When to Apply a Pre-Emergent Crabgrass Preventer [ Before or After Rain & Wet Grass?]

Most annual weeds such as crabgrass start to grow in the spring. During this season, the temperature of your lawn’s soil begins to warm up and provide a very good environment for germination.

The best time to apply crabgrass pre-emergent is early spring when soil temperature rises to about 55 °F. Put down the herbicide just before it is forecasted to rain but not on wet grass. Rain will wash the pre-emergent into the soil and stop crabgrass seeds from germinating.

Some pre-emergents such as are not very effective and can allow a few seeds to germinate even with the perfect timing of the season, month, and soil temperature. Some of the best crabgrass pre-emergents I’ve found to be very effective include:

1. Snapshot Granular
2. Syngenta Tenacity Turf Herbicide
3. Dimension 2EW
4. Barricade 65 WDG Pre-Emergent Herbicide

Keep in mind the timing for application may differ depending on the climatic zone or region you fall in. The tips I’ve illustrated below will help you get it spot-on.

When to apply crabgrass preventer

Three things will help you know it is the right time to apply a crabgrass preemergent herbicide:

  • Season – early spring
  • Soil temperature rising to about 55 °F
  • When the weather forecast shows it’s about to rain.

Here’s a quick infographic with the guide. I’ve explained in detail below the graphic.

When to apply crabgrass preemergent - before or after rain and when grass is wet

Crabgrass is an annual weed. As such, it spreads by seed and not through rhizomes. You want to control crabgrass by preventing its germination with a pre-emergent, otherwise, killing full-grown weeds can be very difficult.

Timing Tips to Put Down Crabgrass Pre-emergent

There are various methods you can use to know the right time to put down pre-emergent in your lawn. While most people choose to use a weather map, the method can be erratic because the forecast is usually for the larger region and not your specific area.

The timing should, therefore, be on point, but how do you know when to apply crabgrass preventer? Here are a few pointers to help you with the timing:

Early Spring Season

Crabgrass germinates from seeds that dropped in summer or fall. These seeds stay in the soil through winter and start germinating when the weather starts to get warm – usually during spring.

To prevent crabgrass from germinating in your lawn, apply a pre-emergent early spring because this is the time when the weed will start to sprout in your lawn.

Any time between late March and early April are the perfect times to put down a preemergent herbicide such as Snapshot to give you protection all season long.

Snapshot 2.5 TG Granular Pre-Emergent Herbicide
170 Reviews
Snapshot 2.5 TG Granular Pre-Emergent Herbicide
  • Snapshot 2.5 boasts more control than any other pre-emergent herbicide on the market
  • Up to 6-8 months of control for 111 broadleaf and grassy weeds
  • Application rate: 2.3 to 4.6 lb per 1000 square feet

If you’re late, you can still do this in early May.

Apply in early spring to prevent the germination of crabgrass, chickweed, poa annua, and other common lawn weeds before they start to spread. Apply before the 3rd or 4th mowing to protect all season long. Scott’s Turf Builder Halts Crabgrass (label).” – Scotts

Warm Soil Temperature

Spring is when the sun starts to come out. This is when a lot of plants germinate because the heat from the sun warms-up the soil, activating enzymes that stimulate seed germination.

Crabgrass seeds start to germinate when the soil temperature reaches about 55 °F to 60 °F, usually from late spring through to mid-summer.

Soil temperature may sometimes be affected by other factors such as wind, shade in your lawn, and the general climate of where you live. So be sure to take soil temperatures on a daily basis as soon as March starts.

The best time to put down your pre-emergent is when the soil temperature is around 55°F to inhibit the root development of the germinating crabgrass seeds. This will go a long way in helping you control this tenacious grass weed for the whole season ahead.

Before or After Rain?

The best time to apply crabgrass preventer is before the rain. After it rains, the preventer will have been washed into the soil and crabgrass seeds to stop them from developing roots and germinating. If you apply after rain, water your lawn immediately after to wash the pre-emergent into the soil.

When the rain comes, it will wash the herbicide into the soil and the crabgrass seed killing it before germination.

You should be careful not to apply crabgrass preemergent herbicide too early because it will break down and become less effective.

Most good crabgrass pre-emergent products indicate that it is a good practice to water the lawn a few days after application in order to wash off the concentrate into the soil.

