An apron works great, just use landscape staples to secure it until time/grass covers it over. I put one in years ago aroung a 7x13 dog run that we used to use for a rabbit play area and is now used for broody hens and have never had a problem. Because it was originaly used for the rabbits the apron goes for 18" inside the enclosure as well as outside and I never had a rabbit dig out or a pred. dig in. After about 3 months the grass grew up around the outside and completly covered the apron. The inside portion took a bit longer because the bunnies ate all the grass, but was covered by dirt within 6 months.