What Kills Crabgrass (Best 3 Products)

Crabgrass was given its name because it grows close to the ground, and its stems sprout out from the middle of the grass clump, making it look like crab legs. Once full-grown, crabgrass only lasts for 12 months; this sounds like a good deal considering the fact that most weeds live forever. The difference is in what crabgrass can do to your lawn within that time frame. Using pesticides works, but unless you have a full understanding of crabgrass, it will just keep coming back every season. Read on for some helpful hints and tips to help you ensure crabgrass is gone forever.

What Kills Crabgrass: 3 Best Products to Kill Crabgrass

Here are three of the best crabgrass killers, they are available online or from most garden centers:

OUR FAVORITES

  • Gets rid of stubborn weeds such as Goosegrass, wild carrot, and Thistle
  • Shelf life between 5 to 8 years
  • Easy to apply and very accurate
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  • Usable with the majority of herbicide sprays
  • Easy to see where the mixture has been sprayed
  • Ensures weeds are dead within 24 hours
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  • Visible results within 24 hours
  • No more weeds for up to 12 months
  • Product absorbs through the leaves to the root
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1. Southern Ag Surfactant For Herbicides – Top Pick

Top Pick
Southern Ag Surfactant for Herbicides

Our top pick, Southern Ag Surfactant for Herbicides helps to increase the coverage and effectiveness of almost any herbicide.

When it comes to herbicides, one of the main problems that users have is that their chosen product doesn’t stick to the leaves, which makes it ineffective. You won’t have this problem with Southern Ag Surfactant, as it has been strategically designed to ensure the product sticks to the weeds long enough to do the job properly.

For most herbicides all you need to use is one teaspoon per gallon of spray. For Round-up and MSMA herbicides though, you’ll need to use one tablespoon per gallon.

No more sliding with Southern Ag, your weeds will be dead and gone in no time at all.

Size: 16 ounces

Style: Combine with another product

Pros:

  • Usable with the majority of herbicide sprays
  • Ensures the surfactant sticks and doesn’t slide off the weeds
  • Easy to see where the mixture has been sprayed
  • Makes the herbicide soapy, which increases the effectiveness
  • Ensures weeds are dead within 24 hours

Cons:

  • Product can be difficult to use

2. Tenacity Turf Herbicide – Runner Up

Proactive Weed Elimination
Tenacity Turf Herbicide - 8 ounces

Our Proactive Weed Elimination product presents pre and post-emergence herbicide for residual control of weeds in turfgrasses.

How many products have you experimented with, but still haven’t found the right product to get rid of that dreaded crabgrass? Well look no further, as this will have your garden weed-free within a couple of weeks. Gone are the days of spending hours on your hands and knees picking out these awful invaders, with a handy syringe, you can carefully isolate the infected areas of your lawn.

If you are looking for a solution that isn’t going to kill your entire lawn, Tenacity Turf Herbicide is exactly what you need. It will kill stubborn weeds such as nutsedge, bent grass and foxtail while leaving your much loved lawn untouched.

Although it’s a slow, selective, starving herbicide that doesn’t promise results within 24 hours, the process is much more thorough; once the weeds are gone, you won’t need to keep reapplying it.

Tenacity turf herbicide is a miracle product, and it’s highly recommended.

Size: 8 ounces

Application: Syringe

Pros:

  • Gets rid of stubborn weeds such as Goosegrass, wild carrot, and Thistle
  • Shelf life between 5 to 8 years
  • Easy to apply and very accurate

Cons:

  • The syringe is difficult to use
  • The product does not work instantly

3. Roundup Max Control 365 – Upgrade Pick

Upgrade Pick
Roundup Max Control 365 (Weed Killer Plus Weed Preventer)

Kills weeds to the root and prevents them for up to 12 months with an invisible barrier creation in the soil

  • Rainproof in 30 minutes
  • Visible results in just 12 hours


Not only does this product kill weeds, it even makes sure they don’t return! After the first application, an invisible barrier is created in the soil, preventing more weeds from sprouting up. The majority of herbicides only kill the stems, which is why they’re back within a couple of weeks. But Roundup Max Control attacks the root.

You can use Roundup Max Control 365 on gravel, sidewalks, and patios. After 30 minutes, it’s rainproof, and you’ll start seeing results within 12 hours. The manufacturers are so confident of the product’s effectiveness, that they offer a money back guarantee if you’re not satisfied!

