2 other things. When you click on the scene area in the tree to the right  and look upto the top right you may want to turn off your ground. This is an option. Basically they are telling you that from inside the vertex modeller you need to create what are called shader domains by selecting only the area you want with a specific map. A texture map for the whole thing is also an option. But the only way the program can treat things on an object seperately is by telling it what domains you want.

No need to think outside the box....
    Just make it invisible.