Q: I spent last year spraying the yard with a herbicide to get rid of a large crop of weeds — mostly Bermuda grass. Now that I'm ready to plant, the weeds have gotten worse in the backyard. I sprayed the whole yard equally, let the weeds die, tilled the yard under, waited for the regrowth, and repeated the actions. Why is there a massive regrowth in the back yard but not the front? And what can I do to get rid of the weeds once and for all?
—Geoff, Toledo, Ohio
A: Roger Cook replies: It may be that your back yard is sunnier than the front and promotes more growth. Or there is a greater source for the weed seeds in the back yard than the front. Identifying the weeds may also help you discover the problem. With some grasses, if they are not completely dead when you rotate, every little piece can send out new growth. If the weeds are blowing in you may be able to identify the source and eliminate them. Covering the back yard with plastic will keep the weeds from regenerating, but plastic is unsightly. Weed barrier may be a better solution. Another option is to get a covering on the ground: mulch, grass, and ground cover will all provide competition for the weeds. Also the timing of your spraying is critical. Here in New England spraying in June and July knocks down the weeds before they set seeds. The end of August and early September is the perfect time to roto-till and install a lawn.