If you use enough staples, it's fine. I have only tripped once over such an installation, and it was where I had run the radials down into a depression and used an insufficient number of staples to hold the wire down into the low spot. The last time I did a wire-on-ground installation with staples, it was completely eaten by the grass runners after just a few weeks. Completely buried. OP: go to Lowe's and buy several bags worth of staples. Don't be cheap. Put one every 12" to 24" depending on the terrain, and you will be fine.