When to Put Down Crabgrass Preventer (Best Preventers 2022)

In the United States and Canada, May 1 is when crabgrass preventer is typically applied to grass. However, the right timing depends on several factors, such as temperature, and location. People who live in the North will need to apply their crabgrass preventer later than those who live in the South, for example. Nevertheless, there is plenty of information you need to take into consideration, so those points will now be addressed here.

When to Put Down Crabgrass Preventer: 3 Best Crabgrass Preventers

Here are three of the best crabgrass preventers for your lawn. You can purchase these online or at your local garden center.


  • Prevents the growth of broadleaf weeds such as Poa annua and chickweed.
  • App provides step by step instructions so you can’t go wrong.
  • A little goes a long way, you don’t need much for it to work.
  • Controls a variety of weeds
  • Elements are not affected after application
  • Prevents weed growth throughout the entire season
  • Guaranteed protection for 6 months
  • Easy and simple application
  • Product is not seasonal, you can apply it anytime during the year

1. Scotts Weedex – Top Pick

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There are a lot of crabgrass prevention products that promise the world and don’t deliver. Scotts Weedex is not one of them, after one application, your lawn will be fully protected, and you won’t need to worry about a crabgrass infestation for the entire season. One bag will treat up to 5,000 square feet, making it exceptionally long lasting. Scotts Weedex can be used on any grass type except for bentgrass and dichondra. The product is very easy to use, the MyLawn app will give you the exact figures for your lawn so you can use the appropriate amount.

The product is safe for pets and children, but you will need to keep them away from the lawn for about 24 hours after application.

Size: 10.34 pounds

Style: Ready to use


  • Controls a variety of weeds including oxalis, corn speedwell, poa annua, chickweed, goosegrass, fall panicum, barnygrass, spurge, and foxtail.
  • Elements are not affected after application, product performance is effective regardless of weather conditions.
  • Prevents weed growth throughout the entire season


  • Instructions can be difficult to understand

2. Scotts Turf Builder – Runner Up

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This crabgrass preventer also contains food for your grass, making it even more effective. After the winter months your grass can lose its color, but this feed will quickly have it looking green and healthy once again. The product effectively stops crabgrass before it starts to germinate. Regardless of the weather conditions after application, it won’t have a negative effect on the product’s performance.

Your lawn will have all the nutrients it needs to thrive, as well as full protection against stifling and restrictive weeds.


  • Prevents the growth of broadleaf weeds such as Poa annua and chickweed.
  • App provides step by step instructions so you can’t go wrong.
  • A little goes a long way, you don’t need much for it to work.


  • Even though it makes the grass greener, it doesn’t get rid of all the weeds.

Size: 10 lbs

Style: Ready to use

3. Preen Extended Control Weed Preventer – Extended Control Preventer

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There aren’t many weed preventer products that actually offer a 6 month guarantee of a weed free garden, but this one does. With its flip top applicator cap, this preventer is easy to use, just pour, water, and go. It’s important to mention that Preen does not kill existing weeds, its job is to prevent them from growing. So if you’ve already got weeds, you’ll need to remove them first before application.

After the product has been applied and you’ve watered the lawn, an invisible barrier is formed that blocks the weeds underneath the surface from sprouting. Preen can be used on more than 600 established plants including ivy, daylilies, snapdragons, azaleas, common boxwoods and more. It’s best to apply the product during the spring, after mulch has been spreaded.

It’s also important to note that Preen only blocks the growth of certain weeds though, such as crabgrass, foxtail, henbit, purslane, chickweed, and dandelion. All the weeds are listed on the label, you’ll need to check if you know you’ve got other weeds growing in your garden. Other than regular lawn maintenance, once Preen has been applied, you won’t need to do anything else to protect your garden against weeds for a full six months.

Size: 4.93 lbs

Style: Ready to use


  • Guaranteed protection for 6 months
  • Easy and simple application
  • Product is not seasonal, you can apply it anytime during the year


  • The instructions can be difficult to read

When to Apply a Crabgrass Preventer

When it comes to applying a crabgrass preventer, timing is very important. Here are some tips on the best time to apply crabgrass preventer:

Apply Crabgrass Preventer

Read the Label: This might sound really obvious, but you’ll be surprised at how many people don’t read the label, especially if they’ve used a crabgrass preventer before. However, each product is different, and even if you’re using the same brand, things can change, so read the label each time and follow the instructions that have been set out by the manufacturer.

Apply Early Spring: During the summer and fall months, crabgrass drops their seeds. They stay in the soil throughout the winter, and when the weather starts getting warmer, these seeds begin to germinate. To prevent this, you will need to use a pre-emergent at the beginning of spring. The best time is between the end of March and the beginning of April. Early May is also okay, but the earlier the better. You can provide protection for your grass throughout the season by applying the protector between the third or fourth mowing.

Temperature Soil: The sun starts coming out in spring, a lot of plants start germinating around this time because the soil gets warm and stimulates the enzymes required for seed germination. Once the soil temperature gets to around 55 to 60 degrees F, the seeds will start germinating. This is generally from late spring until mid summer. Several factors such as shade, wind, and the overall climate of the area can affect the soil temperature as well. So that you don’t miss it, it’s advised that you start monitoring the soil temperature from the first week of March on.

