Bermuda Grass Invading Your St. Augustine: What Actually Works
Bermuda creeping into St. Augustine is one of the hardest lawn problems to fix. Here are your real options, from selective treatments to spot-killing and replugging.
The short version
- There's no quick, easy spray that removes Bermuda from St. Augustine without risk to the lawn.
- Selective options exist, but they take repeat applications and can stunt St. Augustine for a while.
- For patches, the most reliable fix is to spot-kill and replug.
- A thick, tall St. Augustine lawn is the best long-term defense.
How to spot Bermuda in St. Augustine
Bermuda has fine, narrow, pointed blades, while St. Augustine's are wide and flat with rounded tips. Bermuda spreads by both above-ground runners and underground rhizomes, so it pops up in patches and creeps in from beds and neighboring yards. It also thrives in full sun and greens up earlier in spring, which makes it easy to spot then. Not sure what you have? See St. Augustine vs. Bermuda.
Why it's so hard
Both are warm-season grasses that grow at the same time and respond to the same things. Most herbicides that kill one damage the other. Bermuda's underground rhizomes also let it regrow after the top is killed.
Option 1: Selective treatment (slow, takes repeats)
University of Georgia Extension lists one selective approach for St. Augustine: ethofumesate combined with atrazine. A few key points from their guidance:
- Start in spring as Bermuda greens up. Starting on actively growing Bermuda in summer usually fails.
- Expect to repeat about every 30 days, once the lawn recovers.
- St. Augustine often looks stunted or off-color for a while after each treatment.
- Atrazine alone slows Bermuda but doesn't get rid of it.
Follow product labels exactly, and check with your county extension office for current local recommendations.
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Option 2: Spot-kill and replug (most reliable for patches)
- Spray the Bermuda patch plus a small border around it with a non-selective herbicide like glyphosate. It kills St. Augustine too, so be precise and use a shield on windy days. Fall applications tend to work better than summer ones.
- Wait and re-treat any green regrowth from the rhizomes.
- Replant with St. Augustine plugs or sod after the label's waiting period. I cut and set plugs with a soil plug tool so each one sits level with the lawn. See how to plug bare spots.
Keep it from coming back
- Mow St. Augustine tall, at 3½ to 4 inches. Bermuda likes it short and struggles in shade. See mowing height.
- Edge beds and borders to stop runners creeping in from next door.
- Keep the lawn thick with steady feeding and deep watering. Bermuda moves into thin spots first.
Everything in my St. Augustine program
The fertilizers, weed killers, fungicides, and tools I actually use on my own lawn, with links to buy.