Crabgrass, crabgrass, crabgrass everywhere….

September 6, 2011 at 10:06 AM Leave a comment

How To Kill Crabgrass


Don’t waste any time when you have a crabgrass problem.
See Crab Grass? Kill Crabgrass! Now!
The innocent looking, attractive green seedlings quickly become voracious monsters that can devour your entire lawn.

What will it cost in terms of time, energy and money to get rid of this nuisance?

Unfortunately, this is one of the worst weeds to get rid of. How bad is your infestation? How big is your lawn area? Are other garden areas affected?

Learn what options you have before you embark on this process. Like many other pest problems, you’ll have to fight more than one battle to win this war. Take a quick look at these ideas, then get to work!

We’ll start with lawns, since this is the most common problem area. Other articles are available to assist with crabgrass prevention. Right now, it’s time to fight! First, are you certain that it’s crabgrass? If so, proceed. If not, click here to see the Crabgrass Pictures photo gallery


The Fast Way To Kill Crabgrass In Lawns

The fast way to kill crabgrass could also be a fast way to kill your lawn grass.

Many lawns will tolerate a chemical spray designed to kill crabgrass. Many different manufacturers of garden chemicals offer their own version of crabgrass killer. One common variety of chemical is MSMA, or monosodium-acid-methane-arsonate. Some companies have other versions of methane-arsonate, such as DSMA or CAMA.

Does that sound too confusing? How important is this?

It is VERY IMPORTANT to read the label on crabgrass killer.

How important? Crabgrass killer will kill some varieties of grass lawns, under any conditions. It will kill other varieties if used incorrectly. To borrow a famous phrase: It will kill some of the grass all of the time, and all of the grass some of the time!

St. Augustine lawns and centipede grass are particularly susceptible to most crabgrass killers. They are likely to suffer injury, and may be killed. Some products may permit their use on these grasses at lower concentrations, others say not at all. Bermuda, zoysia and bent grass may be fine for applications of crabgrass killer, but not at all times of the year. Fescues and ryegrass may be alright with some products, or some concentrations, but not all.

Please read the label before you buy, and read it again, before you apply!
Now that you are sufficiently paranoid, let’s proceed.

You can successfully kill crabgrass in some lawns with products designed for that purpose. This should be marked clearly on the label. They are available as concentrates that can be mixed in a tank sprayer. Use no more than the recommended amount. It is always better to do a repeat application than to use a stronger mix, thinking it will work better or faster.

Do not use these concentrates in a hose end sprayer unless it is the type that allows you to dial in the setting for the correct concentration. The liquid fertilizer sprayers do not permit this.

Products are also found in a ready-to-use bottle for spot treatments and small areas. Be careful with these versions. Some spot treatment products may not be designed for use in a lawn.

If the label says “non-selective”, it will kill anything it contacts. You want to use a “selective” killer intended to specifically kill crabgrass in a lawn.

If the crabgrass you are spraying is young, it may die after one treatment. More mature weeds may require one or two repeat applications. Follow the interval schedule on the label for the repeat time.

Don’t mow the lawn prior to applying the chemical, since you want more leaf area of the weed to soak up the spray. Don’t water after spraying for 24 hours, and if rain is forecast, it may be better to wait and apply the treatment after the storm.

Thoroughly rinse your spray equipment immediately after use. Avoid residue that could clog the unit or affect plants later. Don’t mix more product than you will use in one application. Potency can diminish if the mix sits for days before it is used.

It is not uncommon for a lawn to show discoloring after being sprayed with chemicals for killing crabgrass. This should not be a cause for concern, if you used the appropriate dosage. If you see yellowing of your lawn, just be patient, and the lawn should grow out to its normal color within one or two mowings.

One Final Caution: Hot Weather!
Trying to kill crabgrass in your lawn when the weather is extremely hot will place additional stress on your good grass. If you spray when the temperature is over 85 degrees, the lawn can incur more damage than if you spray when it is cooler. It is best to wait for a cooler spell, if possible. If that is not likely to happen, then spray very early in the morning or later in the evening, avoiding the hottest part of the day.


Using Other Weed Killers To Kill Crabgrass

Many homeowner like to use a weed and feed fertilizer. These products are designed as a convenience to help control broadleaf weeds in your lawn, while you fertilize. They will not kill crabgrass.

Broadleaf weeds and grassy weeds are completely different types of plants. Different chemicals have been designed for each group. Always use a product intended for your purpose.

