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When to Water After Pre-Emergent? | A Helpful Guide!

A thriving, lush green lawn is a homeowner’s pride.

But achieving and maintaining it requires careful attention and strategic care.

Weeds—the relentless invaders, can quickly sabotage even the most well-manicured landscapes.

That’s where pre-emergent herbicides come into play, providing a powerful defense against unwanted weeds.

Applying pre-emergent herbicides to your lawn can be an effective way to control weeds and unwanted grasses.

However, to maximize the effectiveness of these herbicides, it’s crucial to understand the optimal timing for watering after pre-emergent application.

Watering too soon can wash away the herbicide while waiting too long can result in poor weed control.

But you don’t need to be anxious about anything.

In this article, unlock the secrets to a thriving lawn, discover when to water after pre-emergent, and ensure a thriving green lawn.

Let’s dive in!

When to Water After Pre-Emergent
When to water after pre-emergent? | Image via Unsplash

When to Water After Pre-Emergent?

So, when to water after pre-emergent?

After applying pre-emergent herbicides to your lawn, watering at the right time is essential to ensure effective weed control.

In general, waiting at least 24 to 48 hours after applying pre-emergent herbicides before watering your lawn is recommended. This timeframe allows the herbicide to settle into the soil and create a barrier that prevents weed seeds from germinating.

However, the timing of watering may depend on various factors, such as:

  • Type of pre-emergent herbicide
  • Temperature 
  • Soil type

Some pre-emergent herbicides may require a shorter or longer waiting period before watering.

So, it is crucial to read the label instructions carefully before applying the herbicide and follow the recommended watering guidelines.

Growgardener’s NOTE: It is essential to water your lawn deeply and infrequently after applying pre-emergent herbicides.

This method,

  • Encourages profound root growth.
  • Helps the herbicide stay in place.
  • Provides effective weed control.

Avoid frequent shallow watering, which can wash away the herbicide and lead to poor weed control.

When Do You Need to Apply Pre-Emergent?

If you seek effective management of the annual grassy weeds that emerge during the late spring or early summer, like Crabgrass or Foxtail, the first lawn care treatment is the pre-emergent application.

Getting my point?

The fact behind doing this is to do treatment and kill the nasty weeds before they emerge.

It just works like a vaccine for the grass!

But when do you need to apply these pre-emergent herbicides?

Well! There are certain things you need to consider before applying any pre-emergent; these include the following:

Life Cycle of Weeds

It’s essential to understand the life cycle of weeds to comprehend the significance of pre-emergent herbicides.

Weeds typically reproduce and spread through seeds, which lie dormant in the soil until favorable conditions prompt their germination.

By strategically targeting these seeds before they sprout, pre-emergent herbicides effectively halt weed growth at its earliest stage, providing a solid foundation for a weed-free lawn.

Seasonal Timing

To prevent weeds from sprouting, you need to apply pre-emergent fertilizers.

The best time to apply pre-emergent herbicides depends on the types of weeds that commonly grow in your area and when they tend to sprout.

Generally, pre-emergent herbicides should be applied before the target weeds’ seeds germinate.

Timing can vary based on location and climate.

So, it is better to consult local gardening resources or seek advice from lawn care professionals in your area.

Soil Temperature

Soil temperature plays a vital role in determining when to apply pre-emergent herbicides.

Different weed species have distinct temperature thresholds for germination.

Monitoring the soil temperature using a soil thermometer can provide valuable understanding.

Generally, measuring the temperature during the hottest part of the day is recommended, and applying the pre-emergent when it hits above the ’40s.

How to Apply Pre-Emergent Herbicides?

There are different ways to apply pre-emergent herbicides, which depend on the type of pre-emergent you get.

There are two main types of pre-emergent:

  1. Liquid pre-emergent
  2. Granular pre-emergent.

Let’s discuss how you can apply each of the different types. 

Liquid Pre-Emergent

Liquid pre-emergent is generally easier to apply over large areas like lawns since you can use a sprayer.

Mixing and uniformly applying the mix is crucial to make your liquid pre-emergent work properly.

Some liquid pre-emergent products are concentrates, meaning you must dilute them with water before applying, so read your product’s label carefully.

When to water after pre-emergent
When to water after pre-emergent? | Image via Balazs Simon

Granular Pre-Emergent

Granular pre-emergent herbicide is less convenient to use for lawns and requires the use of a drop spreader.

You can apply granular pre-emergent without a spreader, although doing so runs the risk of uneven coverage.

  • Apply when the grass is dry.
  • Set the spreader to the appropriate settings as per instructions.

Usually, granules do not need to be watered. But for the best results, water your lawn about a half inch within 2–3 days of application.

If you already own a spreader, granular pre-emergent is the more flexible option.

Although most granular pre-emergent is more expensive than its liquid counterpart, as long as you apply both types correctly, both types of pre-emergent are equally effective at preventing weed growth.


Here are the answers to some frequently asked questions.

Why Is Watering After Pre-Emergent Application Necessary?

Watering after the pre-emergent application is necessary to activate and evenly distribute the herbicide throughout the soil.

It ensures that the weed-preventing barrier is properly established.

Adequate watering also helps the herbicide reach the weed seeds, increasing its effectiveness and providing better control against unwanted weed growth.

Can I Water My Lawn Before Applying Pre-Emergent?

Watering your lawn immediately before applying pre-emergent herbicides is generally not recommended.

The soil should be dry before application to allow the herbicide to adhere to the surface and penetrate the soil properly. Watering before application may dilute the herbicide’s effectiveness and reduce its ability to create a weed barrier.

What if It Rains After I Apply Pre-Emergent?

If it rains shortly after applying pre-emergent herbicides, you may not need to water again.

However, if the rainfall is light or insufficient, it is advisable to supplement it with additional watering.

Adequate moisture is necessary to activate the herbicide and ensure its proper distribution in the soil for effective weed control.

That’s all!

Let’s now explore the conclusion of the article.


I hope now you know when to water after pre-emergent.

Generally, it would be best to wait 1 to 2 days to water your lawn after applying pre-emergent herbicides.

The best time to apply pre-emergent herbicides depends on various factors like seasonal timing and the corresponding temperature. The method to apply these pre-emergents varies depending on the type of it you are using.

After understanding all this, you are ready to take control of you of your lawn and bid farewell to pesky weeds.

Implement these tips and start your journey towards a vibrant, weed-free lawn today.

Moiz Atiq.