You cut holes in the plastic and put your plants in the hole. That way the weeds don't grow up around your plants. We plant clover inbetween the plastic for ground cover--then the clover dies and provides nitrogen for the soil for next year. We also plant flowers wround the border, which we can cut and use for our guest rooms. We also run soaker hose under the plastic. This way we can water primarily where the plants are and it helps to control evaporation during the summer. It works great in theory. As my advisor says, "in gardening, once every 7 years it all works out..."
As for the tractor, I still can't decide what to do. I think I'm going to rent a bigger tractor one weekend with a back hoe and loader to play around with. I want to see how it compares to the BX, and I want to see how I feel about more machine.
As you can see, I can get in enough trouble with my garden tractor alone.