Kill Broadleaf Weeds: Early Season
A broadleaf weed is any undesirable lawn plant that isn't a grass. Dandelions, plantain, ground ivy (creeping charlie) and ragweed are a few of the most common broadleaf weeds. Before broadleaf weeds start growing in the spring, apply a product called Hi-Yield Turf & Ornamental Weed & Grass Stopper Containing Dimension, which is a preemergent herbicide. It kills weeds before they sprout from seed and even kills some weeds that have just started to grow. Park your broadcast spreader over a tarp or on the driveway (grains may leak out, and a heavy dose of herbicide on the yard can kill even healthy grass). Fill the spreader and distribute the herbicide evenly over your lawn between your first and third mowings in the spring. The company says a single application will last a full 120-day season. It's available at lawn and garden centers (call first to make sure). A 35-lb. bag treats up to 15,000 sq. ft.
Kill Broadleaf Weeds: Late Season
If a few broadleaf weeds pop up in the yard (you can always count on a few dandelions), spot-kill them with a post-emergence herbicide such as Ortho's Weed-B-Gon MAX (a 32-oz. bottle of concentrate covers 16,000 sq. ft.). Look on the label for “broadleaf killer” then check to see which weeds it targets. Some broadleaf herbicides also kill crabgrass. There's no need to treat the entire lawn, just the weedy areas. Don't let them spread and create a bigger problem. Premixed herbicides are OK if you have a small lawn and only a few weeds. Otherwise, buy concentrates to mix yourself—they're a better value. Wait until the temperature is between 60 and 85 degrees F. Mix the herbicide with water (follow the directions) and pour it into a small pump sprayer. Keep the nozzle 6 to 12 in. from the weed and spray until the leaves are slightly wet.
Kill Annual Grassy Weeds: Early Season
Annual grassy weeds sprout from seed each year. The weed dies in the fall, leaving behind seeds that germinate the following spring. Crabgrass is the most notorious grassy weed, but there are others, like yellow foxtail and nutgrass. Use a preemergent herbicide to kill annual grassy weed seeds in the spring before they germinate. Crabgrass preventer is the most common, but you might as well apply an herbicide containing Dimension in the spring because it also kills broadleaf weed seeds. Crabgrass often thrives along sidewalks and driveways because the ground is warmer there, so be sure to apply herbicide in those areas.