Pro tip: Follow your local weather forecast closely. As soon as the forecast shows it will rain in a few hours, start putting down a crabgrass preventer in your lawn. In case it does not rain 2 to 3 days after application, ensure that you apply water on the herbicide as per the instructions on the product’s label.

When to apply crabgrass preventer

Read Herbicide Labels

The best way to determine a good time to put down a pre-emergent herbicide for preventing weeds such as crabgrass, foxtail and goosegrass is to read the label of your preferred herbicide.

Each manufacturer recommends the best time to apply for the best result. Some products will give you season-long control of lawn weeds while others provide short-term solutions and probably spaced-out applications

Barricade can even be applied in the fall for crabgrass control the next season. Dimension can be applied as early as March 1.” – Kansas City

If you are not very experienced at caring for your turf, I would recommend that you try these long-term solutions for preventing and getting rid of unwanted weed grasses in your lawn.

Types of Pre-emergents

When to apply crabgrass preventer or preemergent

So far, we can categorize these herbicides as short and long residual preventers. Your current problem and level of experience may determine which one you should choose as a pre-emergent solution. I have a full review breakdown on different Pre-Emergent products here.

The Best Short residual pre-emergent

These usually last for about 60 days after application. Though the best time to apply may depend on the weather pattern, the actual best time to apply crabgrass preventers with short-lived effectiveness should be around Mid-April.

Examples of short residual pre-emergents on the market today include Scotts Halts, Team, and Tupersan Crabgrass Control. I personally like the Scotts Halts product listed below…

Scotts Halts Crabgrass & Grassy Weed Preventer (10,000sq-ft)
30 Reviews
Scotts Halts Crabgrass & Grassy Weed Preventer (10,000sq-ft)
  • One application prevents crabgrass all season long
  • Apply in spring to prevent crabgrass and problem weeds all season long
  • Fall application prevents winter weeds, such as poa annua, henbit and chickweed

The Best Long-term residual preventers

If you have no idea how to time the application of a grass weed preventer, I would recommend you go with the long-term solutions.

A single application of these herbicides will rid your lawn of crabgrass throughout the season.

The best examples include Snapshot and Dimension. You can apply any one of these earlier than the timing of the short-term options. The effect will last throughout the season.

If you need just one suggestion to go with after doing all the research, I would highly recommend Snapshot listed below…

Snapshot 2.5 TG Granular Pre-Emergent Herbicide
170 Reviews
Snapshot 2.5 TG Granular Pre-Emergent Herbicide
  • Snapshot 2.5 boasts more control than any other pre-emergent herbicide on the market
  • Up to 6-8 months of control for 111 broadleaf and grassy weeds
  • Application rate: 2.3 to 4.6 lb per 1000 square feet


Can I use pre-emergent to kill existing weeds?

can i use a pre-emergent to kill existing weeds?

It is a rule of the thumb that most pre-emergent herbicides do not get rid of crabgrass and existing weeds. This goes for Scott’s Turf Builder Halts Crabgrass and Barricade – the most popular preventers.

However, Dimension can be used when crabgrass is still very young (about two leaves young).

When should I water after applying a pre-emergent?

When should I water after applying a pre-emergent?

If it does not rain a few days after application, it is a good practice to water your turf 2 to 3 days afterward. This will wash the herbicide off the leaves into the soil where it will prevent the germination of grass weeds.

Can you apply a pre-emergent on wet grass?

Can you apply crabgrass preventer on wet grass?

When applied on wet grass, crabgrass pre-emergent will most likely stick on the leaves. Some products such as Crabgrass Barrier recommend applying it on wet grass. However, you may need to water your lawn soon after putting down the herbicide.

The reason for this is that you really want the herbicide deep in the soil to prevent crabgrass from sprouting. So, if you apply on wet grass and then it fails to rain, ensure you water your lawn with a sprinkler to wash the herbicide into the soil.
Also, see our guide on “Is it ok to mow wet grass” so you can plan on the perfect time to put down a pre-emergent and when to cut it afterwards.

How long do crabgrass pre-emergents last?

How long do pre emergents last

Pre-emergents last 2 to 6 months, meaning they will prevent the germination of weeds in your lawn for quite a long time.

However, not all of them are the same, so be careful not to apply a pre-emergent that might deter your grass seeds from growing.

If you already have crabgrass germinating in your lawn, use a recommended crabgrass killer such as Tenacity to destroy the grassy weed.

