How To Get Rid Of St Augustine Grass In Bermudagrass
Do you find yourself staring at your lawn, frustrated by those thick, coarse patches of St. Augustine creeping into your fine-textured Bermuda? You aren’t alone, as many homeowners struggle when these two warm-season giants clash in the same yard. It can feel like an uphill battle to maintain that smooth, golf-course look when an invader takes hold.
The good news is that you can successfully tip the scales in favor of your preferred turf with the right strategy. In this guide, I will show you exactly how to get rid of st augustine grass in bermudagrass without destroying your entire lawn in the process. We will look at professional-grade chemical solutions, cultural shifts, and manual methods to ensure your Bermuda thrives.
By the end of this article, you will have a clear, step-by-step roadmap to eliminate the intruder and prevent it from ever coming back. Whether you are dealing with a few stray stolons or a massive takeover, these proven techniques will help you restore your lawn’s beauty. Let’s dive in and get your grass back on track!
What's On the Page
- 1 Understanding the Battle: Why St. Augustine Invades
- 2 how to get rid of st augustine grass in bermudagrass Using Selective Herbicides
- 3 The Power of Mowing: Using Cultural Controls
- 4 Manual Removal for Small Patches
- 5 Optimizing Soil Nutrition to Favor Bermuda
- 6 The Importance of Sunlight Management
- 7 Frequently Asked Questions About Removing St. Augustine
- 8 Conclusion: Stay Persistent for a Perfect Lawn
Understanding the Battle: Why St. Augustine Invades
Before we pick up a sprayer or a shovel, we need to understand our opponent. St. Augustine is a formidable grass because it spreads via stolons, which are thick, above-ground runners. These runners can quickly leap over garden edging and weave themselves into the dense mat of your Bermuda turf.
Bermuda, on the other hand, is much finer and spreads through both stolons and rhizomes (underground stems). While Bermuda is incredibly resilient, it requires full sun to stay competitive. If your lawn has shady spots, the St. Augustine will naturally gain the upper hand because it is far more shade-tolerant than its counterpart.
Identifying the exact areas where the encroachment is happening is the first step. Look for the wider, blunt-tipped leaf blades of the St. Augustine. Once you have mapped out the “infestation zones,” you can decide which of the following methods will work best for your specific situation.
how to get rid of st augustine grass in bermudagrass Using Selective Herbicides
The most effective way to handle a large-scale invasion is through the use of selective herbicides. Because both are warm-season grasses, you cannot just use a generic weed killer, or you risk killing your prized Bermuda as well. You need a product that exploits the physiological weaknesses of St. Augustine.
Many professional lawn care experts use products containing Quinclorac. While often marketed as a crabgrass killer, Quinclorac is notoriously tough on St. Augustine while being perfectly safe for established Bermuda. When applied correctly, it stunts the growth of the broader blades, eventually causing them to wither away while the Bermuda fills in the gaps.
Another option is to look for “Weed and Feed” products specifically labeled for Bermuda lawns that include a warning: “Do not use on St. Augustine grass.” This warning is actually your best friend in this scenario. It indicates that the chemical makeup is toxic to the very grass you are trying to remove. Always follow the label instructions to the letter to avoid stressing your lawn.
Safety Precautions for Chemical Application
When working with any herbicide, safety should be your top priority. Always wear long sleeves, pants, and chemical-resistant gloves. Ensure there is no wind to prevent “drift,” which could accidentally kill your ornamental flowers or your neighbor’s healthy St. Augustine lawn.
Check the weather forecast before you spray. Most selective herbicides need at least 24 to 48 hours of dry weather to be fully absorbed by the leaf blades. If it rains too soon, the chemical will wash away into the soil, potentially reaching the roots of plants you want to keep.
The Power of Mowing: Using Cultural Controls
One of the most “pro” tips I can give you is that you can actually mow St. Augustine into submission. These two grasses have very different height preferences. Bermuda loves to be kept short, usually between 1 and 1.5 inches. St. Augustine, however, thrives when it is 3 to 4 inches tall.
By dropping your mower blade to 1 inch, you are performing scalping on the St. Augustine. This removes its ability to photosynthesize effectively. Bermuda is much tougher and can handle this low height, whereas the St. Augustine will become stressed, weakened, and eventually die off because it cannot sustain its thick stolons with such little leaf surface.
Consistency is key here. You cannot just mow low once and expect results. You must maintain this low height throughout the peak growing season. This constant pressure favors the fine-textured Bermuda and makes the environment inhospitable for the broader-leafed invader.
Frequency Matters
When you are mowing low to suppress an invader, you need to mow more frequently. Aim for twice a week during the summer. This prevents the St. Augustine from recovering between cuts and keeps your Bermuda dense, which naturally chokes out any remaining unwanted sprigs.
