Overseeding St. Augustine With Bermuda: What You Need To Know

Bermuda grass and St. Augustine grow in similar climates: warm regions with heavy precipitation. However, St. Augustine lawns can fail for many reasons—drought, disease, heavy traffic, or excessive heat. In these cases, Bermuda grass may be a better option for your yard.

First, perform a test to see if Bermuda grass performs well in your lawn. You can do this by observing your current lawn conditions, or by overseeding a small area with Bermuda seed.

If Bermuda grows better in your lawn than St. Augustine, you can proceed with overseeding. Keep in mind, Bermuda will rarely overtake St. Augustine through overseeding alone. You will likely have to get rid of the St. Augustine before seeding with Bermuda, unless you want a mixed-grass yard.

Overseeding St. Augustine with Bermuda

How to Tell if You Should Overseed Your St. Augustine with Bermuda

To see if overseeding St. Augustine with Bermuda is a viable option, first determine the following.

  • Is invasive Bermuda already growing in your lawn?
  • Does your lawn receive midday sun?
  • Does a small area seeded with Bermuda grass perform well?

If the answer to one or more of these is yes, there’s a good chance Bermuda grass will perform well in your lawn, and may possibly even choke out weeds naturally.

Many St. Augustine lawns in the southeast perform poorly due to local soil conditions, while Bermuda naturally grows much more easily. If you’ve practiced proper St. Augustine grass care in your mowing, watering, and fertilization habits but your lawn is still failing, Bermuda could be the answer.

Signs of a Bermuda-Friendly Yard

Invasive Bermuda: A sure sign that your yard is viable Bermuda Lawn territory is if invasive Bermuda Grass has already taken hold. Many homeowners see Bermuda as a pest, but you may choose to embrace it.

Adequate Sunlight: Bermuda grass does not tolerate shade and will not grow in shady areas. If significant portions of your lawn are shaded throughout the day, Bermuda is not a good choice. If your lawn receives heavy midday sun, then it’s prime Bermuda territory.

Bermuda Grows where St. Augustine has Failed: Test a bare patch of yard, or remove a 3-foot-square section of St. Augustine. Seed Bermuda grass there and water it as you would a newly seeded yard. If Bermuda grass comes up and grows well, then odds are it is a good choice for your yard.

How to Overseed St. Augustine with Bermuda

If your lawn is already a Bermuda haven, receives good sunlight, and/or an overseeding test goes well, you can proceed with overseeding. Keep in mind, you won’t get good results by tossing out some seeds and hoping for the best. Existing St. Augustine will stop Bermuda from sprouting. If you want to transform a St. Augustine lawn into a pure Bermuda grass lawn, follow these steps:

Remove the St. Augustine

Remove the existing St. Augustine sod with a sod cutter. This will remove the grass, thatch layer, and roots all in one step, creating a clean slate for overseeding with Bermuda.

Some suggest using a glyphosate-based weed killer to kill St. Augustine grass instead, but this process involves the use of chemicals AND leaves you with the hard work of removing all that dead grass afterward. Bermuda grass will struggle to grow on a spongy bed of dead St. Augustine. Save yourself time and money by removing all the grass with a sod cutter.

Overseed with Bermuda

Once the St. Augustine grass is gone and the ground is prepared for overseeding, cast your Bermuda grass seed according to the volume specifications on the packaging. Then, water and care for the new seed diligently to prevent future weeds and promote healthy growth. For best results, overseed Bermuda grass in late spring, so it can establish itself over the summer growing period.

Can You Overseed St. Augustine with Bermuda Without Killing St. Augustine First?

It can be possible for some Bermuda grass to take root among St. Augustine. This depends on the yard though. For best results seeding Bermuda among existing St. Augustine, do the following:

Scalp Your Lawn

Mow your St. Augustine down to a height of 0.5 inches. By scalping your lawn, you increase the chance of adequate sunlight reaching Bermuda seedlings. If you don’t scalp your lawn first, the existing St. Augustine will stop your Bermuda seed from growing.

Overseed with Bermuda

Cast Bermuda seed over the scalped St. Augustine as you would on a bare lawn. Overseed in spring and follow a watering, fertilization, and care plan for new Bermuda seed. Since the seedlings have to battle with St. Augustine, they need all the help they can get.

Continue to Mow Low

Although they are both warm-season grasses, St. Augustine and Bermuda have different growing patterns. St. Augustine performs best when mowed at 3–3.5 inches in height, while Bermuda is a low-growing grass type that should be mowed at 1.5–2 inches in height. As your Bermuda grows in, continue to mow your yard at 1.5 inches, to give the Bermuda grass adequate sunlight.

Can You Mix Bermuda Grass with St. Augustine?

By scalping your St. Augustine and overseeding with Bermuda, you may be able to mix St. Augustine and Bermuda in your yard. However, unlike overseeding a warm-season grass with a cool-season grass in fall, don’t expect an even mix.

Bermuda is likely to take over sunny patches of your yard, where the heat can kill off St. Augustine. Meanwhile, St. Augustine may remain strong in shady parts of your lawn. The result can be a yard with islands of darker green Bermuda grass surrounded by bright green St. Augustine.

Will Bermuda Grass Take Over St Augustine?

Bermuda Grass is considered an invasive grass type in many areas for a reason—it can take over portions of a St. Augustine yard. This is due to the fact that Bermuda spreads through two methods: sprawling root systems (rhizomes) and invasive runners (stolons). In comparison, St. Augustine only spreads through aboveground stolons.

Under ideal circumstances, a St. Augustine lawn overseeded with Bermuda and mowed at 1.5 inches will encourage Bermuda to spread and choke out the St. Augustine. To ensure this, mow frequently to keep St. Augustine low. Additionally, it’s a good idea to jumpstart Bermuda growth with monthly fertilization through the peak summer months.

Getting Bermuda grass to take over St. Augustine can be a long, tough chore. For best results, remove existing St. Augustine before overseeding with Bermuda.

Should You Overseed St. Augustine with Bermuda?

If your St. Augustine lawn is failing, or is infected with brown patches or chinch bugs, it can be tempting to overseed with Bermuda grass. Before doing so, make sure Bermuda grows well in your lawn and that light conditions are optimal for Bermuda grass.

To turn a struggling St. Augustine lawn into a green lawn with thriving Bermuda, your best bet is to use a sod cutter to remove all existing St. Augustine grass before overseeding with Bermuda.

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