Herbicide For Dallisgrass – Reclaiming Your Lawn From This Pesky Weed

Is your once-pristine lawn now dotted with unsightly, coarse clumps of grass that just won’t go away? You’re likely battling dallisgrass, a tenacious perennial weed that can be a real headache for even the most dedicated homeowners and lawn enthusiasts. Its aggressive growth habit and deep root system make it particularly challenging to eradicate.

Many gardeners find themselves at a loss, trying various methods only to see dallisgrass return with a vengeance. But don’t despair! With the right knowledge and tools, you can effectively manage and significantly reduce its presence. This comprehensive guide will walk you through everything you need to know about using a targeted herbicide for dallisgrass, alongside best practices for long-term control.

We’ll cover identification, optimal timing, application techniques, and crucial safety measures. By the end, you’ll be equipped with the expertise to transform your lawn back into the lush, uniform carpet you’ve always desired, without the frustration of this stubborn invader. Let’s get started on reclaiming your green space!

Understanding Dallisgrass: The Enemy Within

Before we tackle the solution, it’s vital to understand the problem. Dallisgrass (Paspalum dilatatum) is a warm-season perennial grass native to South America. It thrives in moist, fertile soils and spreads aggressively.

You’ll recognize dallisgrass by its coarse, light-green blades that grow in distinct clumps. Its seed heads are characteristic, featuring 3-7 spike-like racemes along a central stem, each with two rows of hairy, flat seeds.

Unlike many annual weeds, dallisgrass is a perennial. This means it comes back year after year from its established root system, making it much harder to control. A single plant can produce thousands of seeds, further contributing to its spread.

Its clumping growth habit disrupts the uniform texture of desired turfgrasses. This creates an uneven appearance and can even outcompete desirable lawn species over time. Effective management requires a persistent, multi-faceted approach.

Choosing the Right Herbicide for Dallisgrass: Pre- vs. Post-Emergent

When selecting an herbicide for dallisgrass, understanding the difference between pre-emergent and post-emergent products is key. Each type serves a different purpose and is applied at a specific time.

Pre-Emergent Herbicides: Prevention Is Key

Pre-emergent herbicides create a chemical barrier in the soil that prevents seeds from germinating. They are a powerful tool for preventing new dallisgrass plants from emerging.

These should be applied in late winter to early spring, typically when soil temperatures consistently reach 50-55°F (10-13°C). This timing targets dallisgrass seeds before they have a chance to sprout.

Common active ingredients include prodiamine, pendimethalin, and dithiopyr. Always check the product label to ensure it’s safe for your specific turfgrass type. For instance, some pre-emergents can harm newly seeded lawns.

Remember, pre-emergents will not control existing dallisgrass plants. They are solely for preventing new weed growth from seed.

Post-Emergent Herbicides: Tackling Existing Weeds

Once dallisgrass has emerged and is actively growing, you’ll need a post-emergent herbicide. These products are designed to kill existing weeds.

For warm-season turfgrasses like Bermuda, Zoysia, and St. Augustine, products containing MSMA (monosodium methylarsonate) have historically been very effective. However, MSMA is restricted in many areas and for certain uses, so always check local regulations and product labels carefully.

Another effective option, particularly for cool-season grasses (though also used on some warm-season types), is quinclorac. This active ingredient is found in many selective herbicides and targets dallisgrass along with other grassy weeds.

Always ensure the herbicide is labeled as “selective,” meaning it will kill the dallisgrass without harming your desirable lawn grass. Non-selective herbicides, like glyphosate, will kill everything they touch, including your lawn.

Some products combine active ingredients for broader spectrum control. Carefully read the label to confirm the product is suitable for dallisgrass and your specific lawn type.

Application Strategies for Effective Dallisgrass Control

Proper application is just as important as choosing the right herbicide. Incorrect application can lead to poor results, damage to your lawn, or environmental contamination.

Timing Is Everything

For post-emergent herbicides, apply when dallisgrass is actively growing and healthy. This typically means late spring through early fall, when temperatures are between 65-85°F (18-29°C). Avoid application during drought stress or extreme heat.

Younger dallisgrass plants are generally easier to control than mature ones. Multiple applications, spaced according to label directions, are often necessary for complete eradication.

Pre-emergent herbicides, as mentioned, are applied in late winter to early spring before soil temperatures consistently reach 50-55°F. A second application in mid-summer can help control late-season germination.

Mixing and Equipment

Always follow the herbicide label for mixing ratios and application rates. Using too much can damage your lawn, while too little will be ineffective. Measure accurately.

Use a calibrated sprayer for even application. A pump sprayer is suitable for spot treatments, while a broadcast spreader or backpack sprayer is better for larger areas.

Clean your sprayer thoroughly after each use to prevent contamination. Dedicate a sprayer solely for herbicides if possible, to avoid accidental damage to desired plants.

