@Moonhowl, I'm glad you mentioned the tar paper.
Many times tar paper can be obtained for free. People do a repair job and discard the leftovers. I have picked up 3 rolls of tar paper in the past 3 years. Cut the tar paper to fit; double layer if necessary. I place bricks or concrete blocks on top of the tar paper. This makes a good weed barrier around trees, planting beds, along fence lines (well, not if you have 90 acres of the stuff
) and if the brick/block is put down correctly, one can even use the lawnmower and skip using a weed eater.
For weeds that try to crawl under the barrier, you can use a trenching tool and place a folded piece of tar paper (or aluminum flashing) vertically to stop the weeds from spreading.
Edit to add: I am not sure if 'trenching tool' is the correct term; the flat shovel used for edging is the one I refer to. Sorry.
