what are pre-emergent herbicides

What are Pre-Emergents & When to Apply

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Keeping your lawn healthy and weed-free in North Texas requires a proactive approach. If you’re new to lawn care, you have probably heard the buzz word, pre-emergents. What exactly are pre-emergent herbicides? Understanding how these herbicides work and the best times to apply them is important.

What Are Pre-Emergent Herbicides?

Pre-emergent herbicides are chemicals designed to prevent weed seeds from germinating.  Pre-emergents create a barrier in the soil that stops weeds before they become visible. They are highly effective at preventing new ones from taking over your lawn. Post-emergent herbicides kill weeds after they have sprouted.

University of Nevada (n.d.) Preemergence herbicides, on the other hand, are applied before weed seeds germinate. They are used to control annual grass and broadleaf weeds. 

what are pre-emergents?
Effortlessly distribute granular pre-emergent herbicides with a broadcast spreader.

How to Choose a Pre-Emergent

When choosing a pre-emergent herbicide, it’s essential to look for key active ingredients that effectively prevent weed growth.
Some of the top ingredients include pendimethalin, which inhibits cell division in weeds. Prodiamine, is known for its broad-spectrum control of grassy and broadleaf weeds.
Dithiopyr is another popular choice, offering both pre- and post-emergent control, while alachlor targets annual grasses and broadleaf weeds.
Additionally, flumioxazin is effective for controlling certain tough weeds, including those that thrive in higher-moisture conditions.
Selecting a pre-emergent herbicide with the right active ingredient for your specific needs will significantly improve weed control and reduce the need for chemical applications later in the season.

When to Apply Pre-Emergent Herbicides in North Texas

Timing is everything when it comes to pre-emergent herbicide application. In North Texas, there are two critical application windows:

  • Spring Application (February – March): This application targets summer weeds like crabgrass and dallisgrass before they have a chance to germinate. Apply pre-emergents when soil temperatures reach around 55°F for several consecutive days, usually in mid to late February to early March.
  • Fall Application (September – October): This helps control winter weeds like henbit and annual bluegrass before they sprout. Aim to apply pre-emergents when soil temperatures drop to around 70°F.

Spring Pre-Emergent Application: What You Need to Know

pre-emergent herbicides
Water pre-emergent treatments in well after application.

Spring is an essential time to apply pre-emergents, as warm-season weeds will quickly take over your lawn if left unchecked.

For best results, apply the herbicide evenly across your lawn and water it in to activate the chemical barrier. If you apply too late, the weeds will have already begun to sprout, and post-emergent treatments will be necessary.

Texas A&M Agrilife Extension (n.d.) Weed and feed products used for other purposes in the landscape may already contain preemergence herbicides. Application of separate preemergence herbicides in addition to these products may lead to over-application that can be harmful to your lawn.

North Texas Weeds Controlled by Pre-Emergents

Different weeds emerge in different seasons, so using a pre-emergent at the right time is crucial. Here’s a list of common North Texas weeds that are able to be managed with pre-emergents:

More Lawn Tips:  Say Goodbye to Grassburrs: Tips for a Burr-Free Lawn

Spring & Summer Weeds:

  • Crabgrass
  • Dallisgrass
  • Goosegrass
  • Spurge
  • Purslane
  • Sticker burs

Learn more about sticker bur removal.

Fall & Winter Weeds:

what are pre-emergents?
Henbit is a winter weed.
  • Henbit
  • Chickweed
  • Annual bluegrass (Poa annua)

Pre-Emergent Herbicide Fact List

  • Pre-emergents must be watered in to activate the barrier that prevents weed germination.
  • They don’t kill existing weeds—use post-emergent herbicides if weeds are already visible.
  • Application timing is critical—too early or too late reduces effectiveness.
  • Soil temperature matters—use a soil thermometer to ensure proper timing.
  • Different products target different weeds—check labels to choose the right pre-emergent for your lawn’s needs.
apply pre-emergent in spring
Use a pre-emergent herbicide to kill crabgrass.

Crabgrass

Crabgrass is one of the most persistent and troublesome weeds in North Texas lawns. It thrives in warm temperatures and quickly spreads, overtaking healthy turfgrass. Applying a pre-emergent herbicide in early spring, before soil temperatures reach 55°F, is the only way to prevent crabgrass seeds from germinating.

Once it takes root, crabgrass becomes much harder to control, requiring post-emergent treatments. Proper lawn care, including regular mowing and adequate watering, also help minimize crabgrass infestations by promoting thick, healthy grass.