Techniques for Success

For spot treatments, spray the dallisgrass clump until it is wet, but not dripping. Over-application can lead to runoff and damage to nearby plants.

When broadcasting, ensure even coverage. Overlapping passes slightly can help achieve this. Walk at a consistent pace.

Consider adding a non-ionic surfactant (NIS) if recommended by the herbicide label. Surfactants help the herbicide stick to and penetrate the waxy leaf surface of the dallisgrass, increasing efficacy.

Beyond Herbicides: Integrated Management for a Healthy Lawn

While a good herbicide for dallisgrass is a powerful tool, it’s only one part of a comprehensive strategy. Integrated Pest Management (IPM) combines cultural practices with chemical control for the best long-term results.

Proper Mowing Practices

Mow your lawn at the highest recommended height for your turfgrass type. Taller grass shades the soil, making it less hospitable for dallisgrass seeds to germinate. This also promotes a denser, healthier lawn that can outcompete weeds.

Regular mowing also helps to remove dallisgrass seed heads before they mature and spread. Bag clippings when dallisgrass is seeding to prevent further dispersal.

Optimal Watering and Fertilization

Deep, infrequent watering encourages deeper root growth in your desirable turfgrass, making it more resilient. Dallisgrass thrives in consistently moist conditions, so avoid overwatering.

Follow a balanced fertilization program based on soil test results. Healthy, vigorous turf is your best defense against weed invasion. An NPK ratio tailored to your grass type will encourage strong growth.

Avoid excessive nitrogen applications, which can sometimes favor weed growth over desirable turf in certain conditions.

Addressing Soil Health and Drainage

Dallisgrass often thrives in compacted soils with poor drainage. Aeration can improve soil structure, allowing water and nutrients to penetrate more effectively. This benefits your lawn while making the environment less favorable for dallisgrass.

Ensure proper surface drainage to prevent standing water, which dallisgrass loves. Correcting low spots or improving soil percolation can make a significant difference.

Manual Removal and Prevention

For a few scattered dallisgrass clumps, manual removal can be effective. Digging them out, ensuring you get the entire root system, prevents regrowth. This is easiest when the soil is moist.

Be diligent about removing dallisgrass before it sets seed. Early intervention saves a lot of work down the line.

Consider planting a dense, competitive turfgrass variety that can outcompete weeds. Some cultivars are naturally more aggressive and resilient.

Seasonal Timing and Ongoing Vigilance

Effective dallisgrass control is not a one-time event; it’s an ongoing process that requires seasonal attention.

Spring Strategy

Apply pre-emergent herbicides in early spring to prevent new dallisgrass germination. This is a critical step in breaking the weed’s life cycle.

Monitor your lawn for any existing dallisgrass clumps that survived the winter. As temperatures rise and dallisgrass begins active growth, apply post-emergent treatments as needed.

Summer Management

Continue to monitor for new dallisgrass emergence, especially after rainfall or irrigation. Summer is prime growing season for this weed.

Spot treat new dallisgrass clumps with a selective post-emergent herbicide. Remember to follow label instructions for reapplication intervals.

Maintain good cultural practices: mow high, water deeply, and avoid scalping your lawn.

Fall and Winter Prep

In late fall, as dallisgrass growth slows, it’s an excellent time for a final post-emergent application. The plant is often translocating nutrients to its roots for winter storage, which can help draw the herbicide deeper into the root system.

Continue good cultural practices into the cooler months. Prepare your lawn for winter dormancy, which will help it emerge strong in the spring.

Even in winter, identify and mark areas where dallisgrass was prevalent. This helps plan your spring pre-emergent strategy.

Safety First: Protecting Yourself, Your Lawn, and the Environment

Working with herbicides requires careful attention to safety. Always prioritize protecting yourself, your family, pets, and the environment.

Personal Protective Equipment (PPE)

Always wear appropriate PPE as directed by the product label. This typically includes:

• Long-sleeved shirt and long pants
• Chemical-resistant gloves (e.g., nitrile or neoprene)
• Eye protection (safety glasses or goggles)
• Closed-toe shoes or boots

Consider a respirator if working in enclosed spaces or if the product label recommends it.

Application Precautions

Apply herbicides on calm days to prevent drift onto desirable plants, water sources, or neighboring properties. Avoid windy conditions.

Keep children and pets off treated areas until the spray has dried completely, or for the duration specified on the product label. This can range from a few hours to 24 hours.

Do not apply herbicides near edible gardens or water features unless the product is specifically labeled as safe for such proximity.

Storage and Disposal

Store herbicides in their original containers, out of reach of children and pets, in a cool, dry, well-ventilated area. Never transfer herbicides to unlabeled containers.

Dispose of empty containers and leftover product according to local regulations and product label instructions. Do not pour down drains or into storm sewers.

