Image is a selective post-emergent weed killer for southern lawns, aimed at the weeds that shrug off ordinary treatments: yellow and purple nutsedge, dollarweed, wild onion, sandbur, and annual bluegrass. It works slowly by starving the weed; expect discoloration in a week or two and dead weeds in three to five.

Apply after the lawn has fully greened up in spring and before fall dormancy, never during transition. Mix in a pump or hose-end sprayer and water in afterward. It is safe on most warm-season grasses; check the label, and skip St. Augustine for winter weed control.