Style: Ready to use

Size: 1.33 gallon

Application: Comfort wand sprayer

Pros:

  • Visible results within 24 hours
  • No more weeds for up to 12 months
  • Product absorbs through the leaves to the root
  • Will ensure your walkways, patios, and driveways are always looking good

Cons: 

  • The wand breaks easily

The Crabgrass Life Cycle

Crabgrass enjoys warm weather, and it will do everything it wants to do to your lawn within 12 months. That is its life cycle; and during this time, it produces an estimated 150,000 seeds. If you’ve ever wondered why crabgrass appears to be so relentless, it’s because when they die, they leave behind those 150,000 seeds, and they start growing again in the summer. Even if the seeds don’t germinate immediately, they can last for years and will potentially spring up at any time in the distant future.

The assumption is that once crabgrass appears, you can cut the grass low and it will stop them. Unfortunately, this is not the case, the seeds will keep growing; not only is crabgrass low-growing, but even when cut down to ½ an inch tall the seed can still set. This is too low to maintain a healthy lawn; therefore, the best way to control crabgrass is to prevent the seeds from growing in the first place.

How to Prevent Crabgrass

As mentioned, crabgrass produces 150,000 seeds per year, which are all just waiting to sprout in your lawn. The only way to combat this problem is to prevent the seeds from germinating. There are several ways to do this and prevent crabgrass from growing, so keep reading to learn about some of them:

How to Prevent Crabgrass

Prevention Products: Products that prevent crabgrass growth contain pre-emergent herbicides that target germinating seeds before they start growing. Pre-emergents put a stop to seed germination and root development to prevent them from becoming plants. The problem with some crabgrass preventers is that while they target weed seeds, they can also prevent lawn seeds from growing, which will ultimately damage your grass. Before purchasing a prevention product, read the ingredients carefully, making sure it contains either pendimethalin, prodiamine, or dithiopyr. These active ingredients are sold under a range of brand names.

Timing is essential when it comes to applying crabtree preventers, this is because they are only effective before the seeds have sprouted. Applying the preventer after the seed has germinated is a pointless endeavour. Many negative reviews about prevention products have been written because the user applied the product at the wrong time.

Crabgrass seeds need the right temperature to germinate, and this is usually between early spring and late summer. During the spring months, when the soil temperature is 55 degrees F or greater for four to five consecutive days, the seeds will start germinating. You can purchase an affordable soil thermometer from a garden center to check for sure. A thermometer will help you keep track of the soils temperature so that you can time the use of the preventer properly. If you live in a Northern climate, you don’t need a thermometer though, because Yellow-blooming forsythia shrubs are in full bloom when the temperature is 55 degrees F.

After germination starts, crabgrass will keep germinating until the soil temperature is over 90 degrees F. It is also important to mention that some preventers stop working after a while during the spring season, so you’ll need to do your research to find the best option for you.

Once the area has been treated, keep an eye out so you can rectify any problems efficiently. To ensure the product absorbs fully into the soil, make sure the area is watered two days after application. If the grass starts turning brown, you probably used too much product. To correct this, dilute the chemical by soaking the area with water, this will prevent further damage. You will also need to watch for any new crabgrass sprouts, because then you’ll need to treat the area again.

Whenever you use crabgrass preventer, be sure to follow the instructions on the label about seeding. You should typically wait for a minimum of 60 days and two mowings before you overseed your lawn in the area where crabgrass preventer was used.

Frequent Mowing: Mowing your lawn at frequent intervals will keep the length of the grass consistent. All grass types have a recommended length, so you’ll need to check what yours is. Crabgrass needs a lot of light to germinate, so keeping the grass as long and as thick as you can will keep the soil surface shaded. If the lawn is cut too close, it will cause patches, making it easier for crabgrass to germinate. In general, don’t cut more than ⅓ of the grass blade at a time.

Use a Fertilizer: For best results, use a fertilizer that contains a crabtree preventer. Pay attention to the weather and apply it just before it starts raining. This will ensure it properly works its way into the soil. It will make the turf thicker and help attack any crabgrass that the herbicide missed. You will also need to make sure it’s applied at the right time. The fertilizer should be applied once the soil reaches a temperature of 52 degrees F, and within the second and third mowings of the year.

