What is Preemergent and When Should You Apply It?

Even the healthiest lawns can fall victim to unwanted weeds. The smartest way to stop them is before they sprout, and that’s where preemergent herbicides come in.

Preemergent herbicides form the foundation of effective weed control. They target newly germinated weeds before they emerge, helping your turf stay thick, vibrant and free of invasive growth. Timing, however, makes all the difference. Applying preemergent too early or too late can limit its effectiveness, which is why understanding how and when to use it is so important.

In this guide, we’ll cover everything you need to know, including:

• What preemergent herbicides are and how they work.
• When and how to apply them for the best results.
• Common mistakes to avoid.
• Environmentally responsible and properly used options.

With TruGreen’s nationwide expertise and localized care, your lawn receives customized preemergent treatments designed for your grass type, soil and climate conditions, ensuring protection all season long. 

A preemergent herbicide is a weed preventer that targets newly germinated weeds before they emerge. Unlike post-emergent herbicides, which attack existing weeds, preemergents form a barrier beneath the soil surface to block new weeds from taking root or breaking through.

Because preemergents stop weeds at their earliest life cycle stage, they’re among the most effective tools for maintaining a thick, even lawn. By keeping weeds from competing with your grass for sunlight, nutrients and water, they help your turf look consistently healthy and green. 

Think of preemergent herbicides as a shield for your lawn. When applied correctly, they create a thin barrier in the soil that stops weed seeds before they have a chance to grow. As seeds begin to sprout, their tiny shoots absorb the herbicide, which interrupts early development, so weeds never make it to the surface.

Water is key to making that barrier work. After applying a preemergent, light irrigation or rainfall helps it soak into the soil and activate. Once in place, it keeps protecting your lawn for months, or long enough to get you through an entire growing season, depending on your soil, grass type and local weather.

TruGreen specialists tailor each application to your specific lawn conditions. They look at soil composition, temperature and regional weed patterns to make sure the treatment goes down at the right time and in just the right amount. Their precise methods keep your lawn healthy while stopping weeds before they can start. 

The key to preemergent success is timing. These products work before weeds appear, not after. Once you spot weeds popping up, it’s too late for prevention, so you’ll need a post-emergent treatment instead.

In most areas, a spring application targets summer weeds like crabgrass, foxtail and goosegrass. These usually start germinating once soil temperatures reach about 55°F for several days in a row, so applying a preemergent just before then gives you the best results.

A fall application helps protect against cool season weeds such as chickweed, henbit and annual bluegrass. Treating early in the season ensures the barrier is already active when cooler weather sets in.

Regional climate also affects how often you’ll need treatments.  

• In the South, lawns may need spring and fall preemergent applications because of the longer growing season.
• Northern lawns often do well with one or two carefully timed treatments in the spring.  

TruGreen’s local experts monitor soil temperatures and seasonal trends to make sure your lawn gets exactly what it needs - no guesswork required. 

Applying preemergent herbicide correctly makes all the difference. Each product’s success depends on even coverage, proper activation and minimal soil disturbance. Here’s a simple guide:

• Choose the right product for your grass type, weed challenges and lawn conditions.
• Mow and clear debris so the product can reach the soil surface evenly.
• Apply uniformly using a calibrated spreader or sprayer to avoid patchy coverage.
• Water lightly to activate the barrier; this is a crucial step for effectiveness.
• Avoid disturbing the soil after treatment to keep the barrier intact.
• Reapply as directed on the product label or as the barrier begins to fade.

While homeowners can apply preemergent on their own, precise timing and coverage can be tricky. TruGreen professionals handle these details for you, using advanced equipment and commercial-grade formulations to achieve consistent, season-long protection. Contact your nearest TruGreen lawn care pro, or check out our service plans here. 

Preemergent herbicides are available in granular and liquid forms, each suited to different lawn care needs.

• Granular preemergents: Ideal for large, even lawns and easy for homeowners to apply. The granules distribute evenly with a spreader and are activated by water or irrigation.
• Liquid preemergents: Provide faster absorption and precise control, making them a preferred option for professional applications or targeted areas.

TruGreen uses commercial-grade formulations engineered for uniform results across any lawn or landscape. Whether granular or liquid, these products are applied with precision to ensure consistent coverage, durability and protection for your turf. 

Using preemergent herbicides offers long-lasting benefits that extend beyond simple weed prevention:

• Stops weeds before they appear, supporting dense, healthy turf.
• Reduces reliance on post-emergent herbicides and reactive weed control.
• Limits competition for vital nutrients, sunlight and water.
• Maintains your lawn’s uniform color and density throughout the season.
• Saves time, money and effort with proactive care rather than constant repair.

For homeowners who value curb appeal and want a lawn that enhances their property’s appearance, preventive care is key. Learn more about how lawn treatments can enhance curb appeal and boost your home’s value. 

When it comes to weed control, homeowners often want to know more about the products used on their lawns. TruGreen follows a careful selection process to determine which products are applied. Every product we use is registered for residential use by the U.S. Environmental Protection Agency (EPA), and in many cases, our internal standards go beyond EPA requirements.

TruGreen specialists apply EPA-registered products chosen for their proven performance and suitability for the most common turf types. Each application follows detailed label directions and responsible environmental practices to help lawns stay healthy and resilient.

After a TruGreen treatment, your specialist will share instructions for watering, reentry and other follow-up care. Following these steps helps ensure the treatment works as intended and provides even, consistent results across your lawn.

Pro Tip: If you choose to apply a preemergent yourself, always read and follow the manufacturer’s directions carefully. 

Even a great product can fail if applied incorrectly. Avoid these common preemergent mistakes:

• Applying too late after the weed seed has germinated.
• Skipping the watering step needed for activation.
• Overlapping or missing areas during application.
• Disturbing the soil too soon afterward.
• Choosing the wrong herbicide for your grass type.

These errors can create uneven results and leave your lawn vulnerable to grassy weeds and broadleaf species. TruGreen’s professional technicians eliminate these challenges with precise application methods and expert timing for reliable, season-long control.

For more advice on proper lawn care, explore TruGreen’s top tips for avoiding common lawn care mistakes. 

Preventing weeds before they sprout is the smartest, most effective way to maintain a lush, resilient lawn. Preemergent herbicides act as the first line of defense in your weed control plan, protecting your turf from invasive growth all year long.

Whether you’re dealing with crabgrass, chickweed or other seasonal weeds, TruGreen’s team uses premier products, regional expertise and proven timing strategies to keep your lawn healthy and strong.

Explore TruGreen’s expert services today to discover how a customized lawn care plan can help your yard look its best every season.