St. Augustine Grass | Growing, Maintaining, Weed Control

The wide, blue-green blades of St. Augustine grass (Stenotaphrum secundatum) may not be as “turfy” as some other varieties. But you’ll have a hard time finding another species that thrives in (sub) tropical climates as well as this one.

St. Augustine’s hardiness doesn’t end with temperature and moisture. This grass tolerates a range of growing conditions and requires minimal maintenance on the part of its growers. 

The easygoing nature of St. Augustine makes it an attractive choice for any warm-climate lawn. But to get the most out of this turf grass, however, you’ll still need to do a little bit of maintenance throughout the year. 

That’s why I’ve put together this guide on everything you need to know about St. Augustine grass including how to grow and maintain it for lush green results.

St Augustine Grass Overview

Your familiarity with St. Augustine grass likely has a lot to do with your location. This warm-season grass is incredibly popular in subtropical climates thanks to its tolerance for heat and humidity. In the United States, this grass grows best in zones 8 through 10. 

St. Augustine also holds up to salty air much better than other varieties, making it a prime choice for lawns along the coastline. 

Planting St Augustine Grass

Soil preparation is the best investment you can make in your new St. Augustine lawn. Whether you’re starting with an empty lot or replacing another type of grass, there’s literally no better time to loosen and amend the soil bed.

Even the professionals can’t tell what nutrients are or are not in native soil by instinct alone. Performing a soil test will remove the guesswork from supplementing nutrition, adjusting acidity, and more.

Soil pH Test For St Augustine Grass

St. Augustine grass tolerates a soil pH between 5.0 and 7.0. However, it grows best in slightly acidic soil with a pH between 6.0 and 6.5. Amending the soil’s pH is rarely necessary when planting St. Augustine.

When preparing for lawns or performing other high-cost activities in your yard, it’s a no-brainer to perform a high-quality soil test. When I say high-quality, what I mean is a Laboratory test and not a home test. You can pick up a Soil Test Kit from Amazon is similar for a relatively low price, and send a sample of your soil off to a professional test lab for analysis.

The Lab test results will provide you with a professional quality soil analysis, the breakdown of the nutrients, along with recommended actions to amend or improve your soil quality.

In cases when amending the soil pH is required, I recommend using a tried-and-true material like aluminum sulfate (to lower pH) or agricultural lime (to raise pH). 

St Augustine Grass Seed

You won’t find St. Augustine grass seed at your local garden center! This turf species can only be spread vegetatively (typically via sod or smaller plugs).

That’s not to say that St. Augustine grass does not produce seeds at all. It does. But it produces viable seeds at a rate that is not fit to collect and sell commercially.

How And When To Plant St Augustine Grass

As a warm-season turfgrass, St. Augustine does most of its growth during the peak of spring and summer. Planting this grass early on in the year will give it plenty of time to establish before winter. Allow at least 90 days before the first frost when installing new St. Augustine grass.

St Augustine Grass Sod

With sod, you can lay a full, lush lawn in as little as a day. The only true downside to installing St. Augustine sod is the cost. However, this type of planting still requires care and attention in the weeks following installation to be properly established.

Sod Early Care

Proper irrigation is crucial for healthy sod. Fresh sod is at risk of both over and underwater. New sod is vulnerable to drying out, particularly on hot days as the grass’s roots need time to grow and bond to the underlying soil bed.

I recommend preparing your soil bed with organic matter to loosen the substrate and allow it to retain moisture. Thoroughly soak the soil 24-48 hours before you plan to lay your new sod. This will allow water to penetrate deep into the soil, and also give you enough time to prevent a muddy mess when you start working.

After laying your sod, water early morning and water deep…do this whenever the sod soil begins to dry. Watch for yellow discoloration along the sod edges, which is a clear sign that the sod is dehydrated. If you see this you need to provide more water. The key is to thoroughly soak the ground and not just do small irrigation efforts often. But less frequent very heavy watering will reach deep into the sub-soil and encourage the sod roots deep into the soil to find their own moisture.

St Augustine Plugs

St. Augustine plugs are a more economical option than sod. If you’re unfamiliar with this method, plugs are essentially small segments of sod. Over time, the grass’s stolons will spread and fill the gaps between each plug, creating a dense carpet of grass.

You can install St. Augustine plugs yourself fairly easily using a digging tool called an auger. On average, plugs should be spaced every 12 to 18 inches. Keep the soil well-watered for the first few months allowing the grass roots to penetrate deep into the soil and become self-sufficient in maintaining their moisture requirement.

It can take several months for St. Augustine planted this way to completely cover the soil but you should see the plugs start to spread within 2 weeks. Maintain the grass during the first growing season as you would fresh sod.

Overseeding St Augustine Grass

Overseeding — spreading new seeds over an existing lawn — is one of the most effective ways to repair or rejuvenate a yard. Even if you don’t need to overseed right now, it’s a great strategy to keep in your lawn care arsenal for the future.

The lack of commercially available seeds seemingly makes overseeding thin or patchy St. Augustine turf. You can, however, oversee this grass using another species.

Alternatively, you can use St. Augustine plugs to repair bare sections of the lawn.

Best Grass To Mix With St Augustine

You’ll want to select another warm-season grass to mix with your St. Augustine turf. Bermuda grass is the most popular choice.

In warm climates, St. Augustine and Bermuda are quite compatible. You will, however, want to ensure your lawn receives enough sun for Bermuda grass to thrive. You will also need to mow more frequently than when caring for St. Augustine alone. 

How To Care For St Augustine Grass

St. Augustine grass earns much of its popularity from how easy it is to maintain. Routine irrigation and fertilization are all most lawns need to look their best throughout the growing season. This grass requires less frequent mowing than many other varieties. 