Applying the fertilizer at the right time is important because if it’s applied too early, the natural processes and the microorganisms in the soil will render the herbicide ineffective. If the fertilizer is applied too late though, then you will miss the beginning of the germination stage, which is when the herbicide works best.

Avoid fertilizers that promise ‘a quick green up’, they contain high levels of nitrogen that will drain the lawn of its nutrients, making it easier for weeds to take over later. Instead, use a fertilizer where half of its nitrogen is released slowly instead.

Mature Seed Heads: Although pulling young seed heads is advisable, it’s not a good idea to pull mature heads. You will recognize them because they resemble a fork, because they’ve got splayed seed heads, when you pull them, they’ll scatter their seeds over the hole you’ve created pulling out the mature weed. By doing this, you’ll spread around 5,000 seeds per plant! Instead of pulling mature seed heads, wait for the crabgrass to die in the fall, and then go over the area the following spring with pre-emergence granules to prevent the seeds that have been left over from sprouting.

Overseed Your Grass: Overseeding your lawn will add extra grass so that crabgrass is forced to compete with the available resources to become fully established. For the best results, overseed your lawn in the fall or at the beginning of spring to give the grass enough time to germinate and grow before the growing season for crabgrass starts. Here are some step by step instructions on how to overseed your grass:

  • Mow the lawn with a bag attached so that the grass clippings don’t go back onto the lawn and spread the crabgrass seeds.
  • Use a mechanical detacher to remove thatch, this will improve the overseeding results by allowing new grass to better connect with the soil.
  • Provide extra nutrients for your soil by applying a high-phosphorous starter fertilizer to your lawn.
  • Use a hand crank seeder to sow the grass seed, and go over the same area several times to make sure it’s properly distributed.
  • Lightly rake the lawn to help the seeds make better contact with the soil.
  • Lightly water the lawn several times a day so that the soil remains damp while the seeds germinate. Don’t oversaturate the soil by watering it too much though. Once the new grass starts to shoot, start watering the lawn less, one inch of water twice a week is enough.
  • Once the new grass is around 3 inches in height, cut the grass down to two inches.

Organic Methods to Control Crabgrass

Crabgrass thrives in conditions with high levels of potassium, magnesium, and chlorine, and low levels of phosphorus and calcium. Therefore, you can alter these conditions using chemical free methods to prevent growth. Although it will take a bit more time than store bought products, the results are the same. Here are a few suggestions.

Organic Methods to Control Crabgrass

Water Restrictions: Crabgrass needs water to survive, so by restricting its water intake, you’ll basically starve the weeds to death. You can do this by watering your lawn before crabgrass season. The mistake that many homeowners make is that they water their lawns at the end of spring, or at the beginning of summer, right when crabgrass is ready to sprout. Water the lawn about three weeks before the crabgrass growing season instead to keep the seeds from germinating.

Use Hot Water: Boil a large saucepan of water and leave it to come to a rolling boil. Add vinegar or salt to increase the strength, either one will draw water out of the plant material and kill the weeds. Carefully pour the boiling water over the affected area, making sure not to touch the surrounding plants. You will need to do this several times to ensure the crabgrass is fully dead.

Sugar: Sugar damages the soil, which restricts plant growth. Spread some sugar over the soil of the affected area, being careful not to get the sugar over other plants.

Change the Soils pH: Crabgrass grows well in acidic soils with a 4.8 pH or higher. You can prevent crabgrass growth by making the soil more alkaline by doing the following:

  • Add dolomite lime or garden lime to make the soil more alkaline and increase the pH. The amount of lime required will depend on the pH level of the soil, so your first step is to do a soil test using a home pH test kit, you can purchase one from any gardening center. To start, you will need to till or dig the bed to 8-12 inches. Squeeze the lime into a cup, spread it evenly over the soil and then rake it to 2 inches in depth.
  • Add sand, the amount you add will depend on the pH level of the soil, but you should expect to add between 3 and 8 pounds of sand.
  • Add clay, the amount you add will again depend on the pH level of the soil, but you should expect to add between 3 and 6 pounds of soil.
  • Spread a generous amount of baking soda over the area, and then water so that it soaks into the soil. Again, you can add vinegar to increase the strength.

