Weed-and-feed products combine fertilizer and herbicides to do two jobs at once. But their promised labor savings can backfire if the recommended time for weed control doesn't coincide with the best time and rates for fertilizing. Most also pose an herbicide-overdose risk when used for follow-up fertilizing. Corn gluten with added organic fertilizer is the safest weed-and-feed.
Whichever herbicide you use, follow the directions. Address the causes of weeds at the same time to keep new ones from growing. And reseed the bare spots left by dead weeds. The bottom line in the war against weeds: Care for your lawn and apply only what it needs—and only when necessary.