I forget the name of the stuff we use, but gophers were a problem with other varieties. This one is a brown plastic that is not easily chewed through with a built in emitter every 18 inches. I simply plant a plant at every hole or every other hole (depending on the size of the plant). This year I put parsley or peppers between my tomato plants and they seem to be doing much better than usual because the tomatoes help to shade them from the intense sun. The line is buried to decrease water loss. The soil immediately under the plants seems moist and rich, but I would agree, the soil in the isles is only one step away from being a sun baked brick! Guess that also helps deter the weeds
