When to Apply Spring Pre-Emergent: Best Time for Spring Weed Control

Applying a spring pre-emergent, when done properly, can be one of the most significant and satisfying tasks you complete all year when it comes to the appearance and health of your lawn.

Too often our hard work in the spring months can be derailed by the appearance of crab grass and other weeds once the weather warms. Let’s take a look at when and how to properly apply pre-emergent effectively this spring, to avoid those nasty warm-weather weed takeovers come summer.

Key Takeaways

• Pre-emergent herbicides need to be applied when soil temperatures reach around 55 degrees Fahrenheit.
• Choosing the correct product and following best application practices are crucial for effectiveness.
• Post-application lawn maintenance ensures ongoing health and weed resistance.

Understanding Pre-Emergent Herbicides

When you’re preparing your lawn for the spring, understanding how pre-emergent herbicides can prevent weeds is crucial. These herbicides create a barrier that inhibits weed growth, ensuring your lawn remains healthy and attractive.

Types of Pre-Emergent Herbicides

There are primarily two forms of pre-emergent herbicides that you can choose from: liquid pre-emergent and granular pre-emergent. The liquid form is applied using a sprayer and can be more evenly distributed, whereas the granular form is applied using a spreader and may require watering to activate. Each type contains active ingredients that prevent the growth of weeds.

How Pre-Emergent Herbicides Work

Pre-emergent herbicides function by creating a chemical barrier at the soil level that disrupts the growth process of weeds. They target weeds during the germination phase, which is before the weeds surface above the ground. Remember, the treatment won’t kill existing weeds; it’ll only prevent new ones from sprouting. Timing and proper application are critical—the barrier needs to be in place before the soil temperature reaches a level conducive to weed seed germination.

Optimal Timing for Spring Application

To ensure the effectiveness of your spring pre-emergent herbicide, paying attention to soil temperature and weather patterns is crucial.

Soil Temperature and Weed Germination

Soil temperatures around 55 degrees Fahrenheit sustained for at least 48 hours signal that it’s time for your spring pre-emergent application. This threshold is a reliable indicator that weed seeds are ready to germinate. Check the soil temperature with a thermometer in the early morning for the most accurate reading.

Weather Patterns and Rainfall

Aligning pre-emergent application with the local weather patterns helps to maximize its efficacy. Apply the herbicide when there is no significant rainfall expected for at least 48 hours post-application. This allows the product to properly adhere to the soil without being washed away. For optimal absorption, apply the pre-emergent just before a light rain, which helps integrate the herbicide into the soil layer.

Selecting the Right Product

Before deciding on a pre-emergent herbicide for spring application, consider the formulation and chemical composition best suited for your lawn care needs. These factors determine the effectiveness and ease of application.

Liquid vs. Granular Pre-Emergents

Liquid Pre-Emergents are ideal for uniform application. They’re typically applied using a sprayer, allowing you to cover areas precisely and adjust the mix to suit your lawn’s specific requirements. Granular Pre-Emergents provide a convenient, spreadable option, often preferred for larger areas. They require a broadcast spreader and can be a time-saver, as they are less likely to need mixing like their liquid counterparts.

Chemical Considerations

Different active ingredients in pre-emergent herbicides target various weed types and growth stages. Dithiopyr is effective at controlling crabgrass as well as other broadleaf weeds and grasses. It’s not just a pre-emergent but also offers early post-emergence control.

Prodiamine is a widely used option due to its long residual activity in the soil, providing season-long control. For broad-spectrum weed control, including broadleaf weeds and grassy species, Isoxaben is known for its efficacy.

Consider Benefin for a reliable, albeit more limited, spectrum of control, particularly for grasses. Oxadiazon is appreciated for its safety on certain turfgrass types while combating a range of pre-emergent weeds. If your intention is to hinder the growth of a variety of common annual grasses and broadleaf weeds, Trifluralin could be a part of your management strategy.

Each chemical has its specific use cases and limitations, so always read the label and comply with application guidelines to ensure the best results for your particular lawn situation.

Application Techniques and Best Practices

Ensuring the success of your pre-emergent herbicide application largely depends on using the correct techniques for even distribution and coverage. Understanding your tools and the product’s instructions is crucial for effective weed control.

Calibrating Spreaders for Even Distribution

When using a broadcast spreader or a drop spreader, you must calibrate it properly to achieve even application of the herbicide. Follow these steps:

1. Refer to the herbicide label for the recommended application rate.
2. Fill the spreader with the pre-emergent herbicide.
3. Adjust the spreader settings according to the manufacturer’s instructions to match the application rate.
4. Test the spreader over a known area (e.g., 1,000 square feet) to ensure the output matches the suggested rate. If necessary, make adjustments.
5. Once calibrated, walk at a steady pace to ensure an even distribution across your lawn.

Applying Pre-Emergent in Lawn and Landscape Areas

To maximize the effectiveness of pre-emergent herbicides in your lawn care routine, use them judiciously in both lawn and landscape areas.

• Use a sprayer for liquid herbicide application, ensuring that the nozzle provides a uniform spray pattern. Start spraying the pre-emergent herbicide on a calm day to prevent drift and achieve precise application.
• When applying around ornamentals and in landscape beds, a granular formula with a drop spreader is often preferred to prevent granules from scattering into plant areas.
• For optimal coverage, apply granular pre-emergent in perpendicular passes, first lengthwise and then widthwise across the area.
• Water the product in as advised on the label to activate the herbicide.

Consistency in your application technique is key to a uniform barrier against weeds and contributes substantially to your overall lawn care strategy.

Maintaining a Healthy Lawn After Application

After applying a pre-emergent to your lawn, the key to sustaining a healthy turf is a proper maintenance routine. Focused watering, fertilizing, mowing, and reseeding considerations are critical to fostering robust grass and root development.

Watering and Fertilizing

Once pre-emergent is applied, water your lawn carefully to activate the herbicide and encourage its penetration into the soil. Aim for 1 inch of water per week, either through rainfall or irrigation, to maintain optimal moisture levels without over-saturating the soil. Fertilizing should follow the product’s guidance; apply a balanced fertilizer to nourish your grass and improve soil fertility, enhancing your lawn’s resilience against weeds.

Mowing and Reseeding Considerations

Mowing helps maintain turf health but requires timing and technique. Allow the grass to reach 3 inches in height before cutting to no less than 2 inches. This practice protects the root system and maintains a dense lawn that stifles weed growth. When thinking about reseeding, wait for the effects of the pre-emergent to diminish to ensure new seeds are not inhibited, which typically means waiting until the next recommended planting season.