Our front yard has an area approximately 10'x50' that is made up of large bolders that are covered by overgrown weeds, ivy, poison ivy and poison oak. In order to get rid of the weeds and poison oak/ivy, we feel we should kill everything on the rocks and go bare for a while. What's the best way to kill this much vegetation? Should we cover the area in thick plastic for several months to smother it? Or is a chemical solution best? Or maybe apply a chemical then cover in plastic?