When to Apply a Pre-Emergent Crabgrass Preventer

Pre-emergent crabgrass preventer

Crabgrass is a beast of a weed. It is hearty and hard to eliminate. Not only is it difficult to control, but just one single weed can produce thousands of seeds in its short lifespan.

Lucky for humans, crabgrass is not harmful to us, but it certainly is unpleasant to look at. Because of its deep color, it sticks out like a sore thumb. Its hearty, ugly quality makes it a lawn enthusiast’s worst enemy.

Getting rid of crabgrass is not easy, and it is not a one-and-done treatment. Before starting any type of treatment, it’s important to have the right expectations. The battle against crabgrass may take a multi-year treatment plan.

What Is Crabgrass?

The species of weed typically can be characterized by broad, flat blades. When allowed to grow to full maturity, crabgrass will grow a long flowering stem that can spread spreads across many neighboring lawns.

This hearty, light green clump of grass can be easily confused for other weeds, like fescue.

But, it can typically be distinguished by its color and size and can help to recognize it accurately. Tall fescue grass is usually darker green, fairly thick, and grows very fast.

Crabgrass is a low-profile weed, meaning it grows low to the ground. This makes it difficult to mow down. It also helps this weed hold up better to foot traffic. 

Unlike other weeds like clover or nutsedge, crabgrass is an annual weed. Meaning, that once it dies, it will not grow back.

But just one weed can spread thousands of seeds resulting in lots of future crabgrass weeds.

And those weeds can be spread across multiple lawns, so even if you are able to tackle any weeds by doing it yourself or with a professional lawn care service before they have a chance to seed, there is a strong chance that a seed (or seeds) from a neighboring lawn will find its way to yours.

Crabgrass becomes more problematic when summer approaches because these weeds thrive in hot and dry weather conditions.

Given the climate here in Texas is hot and hotter during the summer months, crabgrass really thrives in the hot, dry soil.  It is drought tolerant and is often the last green thing on the lawn. 

So how do you stop this seemingly unstoppable weed? The best way to get rid of crabgrass is to break its life cycle.

Pre-emergent is the best way to do this.

This type of herbicide prevents crabgrass seeds from germinating, stopping them before they can even develop roots and prevent them from emerging.

It’s important to remember that pre-emergent cannot eliminate a weed that has already sprouted.  This way, there is no chance of the weed spreading seeds for future weeds to sprout.

And as an added bonus, there is no weed growing in the lawn as an eyesore.

How to Prevent Crabgrass.

The timing of the application of preemergent is critical for its success. Preemergent is aimed to prevent the seeds left behind from the previous season from emerging.

It is nearly impossible to give general time frames for applications of pre-emergent. It is almost impossible to make claims like “Apply pre-emergent in February or March in order to prevent crabgrass.”

The truth is, Crabgrass does not care what month of the year it is. It only cares about the conditions.

Then consider that March in Texas and March in Idaho have extremely different conditions, and both have crabgrass. 

The best time to prevent crabgrass is when soil temperatures reach around 55 degrees Fahrenheit.

It must be applied before the crabgrass seeds begin to sprout, but late enough that the product will still be effective.

By timing its application correctly, you will stop new weeds from growing in your yard. If timed wrong, your pre-emergent will be far less effective.

It is possible to apply pre-emergent herbicides too early.

If it’s done too early, the pre-emergent will be treating soil where no weeds are sprouting, and the product will lose its effectiveness over time.

When the application is made too late, the product doesn’t have enough time to work before the seeds germinate.

Once the soil temperatures have averaged around 70 degrees Fahrenheit, most of the crabgrass seeds should have germinated.

The 411 On Soil Temperatures.

As stated earlier, the initial emergence of crabgrass typically occurs when the ground gets to be about 55°F, and most seeds germinate between 60°F and 70°F.

It’s crucial to understand soil temperatures to time your preemergence applications properly. Having soil temperatures over 55 degrees means more than simply having high temperatures.

It takes a lot more than a sunny day to raise soil temperatures.

The air temperature will need to have sustained warm temperatures for multiple days in order to begin raising the soil temperatures. This includes nighttime temperatures as well.

You may consider finding an online soil temperature map for general temperatures in your area, or you can purchase a soil thermometer for an more specific reading.


Pre-emergent is a very effective form of weed control. It can be distributed across an entire lawn, and effectively prevent weeds while leaving the established grass unharmed in any way.

Remember that pre-emergent stops all plant types from sprouting, including any grass seed you spread. Do not seed your lawn at the same time you are applying a crabgrass preventer.

The disturbed soil can make the product less effective and the product will also prevent the seeds from taking root.

If you have already seeded the lawn, a good rule of thumb is to wait for 2-3 mows until applying preemergent. Apply granular formulas right before rain is forecast so that the rain can help water the preventer into the soil.

Apply it uniformly across your lawn, making sure not to miss any spots.

Once applied, you’ll need to hydrate your lawn consistently to ensure the preemergent is absorbed into the soil. This can be either from rainfall or from water distributed from your sprinkler system.

This step is crucial to the success of the product.

If it does not rain, make sure to turn on your sprinklers. It may seem strange to water the lawn in January or February, but your summer self will thank you later.

Check out our article on the importance of pre-emergent weed control if you would like to learn more. 

FYI Pre-emergent and post-emergent weed controls can be used simultaneously. In the South, you have to do whatever it takes to reclaim your yard.

Too Late?

If you do not apply the crabgrass preventer in time, do not panic. There is still hope to eliminate the weeds as they come up.

Although it is difficult, crabgrass can be treated after they emerge. 

Trust a local lawn professional to treat those weeds with expert care. Gecko Green has been tackling crabgrass in North Texas Lawns since 2001.

Our team of expert lawn technicians know with certainty how the right timing in North Texas to apply preemergent effectively and to treat weeds so you do not have to battle weeds all year long.

Request a free lawn care quote today!