How to Keep Your Grass Healthy

Once you’ve got rid of crabgrass, your main priority should be to keep your lawn healthy. There is no guarantee that you’ll always have a weed free lawn, but you can significantly reduce the occurrence by keeping it in good condition. Here are some tips on how to do so:

Keep Your Grass Healthy

  • Change the Cutting Height: For cool climate grasses, the cutting height should be ½ to 1 inch during the first mowing year. This will get rid of dead grass so that extra sunlight can get to the crowns of the grass plant. When the weather gets warmer during the summer months, grow the grass to 2 inches and above.
  • Mow the Top One Third Only: The top part of a blade of grass is leafy and thin. When cut, it quickly decomposes and provides your lawn with up to one third of its nitrogen requirements. During the decomposing process, the clippings help slow down evaporation and prevent weeds from germinating. But underneath the one-third is stemmy and tough, it decomposes slowly and adds to the thatch. If the thatch becomes too thick it prevents nutrients, water, air, and sunlight from getting to the soil. Additionally, when more than one third of the grass is cut, the stems become exposed through shock to the grassroots. As a result, the grass burns in direct sunlight. This means that if the ideal grass height for you is two inches, cut it once it gets to three inches. Since grass growth rates are unpredictable, having a set schedule isn’t always going to tell you the best time to run the lawnmower over it. You may need to mow it more or less, depending on the condition of the grass. You should avoid mowing the grass during the day when it’s hot, and you should also avoid mowing when the grass is too dry.
  • Aeration: Give your grass some breathing space with grass aeration. Grass roots need more than just nutrients and water, they also need oxygen. The process of aerating gets rid of small plugs of soil and this provides your lawn with some fantastic benefits. When soil gets the right amount of air, it allows fertilizer and water to go deeper into the soil with less effort. Aeration limits soil compaction so that there’s enough space for the roots to grow. It also helps to break down thatch; timing is important when it comes to aeration, the best time to do so is during the fall months because there are less weed seeds and the kids have finished running through the grass. It’s also best to aerate first to protect the open holes from the weeds, and then use a weed killer.
  • Keep the Blade Sharp and Balanced: What you don’t want is to rip out the grass. A blunt blade will cut your grass, but the cut won’t be smooth because it will tear the grass instead of cutting it. A sharp blade will ensure a clean, smooth cut with no snags, and prevent damage. Damaged grass turns into an unsightly yellow color, gets easily infected, and needs more water. An unbalanced blade will make the problem worse, and damage the bearings on your lawn mower in addition. You can maintain your lawn mower blades by sharpening and balancing them three times a year.
  • Deep Watering: Instead of giving your lawn a lot of light sprinklings, deep water it. Light sprinkling does a good surface job by providing moisture to the surface of the soil and the blades of the grass. This makes the grass more thirsty though, and encourages shallow root growth. The average lawn needs one to two inches of water per week, three to four times per week. However, this will also depend on the temperature and soil condition.

Your lawn needs water when it wilts and the dull green bottoms have been exposed. Grass will also need water when it loses its resiliency or bounce. A general rule of thumb is to water the soil until the moisture runs four to five inches deep. When the top one to two inches become dry, water the grass again. Additionally, water the grass first thing in the morning. During this time, there is less evaporation and the water pressure is high, giving the lawn plenty of time to dry out before nighttime. Lawns that stay wet during the night will attract mold, fungi, and disease.


FAQ

Here are the answers to some of the most common questions on what kills crabgrass:

What will kill crabgrass but not grass?

You will need to use a crabgrass killer of the post-emergent kind that contains Quinclorac.

What kills crabgrass fast?

The most effective product to kill crabgrass fast is a pre-emergence herbicide.

What is the best product to kill crabgrass?

There are several products you can use, such as Tenacity Turf Herbicide and Roundup Max Control 365.

Should you pull crabgrass?

Pulling crabgrass can be as effective as spraying it, but it will take a while.

Final Thought

Getting rid of crabgrass is a relatively straightforward process. The instructions and product recommendations above will help get your garden in immaculate condition relatively quickly. But remember, you can’t put your feet up and relax after the weeds have gone, you’ll need to take extra care of your lawn area to make sure that crabgrass doesn’t come back and that your lawn remains in a healthy condition.

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