DIY vs Professional Pre-Emergent Application

what are pre-emergents?
Get a lush, green lawn this spring with help from Ryno Lawn Care.
While DIY pre-emergent application is tempting, hiring a professional for the job yields better results. Professionals have the experience to accurately assess your lawn’s specific needs, select the right herbicide, and apply it at the optimal time for maximum effectiveness.
They also understand the nuances of local soil conditions and weather patterns, which significantly impact the success of pre-emergent treatments. Additionally, professionals use specialized equipment to achieve even coverage.
For long-lasting, effective weed control, a professional application will save you time, effort, and frustration in the long run. Contact Ryno Lawn Care today to schedule a weed control treatment for your lawn.

Final Thoughts

Applying pre-emergent herbicides at the right time in North Texas saves you from the headache of battling weeds all season long. Follow a proper application schedule and choose the right product and you will have healthy and beautiful lawn. If you need help with pre-emergent applications or lawn care, Ryno Lawn Care is here to assist!

FAQ about Pre-Emergent Herbicides

1. What is a pre-emergent herbicide?
A pre-emergent herbicide is a type of chemical treatment applied to soil before weed seeds have had the chance to germinate. It creates a barrier that prevents weed growth, making it an essential tool in maintaining a healthy, weed-free lawn or garden.

2. When should I apply pre-emergent herbicide?
Pre-emergent herbicides should be applied early in the growing season, typically in the spring or fall, depending on the type of weeds you’re targeting. For spring weeds, apply when soil temperatures reach about 55°F for several consecutive days. For fall weeds, aim for late summer to early fall before the weeds start germinating.

More Lawn Tips:  Lawn Weeds Identification Guide - Weeds in Texas

3. How do pre-emergent herbicides work?
Pre-emergent herbicides work by inhibiting the growth of weed seeds that are about to germinate. When applied correctly, they create a chemical barrier in the soil that prevents weed seeds from sprouting, effectively stopping their growth before they emerge.

4. Are pre-emergent herbicides safe for my plants?
Pre-emergent herbicides are generally safe for established plants when applied according to the manufacturer’s instructions. However, they will harm newly seeded lawns or certain sensitive plants. It’s essential to read labels carefully and avoid applying them to areas where you plan to plant seeds shortly after application.

5. Can I use pre-emergent herbicides on my vegetable garden?
Pre-emergent herbicides can be used in vegetable gardens, but it’s important to choose a product that is safe for edible plants. Some herbicides can interfere with seed germination, so make sure to select one labeled for use around vegetables and follow the recommended application guidelines.

6. How long do pre-emergent herbicides last?
The effectiveness of a pre-emergent herbicide typically lasts for 6 to 8 weeks, depending on the active ingredient, weather conditions, and soil type. You may need to reapply during the growing season for ongoing weed control.

7. Can pre-emergent herbicides control existing weeds?
Pre-emergent herbicides are designed to prevent weed germination, not to kill existing weeds. If you have mature weeds in your lawn or garden, they must be removed through mechanical means or post-emergent herbicides before applying a pre-emergent treatment.

8. How do I know which pre-emergent herbicide is right for my lawn?
The best pre-emergent herbicide for your lawn depends on the type of weeds you’re targeting. Some herbicides are more effective on grassy weeds, while others are better for broadleaf weeds. It’s also important to consider your local climate and soil type. Consulting with a lawn care professional can help you select the most suitable product for your needs.

9. Are there any environmentally friendly pre-emergent options?
Yes, there are organic and eco-friendly pre-emergent herbicides available that use natural ingredients such as corn gluten meal. These products can provide weed control without the use of harsh chemicals, but they require more frequent application and are less effective than synthetic alternatives.

10. Can I apply pre-emergent herbicide after it rains?
It’s best to apply pre-emergent herbicides when the soil is dry and allow for a light watering afterward to activate the product. Heavy rain shortly after application will wash away the chemical, reducing its effectiveness. Be sure to check the weather forecast and avoid applying just before a major storm.

References:

Texas A&M University Agrilife Extension. (n.d.) Preemergence herbicide guide. Texas A&M University. https://aggieturf.tamu.edu/wp-content/uploads/sites/24/Preemergence-Herbicide-Guide-4.pdf

University of Nevada. (n.d.). Using Pre-emergence herbicides for weed control in the home landscape. University of Nevada Extension. https://extension.unr.edu/publication.aspx?PubID=3172

 

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