Can Crabgrass Preventer Harm New Grass?

Will crabgrass preventer kill new grass? It’s a common concern for homeowners who are eager to achieve a lush, green lawn. The last thing you want is to spend time and effort nurturing new grass only for it to be destroyed by crabgrass preventer. But fear not! In this article, we will explore whether crabgrass preventer is a friend or foe to your new grass. By the end, you’ll have all the answers you need to ensure the health and vitality of your lawn. So, let’s dive right in and put this query to rest once and for all.

Can Crabgrass Preventer Harm New Grass?

Will Crabgrass Preventer Kill New Grass?


Crabgrass is a frustrating and persistent weed that can quickly take over a lawn if left unchecked. As homeowners strive to maintain a lush and healthy lawn, they often wonder if using a crabgrass preventer will harm their newly planted grass. In this article, we will delve into the topic of whether crabgrass preventer can kill new grass, providing you with a comprehensive understanding of the potential impacts and how to navigate this common concern.

Understanding Crabgrass Preventer

To fully comprehend the effects of crabgrass preventer on new grass, it’s essential to understand what it is and how it works. Crabgrass preventer is a pre-emergent herbicide designed to inhibit the germination and growth of crabgrass seeds. It forms a chemical barrier in the top layer of soil, preventing the weed seeds from sprouting and establishing. While crabgrass preventer is highly effective in controlling crabgrass, it may also have implications for newly planted grass if not used correctly.

The Mode of Action

Crabgrass preventer typically contains active ingredients like dithiopyr, pendimethalin, or prodiamine. These chemicals work by forming a barrier on the soil surface that inhibits the growth of crabgrass roots. As the herbicide is applied, it creates a thin film that prevents the weed seeds from absorbing water and essential nutrients, ultimately causing them to perish. However, when new grass seeds are also present, the herbicide has the potential to affect their establishment.

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The Impact on New Grass

While crabgrass preventer is primarily formulated to target crabgrass seeds, it can inadvertently affect newly planted grass seeds as well. Here are some factors to consider:

Timing of Application

The timing of applying crabgrass preventer is crucial to minimizing the impact on new grass. If you plan to grow new grass from seeds, it is recommended to wait until the new grass has established a root system before applying a crabgrass preventer. This usually takes around six to eight weeks. Applying the herbicide too early can interfere with the germination and growth of the new grass, resulting in poor establishment or even death.

Species of Grass

Different grass species have varying levels of sensitivity to herbicides. Some are more tolerant, while others can be significantly affected even at lower concentrations. It is essential to identify the specific type of grass you have planted and research its sensitivity to herbicides. This information will help you determine the best approach to using a crabgrass preventer without harming your newly planted grass.

Application Rate and Formulation

Following the instructions on the crabgrass preventer package is vital to avoid excessive application rates that could harm new grass. Applying more than the recommended amount can increase the absorption of the herbicide, potentially affecting both crabgrass seeds and new grass seeds. Additionally, different formulations may have varying effects on new grass, so it is important to choose a product that is suitable for your lawn’s specific needs.

Minimizing Risks and Ensuring Success

While there are potential risks involved in using crabgrass preventer when new grass is present, there are steps you can take to minimize these risks and ensure successful establishment of your lawn:

Selective Herbicides

Consider using selective herbicides that specifically target crabgrass while allowing new grass to flourish. These products are designed to minimize the detrimental effects on desirable grass species, providing a safer option for weed control without compromising the growth of your newly planted grass.

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Spot Treatment

If you notice crabgrass starting to invade your lawn after seeding, consider spot treating the affected areas rather than applying a blanket application of crabgrass preventer. This targeted approach will eliminate the weed while minimizing exposure to the new grass.

Watering and Fertilization

Proper watering and fertilization practices can help promote the growth and establishment of newly planted grass while minimizing the impact of crabgrass preventer. Adequate watering, based on your specific grass type’s needs, will help flush any residues leftover from the herbicide application. Additionally, providing a balanced fertilization regimen will enhance the overall health and vigor of your lawn, making it more resilient to potential herbicide effects.

Professional Advice

If you are uncertain about using a crabgrass preventer on your newly planted grass, it is always advisable to seek professional advice from a lawn care expert or your local agricultural extension office. They can provide personalized recommendations based on your specific lawn conditions and guide you through the process of weed control while safeguarding the health of your new grass.

While crabgrass preventer can potentially impact newly planted grass, understanding the proper timing, grass species sensitivity, and appropriate application techniques can minimize the risks associated with its use. By following the recommendations outlined in this article and seeking professional guidance when needed, you can effectively manage crabgrass while nurturing the growth of your new grass. Remember, a healthy and vibrant lawn requires a balanced approach to weed control and proper lawn care practices.

Help Me, BHG: Can I Apply Crabgrass Preventer and Grass Seed at the Same Time?

Frequently Asked Questions

Will crabgrass preventer kill new grass?

No, crabgrass preventer generally does not kill new grass. However, it is important to follow the instructions on the product label and properly apply the crabgrass preventer to avoid any potential damage to newly seeded or recently established grass.

How does crabgrass preventer work?

Crabgrass preventer forms a protective barrier on the soil surface, creating a barrier that prevents crabgrass seeds from germinating. It does not kill existing weeds but stops new weeds, such as crabgrass, from growing.

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When should I apply crabgrass preventer in relation to seeding new grass?

It is generally recommended to wait until the new grass has been mowed three to four times before applying crabgrass preventer. This allows the grass to establish a strong root system and minimizes the chances of any potential damage from the preventer.

Can crabgrass preventer harm other types of grass?

Crabgrass preventer is generally safe for most grass types when applied according to the instructions. However, some sensitive grass species such as St. Augustinegrass and Buffalograss may be more susceptible to damage. It is best to check the product label for specific information regarding compatibility with different grass types.

Should I use a crabgrass preventer if I have recently overseeded my lawn?

If you have overseeded your lawn recently, it is generally recommended to avoid using crabgrass preventer. The preventer can also inhibit the germination and growth of desirable grass seeds, potentially affecting the results of overseeding. It is best to wait until the newly seeded grass has fully established before applying crabgrass preventer.

How long does the crabgrass preventer remain effective?

Most crabgrass preventers provide protection for about 8 to 12 weeks after application. However, this can vary depending on environmental conditions and the specific product used. It is generally advisable to reapply the preventer if crabgrass is still a concern after the initial application period.

Final Thoughts

Crabgrass preventer can pose a risk to new grass. If applied incorrectly, it can hinder the growth of new grass seeds. However, when used as directed and at the right time, crabgrass preventer can effectively control crabgrass without killing new grass. It creates a barrier that prevents crabgrass seeds from germinating while allowing the growth of desirable grass species. So, if you’re wondering, “Will crabgrass preventer kill new grass?” rest assured that when used correctly, it can protect your lawn without causing harm to your newly planted grass.