Ensure your mower blades are razor-sharp. Ragged cuts from dull blades stress the grass and make it susceptible to disease. A clean cut helps the Bermuda recover quickly from the low height, allowing it to spread its rhizomes and reclaim the bare spots left behind by the dying St. Augustine.
Manual Removal for Small Patches
If you only have a few patches of unwanted grass, manual removal is often the fastest and most environmentally friendly route. Because St. Augustine spreads via surface stolons, it is actually quite easy to pull up by hand if the soil is moist. I recommend doing this after a light rain or a scheduled watering session.
Follow the long runners back to their source and gently lift them out of the Bermuda. Be careful not to leave small segments behind, as even a tiny piece of a stolon can sometimes take root again. Using a hand trowel or a specialized weeding tool can help you get under the “nodes” where the grass is anchored.
Once you have removed the physical grass, you will likely have a small bare spot. Don’t leave this empty! Bermuda is an aggressive grower, but you can help it along by adding a little topsoil and a high-nitrogen fertilizer to the area. This encourages the surrounding Bermuda to “sprint” into the open space before weeds can take hold.
Optimizing Soil Nutrition to Favor Bermuda
Bermuda is a “heavy feeder,” meaning it requires significant amounts of nitrogen to stay lush and competitive. St. Augustine also likes nutrients, but it doesn’t respond to high-nitrogen blasts in quite the same way. By timing your fertilization correctly, you can give your Bermuda the “fuel” it needs to outpace the competition.
Apply a high-quality, slow-release nitrogen fertilizer in late spring and again in mid-summer. This keeps the Bermuda in a state of rapid growth. When Bermuda is growing vigorously, its root system becomes incredibly dense, making it very difficult for the stolons of St. Augustine to find a place to anchor themselves.
It is also a great idea to perform a soil test. Bermuda prefers a slightly acidic to neutral pH (6.0 to 7.0). If your soil is too alkaline, the Bermuda may struggle to take up nutrients, giving the St. Augustine an opening to take over. Adjusting your pH with sulfur or lime can make a world of difference in lawn health.
The Importance of Sunlight Management
As I mentioned earlier, sunlight is the ultimate deciding factor in the war between these two grasses. If you are wondering how to get rid of st augustine grass in bermudagrass in a shaded area, the truth is that it might be nearly impossible. Bermuda requires at least 6 to 8 hours of direct, unfiltered sunlight to survive.
If you have overhanging tree branches, consider thinning the canopy. Increasing the light penetration to the ground level will instantly boost the health of your Bermuda. If the area remains shaded despite your best efforts, you might need to accept that Bermuda won’t grow there and consider a different ground cover or a mulch bed.
For areas that get plenty of sun, simply removing the shade competition is often enough to let the Bermuda naturally reclaim the territory. Once the light levels are high, the St. Augustine loses its primary advantage, and your cultural practices (like low mowing) will be much more effective.
Frequently Asked Questions About Removing St. Augustine
Will vinegar kill St. Augustine grass without hurting my Bermuda?
No, vinegar is a non-selective herbicide. This means it will kill or severely damage any green vegetation it touches, including your Bermuda. It is much better to use a selective herbicide like Quinclorac or stick to cultural methods like low mowing and high fertilization.
How long does it take for St. Augustine to die off?
If you are using the mowing and fertilization method, it can take an entire growing season to fully eradicate the invader. If you use selective herbicides, you will usually see the St. Augustine begin to yellow and wither within 7 to 14 days, though a second application may be necessary for stubborn patches.
Can I just overseed my Bermuda to drown out the St. Augustine?
Overseeding can help, but only if you are using common Bermuda seed. Most high-end lawns use hybrid Bermuda, which does not produce viable seeds and must be spread via sod or plugs. The best way to “drown it out” is to encourage the existing Bermuda to spread through proper feeding and low mowing.
Is it better to pull St. Augustine or spray it?
This depends on the size of the area. For small “volunteers” that have just jumped a flower bed border, pulling them by hand is best. For a lawn where the two grasses are heavily mixed, spraying with a selective herbicide is far more efficient and less back-breaking.
Conclusion: Stay Persistent for a Perfect Lawn
Learning how to get rid of st augustine grass in bermudagrass is a journey, not a one-time event. It requires a combination of the right chemicals, a disciplined mowing schedule, and a bit of patience. Remember, you are trying to shift the entire ecosystem of your yard to favor one species over another, and that takes time.
Don’t get discouraged if a few broad blades pop up after your first treatment. Just stay consistent with your 1-inch mowing height and keep that Bermuda well-fed with nitrogen. Before you know it, those coarse patches will be a thing of the past, replaced by a carpet of fine, beautiful Bermuda turf.
You’ve got this! With these expert tips in your gardening toolkit, your lawn will soon be the envy of the neighborhood. If you ever feel overwhelmed, just take it one patch at a time. Happy gardening, and enjoy your beautiful, uniform lawn!
