Creating a beautiful, resilient lawn sometimes means considering a blend of grasses. Mixing bermuda grass with st augustine grass is a strategy some homeowners use, aiming to combine the strengths of both. Combining Bermuda grass with St. Augustine creates a mixed lawn that presents unique challenges for maintenance and growth. This article explains what happens when these two popular warm-season grasses share the same soil, and gives you practical advice for management.
You might be considering this mix to fill in bare spots, increase drought tolerance, or create a denser turf. Understanding the fundamental nature of each grass is the first step to knowing if this combination can work for you, or if it will become a constant battle in your yard.
Mixing Bermuda Grass With St Augustine Grass
The idea of a mixed lawn can be appealing. Bermuda grass offers toughness and drought resistance, while St. Augustine provides lush, shade-tolerant coverage. However, these grasses have very different growth habits and needs. Their natural competition often leads to one grass dominating over time, rather than a peaceful coexistence.
Before you decide to intentionally mix them, or if you’re trying to manage an existing blend, it’s crucial to know what you’re dealing with. Let’s break down the core characteristics of each grass type.
Understanding Bermuda Grass
Bermuda grass (Cynodon dactylon) is a fine-textured, aggressive warm-season grass. It thrives in full sun and is known for its exceptional drought tolerance and ability to withstand heavy foot traffic. It spreads primarily through runners called stolons, which grow above ground, and rhizomes, which grow below ground. This dual spreading mechanism makes it incredibly invasive.
- Growth Habit: Aggressive, spreads by stolons and rhizomes.
- Sunlight Needs: Requires full sun (6-8 hours minimum).
- Water Needs: Low to moderate; deep-rooted and drought-resistant.
- Mowing Height: Low (0.5 to 1.5 inches).
- Best For: High-traffic areas, sunny lawns, sports fields.
Understanding St. Augustine Grass
St. Augustine grass (Stenotaphrum secundatum) is a coarse-textured, fast-growing warm-season grass. It is prized for its dense, carpet-like appearance and good shade tolerance compared to other warm-season grasses. It spreads via above-ground stolons, which root at the nodes. It is less cold-tolerant and less drought-tolerant than Bermuda.
- Growth Habit: Fast-spreading via stout stolons.
- Sunlight Needs: Prefers full sun but tolerates moderate shade.
- Water Needs: Moderate to high; requires consistent moisture.
- Mowing Height: Higher (2.5 to 4 inches).
- Best For: Coastal areas, shaded lawns, where a lush look is preferred.
The Core Challenge: Competition And Invasion
The primary issue with mixing bermuda grass with st augustine grass is their incompatible growth strategies. Bermuda grass is simply more aggressive in most conditions. Given enough sunlight, its rhizomes will allow it to grow underneath and through a St. Augustine lawn, eventually choking it out.
St. Augustine, while fast-growing, cannot compete with Bermuda’s below-ground advance. In a mixed lawn, Bermuda often becomes a persistent weed within the St. Augustine, creating a patchy, uneven appearance. The different mowing height requirements also make proper care for one detrimental to the other.
Reasons People Mix These Grasses
Despite the challenges, homeowners often find themselves with a mixed lawn, either by accident or design. Understanding the intent can help you decide on your management path.
Intentional Mixing For Lawn Improvement
Some people intentionally sow Bermuda into thin St. Augustine to improve density, or use St. Augustine plugs to fill shaded areas in a Bermuda lawn. The goal is usually to leverage the strengths of each: Bermuda’s durability in sun and St. Augustine’s shade performance.
Unintentional Mixing Through Repair
This is very common. You might have a St. Augustine lawn and use a generic “sun and shade” grass seed or sod patch that contains Bermuda. Alternatively, Bermuda grass can invade from a neighbor’s yard or from contaminated topsoil. Before you know it, you have a mixed turf that’s hard to control.
Transition Zone Dilemmas
In areas where climates shift, a lawn might start as one grass type and slowly transition to another due to changing conditions, like increased shade from maturing trees or alterations in watering practices.
Practical Management of a Mixed Lawn
If you already have a mix of Bermuda and St. Augustine, you have three main options: manage the blend, eradicate one to favor the other, or completely renovate. Here is a step-by-step guide for each approach.
Option 1: Managing The Blend
This is the most difficult path and requires constant attention. The goal is not harmony, but controlled suppression of one grass to allow the other to be dominant.
- Identify Your Primary Grass: Decide which grass you want to be the main species in your lawn. Your local climate, sunlight, and personal preference will guide this.
- Adjust Mowing Height: If favoring St. Augustine, mow high (3-4 inches) to shade out Bermuda seedlings. If favoring Bermuda, mow low (1-1.5 inches), which will stress and thin the St. Augustine.
- Tailor Watering: For a St. Augustine-dominant lawn, water more frequently to keep soil moist. For Bermuda, water deeply but infrequently to encourage its deep roots and stress the St. Augustine.
