When to put down Pre-Emergent Crabgrass Weed Control

When to Apply Pre-Emergent Crabgrass Control in Central New Jersey

(Skillman, Belle Mead, Hillsborough, Princeton, Hopewell, and Pennington, NJ)

Spring is the perfect time to prepare your lawn for a healthy growing season. One of the most effective strategies is applying pre-emergent herbicides to prevent weeds like crabgrass and Japanese stiltgrass from taking root.

Why Pre-Emergent Crabgrass Control Is Important

Crabgrass is an annual weed that competes with your lawn for nutrients, water, and sunlight. Timing your pre-emergent application is critical because these products eliminate weeds at the earliest stage of growth—before you can even see them.

Similarly, Japanese stiltgrass (Microstegium vimineum) is an invasive species introduced to the U.S. in the early 1900s, likely as packing material from Asia. It spreads rapidly in both sunny and shaded areas, outcompeting native plants and grasses. Applying pre-emergent herbicides early in the season can significantly reduce stiltgrass infestations before they become a problem.

The Best Time to Apply Pre-Emergent in New Jersey

When it comes to applying pre-emergent herbicides in Central NJ, timing is crucial. Here's the best approach to ensure effective control of weeds like crabgrass:

1. Soil Temperature: The most reliable indicator is the soil temperature. Each year, crabgrass seeds begin to germinate when nighttime soil temperatures reach over 50°F for three consecutive days. This "wakes up" the seed and starts the process of your worst nightmare—an invasion of crabgrass taking over your lawn. In our area, this typically occurs sometime in late April or May.

2. Early Application: It's better to apply pre-emergent before the soil reaches 50°F, especially if the forecast indicates that temperatures are rising. This ensures that the herbicide is in place right before weed germination begins.

3. Second Application: For extended control, consider applying a second round of pre-emergent 6-8 weeks after the first application. This helps to prevent late-season weeds and ensures your lawn remains protected throughout the growing season. This is standard in Green Valley 6-Step Lawn Care programs!!!

By focusing on soil temperature rather than old timing methods, you can maximize the effectiveness of your pre-emergent treatments and keep your lawn weed-free.

Choosing the Right Pre-Emergent Product

Using the right product ensures effective weed control:

• Prodiamine (Barricade): Offers long-lasting control and is best applied early.
• Dithiopyr (Dimension): Provides some post-emergent control if crabgrass or stiltgrass has just begun germinating.
• Pendimethalin: Effective but may require multiple applications due to faster degradation.

 Since it has some post-emergent control, using Dithiopyr gives you a much larger window to apply the pre-emergent while still getting great control.

Post-Emergent Crabgrass Control: Considerations and Cautions

If crabgrass has already emerged, post-emergent herbicides are available, but they come with important considerations:

• Chemical Potency: Many post-emergent herbicides contain potent chemicals that can affect desirable grass species if not applied correctly.
• Visual Impact: Some herbicides, such as those containing mesotrione, can cause bleaching of crabgrass, turning it white and potentially creating an eyesore on your lawn.
• Application Timing: Post-emergent treatments are most effective when applied to young, actively growing weeds.

Given these factors, relying on pre-emergent applications is the preferred strategy for maintaining a healthy lawn and avoiding the need for tougher post-emergent treatments.

Application Tips for Best Results

To get the most out of your pre-emergent herbicide:

1. Apply Before Germination: Ensure the pre-emergent is applied before crabgrass and stiltgrass seeds germinate.
2. Water It In: Lightly water your lawn after application to activate the pre-emergent and facilitate soil absorption.
3. Avoid Disturbing the Soil: Refrain from aerating or dethatching after application, as this can disrupt the pre-emergent barrier.
4. Maintain Proper Mowing Practices: Keep your grass at a height of 3-4 inches to shade out potential weed growth.
5. Consider Split Applications: If your lawn had significant weed issues last year, a second application in late spring can help prevent breakthroughs. (Standard in Green Valley's 6-Step Lawn Care programs!)

What If You Miss the Pre-Emergent Window?

If weeds have already emerged, post-emergent herbicides may help, but they are generally less effective and can pose risks to your lawn’s health. Maintaining thick, healthy turf through proper mowing, fertilization, and watering is the best defense against weed invasions.

Final Thoughts

Applying pre-emergent herbicides at the right time is crucial for preventing crabgrass and Japanese stiltgrass infestations. By following these guidelines, you can enjoy a lush, weed-free lawn throughout the growing season.

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