ihave a small area in back garden for vegetables mainly onion sets, lettuce. This year in particular it has become infested with weeds mainly of same type. they are so numerous impossible to weed out. on my return from hols recently the onion sets were completely overgrown by a blanket of weeds. i usually dig well before winter. does covering the area with plastic have the desired results or will the seeds remain in the ground and come up when i plant the sets. my wife will not allow any type of weedkiller