The Best Ways To Kill Crabgrass Post-Emergent

Best Way To Kill Crabgrass From A Lawn

Chances are, even if you applied pre-emergent to your lawn in early spring, some crabgrass still managed to germinate. Don’t fret, though. There are post-emergent techniques available to help eradicate the pesky crabgrass that did sprout.

Applying Selective Herbicides

For large amounts of crabgrass in your lawn, the most efficient way to kill it is to mix a selective, post-emergent herbicide with a surfactant and spray the patches where crabgrass is rampant.

  • For Bermudagrass, Zoysia grass, and Fescue, apply a selective post-emergent crabgrass killer containing quinclorac.
  • For buffalograss, Kentucky bluegrass, and perennial ryegrass, you can either use a product containing quinclorac or Mesotrione or both.
  • For St. Augustine grass and Centipedegrass, use Celsius, an herbicide explicitly labeled for these two turfs.

Here is a straight quinclorac product for tank mixing, here is a hose end version that is pre-mixed with a few other herbicides.

Instructions – Get Rid Of Crabgrass In One Try
If you want to supercharge the effectiveness, give the crabgrass a good watering a couple days prior and apply water soluble fertilizer to act as an adjuvant (something to make the herbicides work better).

I don’t recommend organic fertilizers for this purpose and luckily there are lots of options on the market like this hose-end Urea that are super easy to use even if you don’t have any equipment at home.

Allow the grass to grow unmowed for at least two days then apply the herbicides mixed with a Non-Ionic Surfactant to improve leaf coverage and maximum herbicidal uptake by the plants.

Time this whole sequence around a dip in summertime temperatures into the 80’s or lower if possible and then let the grass go unmowed for at least a couple more days after application.

For deeper pockets adding Pylex into the mixture (if your grass type allows) can greatly increase the kill rate. I would only recommend this extra product if doing only a single application was extremely important for whatever reason.

Spot-treating with glyphosate

If you only have a little bit of crabgrass, spot-treating with glyphosate using a technique known as sponging may be the most effective method of getting rid of it. With sponging, the glyphosate travels down the crabgrass, killing the root.

  1. Let the crabgrass grow taller than the lawn by mowing around it for a couple of weeks.
  2. Carefully mix glyphosate in a bucket with a surfactant.
  3. Dip a sponge in the mixture and wipe the top two to three inches of the blades of grass.
  4. Repeat the sponging process every four to five days over two weeks to kill the entire weed.

For glyphosate I don’t usually use Roundup, I usually use Killzall glyphosate which tends to be a bit cheaper so long as you are fine mixing it in a tank yourself.

Using baking soda to kill crabgrass

Baking soda acts as a desiccant due to its high sodium levels and damages almost any plant leaves it touches. The preferred method for killing weeds is to use the powder directly versus diluting it into a solution.

  1. Spray water on the crabgrass in your lawn.
  2. Sprinkle baking soda on the wet crabgrass blades until the weed is completely covered.
  3. Repeat after a few days, rewetting the weeds and sprinkling more sodium bicarbonate if needed.

Using vinegar as an herbicide

Vinegar is often used as an organic weed killer, especially when mixed with soap and salt. The soap breaks down the cuticle so the vinegar and salt can get inside the leaves. Once inside, they act as a desiccant by breaking down cell membranes, which pulls water out of the foliage to kill plants.

  1. Combine one gallon of 20% white vinegar, one cup of salt (table salt or Epsom salt), and one tablespoon of liquid dish soap in a bucket.
  2. Stir the solution with a plastic spatula or clean dowel to mix the ingredients well.
  3. Carefully pour this solution on the crabgrass, trying to keep it off of the turf blades.
  4. Continue to apply the vinegar solution every few days until the entire weed is killed.

Don’t Forget About Manual Removal + Hand Pulling

Really small patches of crabgrass can easily be removed by hand with just a little bit of labor.

Because the plant has a tufted root system and no rhizomes you can easily pull it out of the ground. For those that don’t want to dig I recommend using a ProPlugger to pull a plug of turf out over the weed. You can then crunch the soil back into the hole, pick up any loose stolons on the ground, and discard the plant in the trash all from an upright position and in well less than a minute per plant.

Here’s a video I made about the ProPlugger if you haven’t seen it in action before.