How often can you apply a crabgrass pre-emergent?

How often can you apply a pre emergent

Since most weed prevention herbicides last up to 6 months, it is highly recommended that you apply twice per year.

You should allow at least 2 to 6 months between applications, and ensure that you do not apply on newly seeded lawns. Some pre-emergents can cause slow or poor germination of some grass seed species.

If you’re late, you might want to try post-emergent weed killing options. Check out my ultimate guide on the best ways to get rid of crabgrass in your lawn here.

Crabgrass Control Before Germination

Your timing needs to be perfect for the best results. Here are tips to help you with the timing.

  • Take and track soil the temperature of your lawn. The best time to apply a crabgrass pre-emergent is just before the rain when the temperature is between 50 and 55°F.
  • You can observe dogwoods or forsythia and use them as an indicator. In this case, start the crabgrass control measures just before the dogwoods begin to bloom.


18 thoughts on “When to Apply a Pre-Emergent Crabgrass Preventer [ Before or After Rain & Wet Grass?]”

  1. Can I overseed my lawn after applying crabgrass preventer ?

    • As a general rule, wait at least 60 days and at least two mowings before overseeding lawn areas where crabgrass preventer was used.

      • Hi I will need to overseed some areas next summer so when should I apply my pre emergent

        • You can put some down now if its not below freezing on a regular basis. Waiting until after seeds germinate will harder than it has to be. Winter pre-emergent weed control treatments should be applied before the ground temperatures get above 50 degrees. Afterwards you’ll be combating the germinated seeds.

  2. It doesn’t grow thick in shady areas. It would also need plenty of soil moisture to keep it actively growing when crabgrass season has begun.

    • That’s true Renee, thanks for mentioning it. It still grows which can be a hindrance, so best to get it under control wherever you see it pop up.

  3. Crab grass preventer AND over seeding info both advise early Spring. I’m confused because I assume the crab grass preventer would kill the grass seed. HELP !!!!

    • HI Eleanor, I need to update the info and make it more clearer. As a general rule, wait at least 60 days and at least two mowings before overseeding lawn areas where crabgrass preventer was used.

  4. Can I apply crabgrass preventer Scotts Halts? I just treated my lawn with turf builder bonus.

  5. After I apply Scott’s crabgrass control when can I apply a weed and feed.

    • I would wait around 30 days for those or just do Scott’s crabgrass control and then just a straight up fertilizer without any weed prevention.

  6. When crabgrass is pulled out, will it grow back if some of the roots are torn off and left in the ground?

    • Hi Linda, yes most likely it will grow back. Crabgrass is a nasty little bugger so best to get all of it out of there and then to use pre-emergents in the spring and fall.

  7. I live in the middle AZ, and starting January 2020 and still ongoing, we set the new record for the hottest and dryest year in AZ history. We’ve had more +110° days and less rainfall (less than 1/2″) than Arizona has ever seen, and while spring 2019 was the coldest & wettest spring on record, this year, unfortunately, has virtually zero rainfall expected. I bought my property about 4 years ago, and it was beyond overrun with crabgrass. Literally every inch of my yard (bare ground made mostly of caliche clay except for my 2 pine trees) has a mature network of crabgrass roots that seem like they’re all connected to each other. I have pinched nerves in my back several times and actually developed “tennis elbow” trying to eradicate this devil of a weed as the only thing that seems to make any progress is digging up as much of the roots as I can, by hand. I thought I might have gotten the upper hand this year, finally, but I noticed new green shoots already in various areas of my yard. The ground is not yet 55°, as it gets into the upper 30s to mid 40s at night still, but if I’m already seeing fresh growth, would you recommend putting down a pre-emergent now? I saw that you mentioned the option for a type that can be applied in the winter, could that possibly be an option to use now? Our rainfall happens out of the blue usually, and in 2 years hasn’t even gotten the ground wet enough to effectively soak granules into the ground, so I’d definitely have to water my “dirt” after application. I’m not worried about “lawn safe” products, as the only thing green in my yard is grassy and broadleaf weeds, but I don’t want to use something that could kill my pine trees, as the shade they provide keeps my house about 20° cooler during summer. Any help or suggestions you might have would be greatly appreciated, I’m at my wits end and can’t keep wrecking my body for as little progress as I’ve made. =(


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