under Buildings – Place 2 to 3 ounces (golf ball size) of Shake-Away powder on a paper plate or the like. Place one plate for at least every 10x10 area (100 sq. ft.) where small critters are getting in. Replace every four to six weeks or as needed. Be sure to “plug” the areas that the critters are entering after they leave?.
"Hard to Get To" Areas Inside and Under Buildings (Garages and Sheds): Shake-Away works great inside old sections of nylon stockings. We call these "Stocking Balls". Each 20 oz container of Shake-Away makes about 10 "stocking balls" that can be "tossed" into place. To utilize this tip:
Cut up old nylon stockings into about 6-8” sections.
Tie off one end and place a "golf ball sized" portion of powder inside the stocking.
Tie off the other end.
Toss these “stocking balls” into (under) the areas you are treating.
Place (toss) one “stocking ball” for at least every 10 x10 area (100 sp. ft.).
Replace every four to six weeks or as needed. (click to see pictures here)
Be sure to “plug" all areas that the critters are entering or exiting after they leave!
• Shake-Away’s patented formula will not harm or burn your plants, bushes or trees.
• Shake-Away is not affected or diluted by light or moderate rain, but may need to be reapplied after heavy rain.
• Shake-Away Fox Urine Powder is 100% natural, non-toxic and safe for use around children, pets, plants and the environment.