Grass Creeping into Phlox

My creeping phlox looks great in spring, but grass grows through it in many places. Is there a herbicide I can use to kill the grass, while protecting my phlox? Thomas Foti, Oneonta, New York

Melinda: Perennial grass weeds like quack grass can ruin the beauty of a perennial and drive a gardener to distraction.

Hand removal works well, but requires persistence, as you have probably discovered. The best time to pull weeds is after a gentle rain. But be sure to remove the roots and rhizomes; otherwise, these weeds will resprout with a vengeance.

Several applications of a total vegetation killer, such as Roundup or Finale, will control the grass. But you must apply it carefully and only on the grass leaves. If any of the chemical touches the phlox, you'll be replacing those plants.

You may also want to check out grass killers containing Fusilade (fluazifopbutyl) like Ortho's Grass-B-Gon, which is labeled for use in landscape plantings. These herbicides are formulated to kill grass weeds without harming landscape plants. Follow the label directions carefully, and use only on recommended plantings.