Apply Before the Rain: The best time to apply preventer is before it rains, because the rain will wash it into the soil. Nevertheless, if you happen to apply it after the rain, water the soil straight away to ensure the pre-emergent properly soaks into the soil. The best way to determine whether it’s going to rain is to keep an eye out on your local weather forecast. If rainfall is expected within a few hours, start applying the preventer to your lawn.

Summer Pop Ups: In general crabgrass preventer lasts for two to four months after its been applied. After this time, any new seeds that have found their way into your lawn can still germinate. You should not apply it more than twice a year. Additionally, there should be a two month waiting period between each application. You can treat the areas most likely to have problems with crabgrass instead of the whole area. This may include spaces near your sidewalk and driveway. Because of the concrete, these areas absorb more heat, and crabgrass is attracted to high temperatures.

Why Use a Crabgrass Preventer

Apart from the obvious, there are several reasons why you should use a crabgrass preventer, here are some of them:

Crabgrass Competes For Nutrients: Grass needs nutrients to grow properly and become healthy and strong. One of the main problems with weeds is that they also need food, so they will steal sunlight, water, and nutrients away from grass. This causes a loss of phosphorus, nitrogen, and potassium, leaving the grass vulnerable to disease and insect infestation. Since the majority of weeds grow so quickly, they can absorb a lot of one type of nutrient, and this creates an imbalance. The grass gets overwhelmed, and this is where the damage starts.

They Take up Space: If weeds are not kept under control, they will take over an area and you’ll basically end up with more weeds in your garden than grass.

They Are Parasites: Another reason why crabgrass was given its name is because they latch on to stems and roots and refuse to let go until they’ve drained them of all their nutrients.

How to Maintain a Healthy Lawn

Crabgrass preventers are all well and good, they will do their job and rid your garden of crabgrass, but the most effective way to ensure your lawn doesn’t become overrun with crabgrass is to keep it in good condition. Here are some tips on how to maintain a healthy lawn:

Maintain a Healthy Lawn

Regular Mowing: Mow your lawn a minimum of once a week during the summer months, and once every fortnight during the spring, autumn, and the beginning of winter. The roots spread when grass is cut often, and this will help close gaps and block the weeds out.

During the summer, your lawn should be between 5 to 10 cm in length. This will prevent the grass from turning brown when the weather gets dry. Additionally, keep the blades on your lawn mower sharp, and the mower well maintained. Different mowers provide different benefits so make sure you do some research if you need to purchase one.

Regular Watering: Young lawns need frequent watering, but don’t water it too much or the roots will become shallow and they won’t establish properly. Whenever you can, use grey water from your washing up bowl or bath, or use rain water from a water butt. Sprinklers are a great way of keeping lawns hydrated, the only problem with sprinklers is that they use water from the mains, and when there’s a hosepipe ban, you won’t be able to use your sprinklers. When an established lawn goes brown, there’s no need to panic, it’s still alive; once the rain comes it will turn green again.

Compacted Grass: Grass doesn’t grow well when it’s compacted, this can cause bald spots during the summer months, and mud baths in colder weather. When soil becomes compacted, you can relieve it by sticking a garden fork into the soil 10 cm deep. When the fork gets to 10 cm, gently rock back and forwards on the handle. The prongs will open the soil up so that the roots can breathe and the grass can keep growing.

Use a Lawn Feeder: To keep your lawn healthy, it will need regular feeding. You can do this quicker and more accurately using a wheeled lawn feeder. When it’s about to rain, apply a fertilizer, the rain will help it penetrate the roots and prevent the leaf blades from burning. If there’s no rainfall, water the grass as usual. Within one week of using ferti;izer, your grass will start looking greener. In general, you should feed your grass in the spring, and again during the midsummer months.

Fill Out Bare Patches: Bare patches on the lawn look unsightly, and when left, they can spread and damage the rest of your grass. You can fill out the bare patches by cutting out a rectangle or square around the area, dig the soil up to the same depth as the turf strip, and lay it over the patch. Press it down to fill in the gaps and even out the lawn.

lawn care and preventer seed

Final Thought

The most effective way to prevent crabgrass from attacking your lawn is to make sure your grass remains thick and healthy all year round. If crabgrass keeps finding its way into your lawn, you might need to reevaluate the way you take care of your lawn. Even if you’ve used a crabgrass prevention product before, remember to read the label again and follow all the guidelines as instructed.


Here are answers to some of the most common questions about crabgrass preventer.

When to put down crabgrass preventer?

Apply crabgrass preventer when the soil temperature has been just over 55 degrees F for three days.

When should I treat my lawn for crabgrass?

It should be applied before the crabgrass starts developing, which is between early and mid spring.

Can you put down too much crabgrass preventer?

Yes, you can put down too much crabgrass preventer, and it will damage the grass.

Can you apply a pre-emergent on wet grass?

No, pre-emergent should be applied to the grass just before or a while after the rain.

How long do crabgrass pre-emergents last?

They last between two to six months.

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