How to kill annual grassy weeds

June 19, 2015

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, to look out for.

How to kill annual grassy weeds

Start early, if you can

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 a 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.

  • To spot-kill the weeds, apply a nonselective herbicide. Nonselective herbicides kill plants and weeds alike, so it has to be applied to the individual weeds by hand.
  • Wearing cloth gloves over plastic gloves, wipe the herbicide directly onto the weed.
  • Don't worry about covering every single blade. As long as you get most of them, the herbicide will absorb into the weed.
  • It'll take seven to ten days before the weed starts to die. If it's not dead after two weeks, wipe on a second treatment.

If you're late getting to it

The best way to handle a few scattered annual grassy weeds is to spot-kill them with a postemergence herbicide that's formulated for grassy weeds.

  • Look for Grass Weed Killer or Crabgrass Killer on the label.
  • Mix the concentrated herbicide with water (per manufacturer's directions), then pour the mixture into a handheld sprayer.
  • Spray the individual patches of weeds.
  • To ensure that there's plenty of plant material to absorb the weed killer, don't mow the weeds just before applying the herbicide or for three days after.
  • If you don't kill annual grassy weeds now, you can expect them to seed and produce even more weeds next year.
  • Tip: Always read the herbicide's label before applying to make sure it will kill the targeted weeds and not harm your lawn.


There's only one remedy for yards taken over by grassy weeds — spray the entire lawn with a postemergence herbicide (like the ones mentioned in the "late" stage).

  • Mix the concentrate with water in a pump sprayer.
  • Spray the yard with the herbicide in the late spring or summer.
  • Apply just enough to get the weeds slightly wet.
  • The weeds should start to die within five to seven days.
  • Spot-kill any weeds that are still growing after seven days. Re-seed if necessary.
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