Living on the edge

Bottom and side of my garden

I am trying something new with my garden. Every year I hate having to dig out the outline of the plot.  I was reading another blog and they talked about using cardboard to cut weeds.  What I have done is to dig out the garden dirt and then place down a layer of cardboard.  I then refill the area with the dirt, after I have taken out the weeds and rocks.  Finally, I place the ceramic tile pieces on top.  I am hoping that this will keep the weeds at bay.
Anyone have any information about this?