Rinse application equipment thoroughly, disposing of rinse water in a manner consistent with label instructions. Never rinse equipment where runoff can contaminate water sources.

Troubleshooting Common Dallisgrass Control Issues

Even with the best intentions, controlling dallisgrass can sometimes be frustrating. Here are some common issues and their solutions.

Herbicide Didn’t Work

If your chosen herbicide for dallisgrass seemed ineffective, consider these factors:

• Wrong Timing: Was the dallisgrass actively growing? Post-emergents are less effective on dormant or stressed plants.
• Incorrect Application Rate: Did you measure accurately? Too little product won’t work.
• Product Compatibility: Was the herbicide specifically labeled for dallisgrass and your turf type?
• Resistance: While rare, some weeds can develop resistance over time. Try rotating active ingredients.
• Environmental Conditions: Extreme heat, drought, or recent rainfall can reduce efficacy.

Dallisgrass Keeps Coming Back

This is a common complaint due to its perennial nature and prolific seeding.

• Incomplete Root Kill: If only the top growth died, the roots will regrow. Multiple applications or stronger products may be needed.
• New Seed Germination: Are you using a pre-emergent? Without it, new seeds will constantly sprout.
• Seed Spread: Are you bagging clippings? Is dallisgrass from a neighbor’s yard spreading? Address these external factors.
• Unfavorable Lawn Conditions: Weak, thin turf provides open space for weeds to colonize. Improve soil health and turf density.

Damage to Desirable Lawn Grass

This usually occurs due to:

• Non-Selective Herbicide Use: Ensure you’re using a selective product.
• Over-Application: Too much product, even selective ones, can stress or kill your lawn.
• Wrong Turf Type: Some selective herbicides are safe for certain grasses but damaging to others (e.g., MSMA on St. Augustinegrass). Always check the label.
• Application During Stress: Applying herbicides to drought-stressed or heat-stressed lawns increases the risk of damage.

Frequently Asked Questions About Dallisgrass Control

Q1: Is There a Natural or Organic Herbicide for Dallisgrass?

A1: Controlling dallisgrass organically is very challenging. Vinegar-based products or horticultural soaps are non-selective and will damage desirable grass. Manual removal is the most effective organic method, but it’s labor-intensive for widespread infestations. Healthy lawn practices are crucial for prevention.

Q2: How Long Does It Take for Dallisgrass to Die After Herbicide Application?

A2: The time frame varies depending on the active ingredient, application rate, and environmental conditions. You typically start seeing signs of wilting and yellowing within 7-14 days. Complete death can take 2-4 weeks, and often multiple applications are necessary for full eradication.

Q3: Can I Overseed My Lawn After Applying a Dallisgrass Herbicide?

A3: It depends on the herbicide. Pre-emergent herbicides will prevent all seeds (including your desired grass seeds) from germinating for several weeks or months. Some post-emergent herbicides also have reseeding restrictions. Always check the product label for specific waiting periods before overseeding or sodding.

Q4: What’s the Best Time of Year to Apply a Pre-Emergent for Dallisgrass?

A4: Apply pre-emergent herbicides in late winter to early spring, typically when soil temperatures are consistently above 50-55°F (10-13°C) for several days. This usually corresponds to the time when forsythia bushes are blooming or before crabgrass starts to emerge in your area.

Q5: Will Glyphosate Kill Dallisgrass?

A5: Yes, glyphosate (a non-selective herbicide) will kill dallisgrass. However, it will also kill any other plant it touches, including your desirable lawn grass. It’s best used for spot treatments in areas where you don’t mind killing everything, or for preparing a bed for new planting. Be extremely careful with its application in a lawn setting.

Conclusion: Your Path to a Pristine Lawn

Tackling dallisgrass requires patience, persistence, and a strategic approach. By understanding this resilient weed and employing a combination of cultural practices and targeted herbicide use, you can effectively reclaim your lawn. Remember that choosing the right herbicide for dallisgrass is just one piece of the puzzle.

From timely pre-emergent applications to careful post-emergent treatments and consistent good lawn care, every step contributes to success. Always prioritize safety, read product labels thoroughly, and don’t be afraid to perform multiple treatments for stubborn infestations. With diligence and the expert guidance provided here, you’re well on your way to enjoying a beautiful, dallisgrass-free lawn once again. Happy gardening!

Taylor Galla Founder of Garden Aider

• Mechanical engineer
• Gardening since 2010
• Univ. of Nevada, Reno

From the author's notebook

Taylor pairs an engineer's eye with years of hands-on work in soil, lawns and outdoor machinery. He tests ideas in his own garden, keeps tractors and mowers running himself, and speaks to local horticulture groups. Every Garden Aider guide is written to be practical, accurate and safe to follow.

“To bring life alive, you just need to mix some love with the compost, bedding, and gardening machines.”

Published Jul 14, 2026 · Updated Oct 14, 2026