- Fertilize Strategically: Both grasses need nitrogen, but timing can influence one over the other. Early spring feeding favors Bermuda’s early green-up. A consistent summer schedule supports St. Augustine.
- Manual Removal: Regularly dig out patches of the unwanted grass, ensuring you remove all stolons and rhizomes.
Option 2: Eradicating One Grass Type
This is a more definitive approach, choosing one grass to keep and selectively removing the other.
Removing Bermuda From St. Augustine
This is very challenging because non-selective herbicides will kill both grasses. Your best tool is a selective herbicide containing fenoxaprop. These products are often labeled for controlling grassy weeds (like Bermuda) in St. Augustine and Centipede lawns. Multiple applications over growing seasons are usually necessary, and it’s not always 100% effective.
- Apply the selective herbicide according to label directions, usually in early summer when both grasses are actively growing.
- Expect some yellowing or browning of the St. Augustine; this is normal.
- Repeat applications as directed, often 2-3 times per season.
- Reseed or re-sod the bare patches with St. Augustine after the herbicide’s waiting period.
Removing St. Augustine From Bermuda
This is slightly more straightforward because you can use non-selective herbicides like glyphosate on the St. Augustine patches without harming the Bermuda if applied carefully. Bermuda’s rhizomes often survive and regrow.
- Mow the lawn very short to expose the St. Augustine stolons.
- Use a sponge or wick applicator to paint glyphosate directly onto the St. Augustine foliage, avoiding the Bermuda as much as possible.
- After the St. Augustine dies, dethatch and remove the dead material.
- The existing Bermuda will quickly fill in the bare areas, especially if you fertilize lightly.
Option 3: Complete Lawn Renovation
When the mix is too extensive, starting fresh is often the most effective long-term solution. This involves completely killing the existing turf and planting a single, uniform grass type.
- Apply Non-Selective Herbicide: Use glyphosate to kill all existing vegetation. You may need two applications, 14 days apart.
- Remove Thatch and Debris: Once everything is dead, dethatch and remove the organic layer.
- Prepare the Soil: Test your soil, amend it based on results, and grade it smoothly.
- Install New Grass: Lay new sod or plant plugs of your chosen grass species (choose one, not both).
- Follow Establishment Care: Water diligently, hold off on fertilizer, and avoid traffic until the grass is rooted.
Key Considerations for Success
Sunlight Is The Deciding Factor
Sun exposure will ultimately determine which grass wins. In full sun, Bermuda will almost always dominate St. Augustine over time due to its aggressive rhizomes. In shaded areas, St. Augustine may hold its ground because Bermuda will thin and decline. Assess the sun patterns in your yard before making any plans.
Soil And Climate Conditions
Bermuda grass tolerates a wider pH range and poorer soil than St. Augustine. St. Augustine prefers slightly acidic to neutral soil and benefits from consistent organic matter. In areas with cold winters, Bermuda may go fully dormant (brown), while St. Augustine may retain some color but can be damaged by frost, leaving a mixed lawn looking inconsistent in the off-season.
Long-Term Maintenance Commitment
Choosing to manage a mixed lawn is not a one-time task. It is an ongoing commitment to cultural practices like mowing, watering, and manual weeding. Be honest with yourself about the amount of time and effort you are willing to dedicate to lawn care.
Frequently Asked Questions (FAQ)
Can You Mix Bermuda And St. Augustine Grass?
Technically, you can, but they will not coexist evenly. They are highly competitive, and one will typically invade and suppress the other. It is generally not recommended to intentionally plant them together for a uniform lawn.
Which Grass Will Win: Bermuda Or St. Augustine?
In full sun conditions with standard maintenance, Bermuda grass will almost always outcompete and choke out St. Augustine grass due to its aggressive below-ground rhizomes. In consistently shaded areas, St. Augustine may persist longer as Bermuda weakens.
How Do I Get Rid Of Bermuda In My St. Augustine Lawn?
You can use a selective herbicide labeled for grassy weed control in St. Augustine lawns, containing fenoxaprop. Multiple applications are needed. Manual removal of patches, including all roots and runners, is also necessary but labor-intensive.
What Is The Best Grass To Mix With St. Augustine?
St. Augustine is best grown alone. If you need to fill areas, use more St. Augustine. Mixing it with other grasses creates maintenance headaches. For shade, consider alternatives like certain dwarf varieties of St. Augustine itself.
Will Bermuda Grass Take Over St. Augustine?
Yes, if conditions are favorable (primarily full sun), Bermuda grass will gradually but steadily take over a St. Augustine lawn. Its rhizomes allow it to spread underneath the St. Augustine canopy, emerging and eventually crowding it out.
Managing a lawn with both Bermuda and St. Augustine requires a clear strategy and realistic expectations. By understanding the aggressive nature of Bermuda and the specific needs of St. Augustine, you can make informed decisions. Whether you choose to manage the blend, eradicate one type, or start over, consistency is your most important tool. Assess your lawn’s conditions, choose the grass that best suits your environment, and commit to the maintenance plan it requires for a healthy, attractive yard.