The Importance of Pre-Emergent Herbicide Applications in Weed Control

Florida’s wet and humid climate can make for some of the most lush landscapes in the country. But those same conditions are also perfect for aggressive weeds that can quickly get out of hand. Invasive weeds can overtake even the most meticulously maintained properties, choking out ornamental grass, crowding colorful hibiscus beds, and diminishing the overall health of your landscape.

To fight back, most homeowners consider pre-emergent herbicides as their first line of defense. As professionals, we agree this is the smart choice, as fighting weeds before they become an issue is always better than battling them once they’ve started to crowd out your grass.

In this post, we’ll explain what pre-emergence herbicides are, how they work, and how you can best use them to keep weeds under control all year long.

What Are Pre-Emergent Herbicides and How Do They Work?

Pre-emergent herbicides prevent the germination of the weed seeds. The herbicide creates a type of barrier in the soil, preventing weeds from growing in the first place.

Herbicides are sometimes categorized based on what stage of weed growth they are effective against. The two categories are pre-emergent (before weeds emerge) and post-emergent (seedlings or full-grown).

When pre-emergent herbicides are applied correctly, they prevent cell division and stop seeds from forming roots and spreading throughout the soil. These herbicides can be used preventively to stop crabgrass, spurge, Florida pusley, invasive goosegrass, and other weeds.

As the name suggests, these only work as a preventive measure. Using pre-emergent pesticides when invasive species or weeds have already taken hold won’t work.

You should think of pre-emergent herbicides solely as a prevention, not a cure.

Why Timing Matters in Weed Prevention

In life, they say timing is everything. When it comes to Florida weed prevention, this couldn’t be truer. Florida’s extended growing seasons and mild winters mean that weed seeds can germinate nearly year-round, which requires a more nuanced approach to pre-emergent application.

Since the goal is to prevent seed germination, you want to target a time before the seeds typically germinate. Because of this, soil temperature can be used as a guide for application timing. For certain aggressive weeds that begin taking hold in early spring, soil temperatures that hit 55-60 degrees Fahrenheit will trigger germination.

For certain fall applications, you want to apply pre-emergents before the soil temperature falls below 70 degrees. Missing these windows by just a week or two can mean the difference between success and failure. If the window is missed, the seeds have already germinated, and the application will have been useless.

Most Florida lawn care professionals with experience in pre-emergents will recommend two applications, one in the early spring and another in the fall. This captures these two critical windows and provides maximum protection for the lawn.

Lawns with previous problems with certain weeds or invasive species can modify the application schedule to deal with specific circumstances.

Recommendations for Applying Pre-Emergents

For application, you generally want to prepare the grass by cutting it to the recommended length for your specific grass, which is typically 3.5 to 4 inches. Since pre-emergents work as a type of soil barrier, the product needs to reach the soil, and long grass blades can prevent that. This can force you to use more product than needed, or it can cause the product to fail to reach the soil.

There are two main types of pre-emergent products: Granular and liquid.

Granular Application: Use a broadcast spreader for large turf areas and a drop spreader for precise application around delicate tropical plantings. Apply when the grass is dry to avoid the product from sticking to the blades of grass. Watering is needed within 24-48 hours of application to ensure the product reaches the soil successfully.

Liquid Application: Liquid applications are usually more common when using a professional lawn care service. Liquids can have advantages for mulch beds or other decorative areas that require better penetration to reach the soil. Similar to granular products, liquid applications require that they be watered in within 24-48 hours. Only moderate watering is needed, as too much will wash away the product.

For enhanced pre-emergent results, consider adding Dithiopyr 2EW and Sustain. Dithiopyr 2EW prevents the germination of weeds like crabgrass and goosegrass, while Sustain improves herbicide penetration, ensuring better coverage and effectiveness in tough conditions.

Learn more about Dithiopyr 2EW and Sustain.

Common Mistakes to Avoid When Using Pre-Emergents

Pre-emergents can be incredibly useful for preventing weed growth before the signs become visible. However, homeowners often make a few common mistakes that really detract from how effective these herbicides can be.

Below, we’ll outline the most common mistakes to avoid when using a pre-emergent on your Florida lawn.

Using Pre-Emergents on New Grass or Lawns

One common mistake is to apply pre-emergents on a very new property or lawn area. While this can seem like a good preventative measure, it can actually harm the grass. Pre-emergents can interfere with all seed germination. This means pre-emergents used on a new lawn or property can harm the grass seed germination as well.

Typically, you’ll want to wait up to 4 months after a new lawn takes hold before considering a pre-emergent. However, this can vary depending on the grass variety and herbicide product chosen.

Aerating or Dethatching Too Soon

Remember, pre-emergents work like a soil barrier for your precious lawn and landscaping. Aerating, detaching, or disrupting the soil breaks this barrier, creating an inviting path for weeds to take hold.

A professional lawn care service will understand this, but if maintaining your own lawn, perform these activities before applying the pre-emergent.

Not Watering or Watering Too Much After Application

Whether liquid or solid, these products will need water after application to reach the soil. Consult the manufacturer’s instructions for exactly how much water is needed and how soon after application is best. Getting this wrong can prevent the herbicide from working, which wastes time, money, and exposes your lawn to more chemicals than needed.

Relying on Pre-Emergents Too Much

It seems like the perfect strategy. Invest in pre-emergents at the right time, and you’ll never have to deal with weed growth. But in practice, weeds always find a way, especially in Florida. This is why pre-emergents should be just one part of a comprehensive strategy tailored for your lawn, grass types, and specific invasive weeds.

Get Expert Help With Pre-Emergent Use and Strategies

If you’re considering pre-emergent use on your Florida lawn, contact our lawn care experts. We can analyze your problem and suggest the best course of action to maintain a lush lawn that’s free from weeds and invasive grass varieties year after year.