If you find a granular weed and feed that specifies it will kill crabgrass, use it if you have a minor problem. Realize however, that the granules have to land and stay on the weed to be absorbed. This means many crabgrass plants could be missed. A liquid spray allows you to cover the weeds more thoroughly.

Weed killers like Round-Up that are all-purpose killers are able to kill crabgrass, but they will also kill your lawn. Use these non-selective killers only in places where you can avoid spraying them on desirable plants.

Natural or organic products may be available in your area. These are often derived from plant oils, sometimes they are salt-based products. Even vinegar, at full strength, can kill crabgrass and other weeds. Typically these will be non-selective, and will also cause damage to your lawn. (Vinegar at a normal household concentration of 5% is not strong enough to kill crabgrass with one application. Read more at Vinegar, the Weed Killer.)

Another natural method to kill crabgrass is to pour boiling water on the weed. This usually kills any weed. It also usually kills everything. A creeping grass like Bermuda or St. Augustine may recover from such a treatment, but test it on a small area first if you are inclined to try it.


A Last Resort?

crabgrass kills lawn grassWhen crabgrass has grown to the point of forming a dense mat or clump, it may have smothered your good lawn grass. If this is the case, you will have to reseed the area. In this situation, it may be acceptable to use a non-selective weed killer, since the crabgrass is a worse problem than losing a bit more grass.

If the crabgrass clumps are somewhat isolated from each other, make a spray barrier. Use an open-bottom cardboard box or roll a sheet of cardboard into a large tube. Confine your spraying within this perimeter, and spray when there is no wind. This may reduce the sideline damage to the surrounding lawn.


The Slow Way To Kill Crabgrass In Lawns

Put on a pair of gloves. Grab a serrated knife or a V-shaped weeding tool. Slice into the root of the crabgrass. Pull up the weed and discard. Repeat.

No fun? But all kidding aside, sometimes that is not a bad approach. You might be surprised what you can accomplish by taking 15 or 20 minutes each evening. Start on one side and methodically work your way across the yard. You can cover a good size area each week this way.

Enlist the help of a family member and have a nice conversation outside each evening as the air cools. Kids can be surprisingly effective at this when they are helping you, and not being ordered to do it by themselves. Just think, you get less exposure to chemical or TV pollution, while you kill crabgrass for free, plus the bonding!

As a side-note, related to the chemical element, you should be aware that MSMA is an arsenic based product, and it does leave residue in the soil. This may be a cause of concern for some individuals or situations.


Kill Crabgrass In Other Areas

Crabgrass in ornamental groundcovers and flowerbeds can be accomplished with certain selective chemicals that target all grassy weeds.

Ornamec is a very effective, selective grass killer that is safe to use around most shrubs, trees and ground covers. Check their extensive list on the label to be sure your desired plants are considered to be safe.

You may be able to kill crabgrass that is young with only one application. Older plants may take 2 or 3 shots. Ornamec is an expensive product, but worth it. A small amount of concentrate covers a large area when mixed. Be sure to mix it with the surfactant that is included, to get the best absorption of the chemical.

Another choice applies only to succulent ground covers, like ice plant. Magnesium chloride, a salt compound is effective at killing both grassy and broadleaf weeds in ice plant. It burns the weeds but the ice plant has sufficient water reserves to be protected. No water can be applied for 5 days or the weeds may recover. “Killer – Ice Plant Weeder” is one version of this, available in some areas. It is not very concentrated. The mixing ratio is only 1 to 1.



Winning The Crabgrass War

The key factors in being able to successfully kill crabgrass are worth summarizing:

  • Start early. Killing young plants is easier with less potential harm to lawns and desirable plants.
  • Kill crabgrass before it goes to seed to avoid next year’s war.
  • Stay alert. New crabgrass plants can start throughout the warm growing season.
  • Follow label directions accurately to prevent bad results.
  • Be persistent and be patient. Try to kill crabgrass at least partially during the warm season, then prevent its return.
  • Know your enemy. Read the article Getting Rid Of Crab Grass for more tips on dealing with this problem on all fronts.

This article has focused on how to kill crabgrass that is already growing. Crabgrass prevention is an important strategy for long term effectiveness. Read about this technique in the article When To Apply Crabgrass Preventer.

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Go to Crabgrass Pictures

Go to Getting Rid Of Crab Grass

Go to Crab Grass Killer for St. Augustine Grass

Go to Home Page of Lawn Care from How To Kill Crabgrass


Entry filed under: Green Information.

Now is the time for thickening up your lawn. City Council Passes Urban Agriculture Ordinance

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