An established lawn will choke out most weeds. Just don’t skimp on maintenance like aeration and dethatching, which will keep St. Augustine’s naturally thick growth under control.

How Does St Augustine Grass Spread

Nearly all turfgrass spreads using special stems called rhizomes or stolons. Rhizomes grow below the ground. Stolons stay above the ground. St. Augustine grass spreads by the later, stolons. 

St. Augustine grass puts out stolons in all directions as it matures. These stolons then produce their own roots and leaves, becoming fully formed plants that can survive independently of the stolon. Healthy St. Augustine will spread indefinitely until the entire area is covered in a thick carpet. 

Encourage Thicker St Augustine Growth

If your St. Augustine grass is relatively young, it may just need more time to produce the thick lawn of your dreams. Sparsely planted plugs often take multiple growing seasons to reach their full potential.

For established lawns, taking steps to encourage thick growth is especially important with this species since you can’t easily overseed to fill bare or sparse sections.

Aerate The Soil

Compaction is a somewhat inevitable phenomenon where the soil is packed down by foot traffic, vehicles, or even things like falling rain. Compacted soil impacts root growth and the grass’s ability to reach oxygen, water, and nutrients. This often leads to the grass thinning out over time.

Aerating the soil every one to two years is the best way to alleviate some of this compaction so that your St. Augustine grass can access everything it needs. Aerate St. Augustine grass in late spring or early summer after the lawn has fully left dormancy.

You can rent or buy a simple core aerator that will handle most residential lawns. I don’t recommend using a spike aerator, as these tools can actually worsen compaction in many cases.

Dethatching St Augustine

Thatch is a natural layer of dead plant matter that builds up along the soil’s surface. While this layer decomposes over time, turfgrass tends to produce new thatch material faster than it can break down.

Dethatch your lawn when the current layer is greater than ½-inch thick. I recommend using a manual dethatching rake instead of a vertical mower. You’ll be much less likely to damage the grass itself with this tool.

Beware: removing too much thatch at once can cause St. Augustine grass to thin out even further. This occurs when the grass’s stolons are damaged or removed along with the dead thatch layer. It’s better to remove a small amount of thatch every year than to let the layer accumulate.

Irrigation

Like many other warm-season types of grass, St. Augustine prefers to dry out a bit between waterings. Wait long enough after irrigating so that the grass actually shows signs of drought. According to Texas A&M University, this normally means watering every 5 to 10 days.

When you water your St. Augustine lawn, the goal should be to saturate the top 6 inches of soil. This ensures that the entire root system is irrigated.

Fertilizing St Augustine Grass

For the best results, apply 2 to 4 pounds of nitrogen per 1,000 square feet (this should be spread over several applications). St. Augustine responds well to potassium fertilizers, especially in late summer and early Fall, but phosphorus should only be applied if there is a deficiency.

To make St. Augustine grass greener without overapplying nitrogen, I suggest incorporating chelated iron into your summer fertilizer routine.

The best fertilizer for St. Augustine can either be in a liquid or granular feed, depending on your preference. Most gardeners prefer granular formulas due to their convenience and affordability.

Mowing

St. Augustine grass performs best when kept relatively long — at least compared to many other warm-season types of grass. You should maintain St. Augustine grass between 2 and 2 ½ inches in the cooler months and between 2 ½ and 4 inches during the warmer months. 

According to the Clemson Cooperative Extension, grass growing in shaded areas should be kept between 3 and 4 inches. Also, maintaining a longer lawn during extreme heat or drought can help protect the grass as a whole.

Weed Control For St Augustine Grass

St. Augustine is generally categorized as weed-resistant grass. But this turf species can still be overrun by hardy weeds if they are allowed to flourish unchecked.

Promoting a thick, healthy lawn is the first step toward weed control. I still recommend having a diverse (and well-researched) arsenal at your disposal so you can eliminate more persistent weeds.

Fall Pre-Emergent

Pre-emergent herbicides — products that prevent weed seeds in the soil from germinating — are best applied in fall or winter. Be sure to identify the common weeds in your lawn and select a formula that will target them.

Using a pre-emergent herbicide for St. Augustine can be problematic when you plan to be overseeded in the spring. While St. Augustine is immune from such issues, keep this in mind if you plan to be overseeded with a different grass species. Allow several months between applying a pre-emergent weedkiller and spreading new grass seeds.

Summer Post-Emergent Herbicide

Once weeds are actively growing, using either a handheld weed-puller or a post-emergent herbicide is some of the best ways to get rid of them. 

St. Augustine grass is sensitive to 2,4-D, a common chemical in many post-emergent herbicides. Follow the mixing and application instructions carefully when using this chemical on your lawn. Do not apply the herbicide when the grass is dormant or suffering from summer heat stress.

Again, you should identify the weeds plaguing your property and select an appropriate formula. You should not blindly apply a random herbicide in hopes that it will kill the offending plants.

Weed And Feed For St Augustine Grass

Weed and feed is a mixture of fertilizer and herbicide that feeds grass and kills weeds in a single step. 

If you find your lawn is in need of weed control and fertilizing at the same time, applying weed and feed is very convenient. But I don’t recommend using it for routine feeding throughout the year.

Also, many weed and feed products contain 2,4-D and other herbicidal chemicals that can harm St. Augustine grass. Always check the labels of these products before applying them to your lawn.

St Augustine Lawn Care Through The Year

St. Augustine is rarely grown in areas with dramatic seasonal changes. That doesn’t change the fact that your lawn’s needs will change throughout the year. 

A maintenance routine that changes with the seasons is often the difference between a lush, green lawn and one that is just okay. 

How to Care for St Augustine | DoMyOwn.com

Spring Care

You may be eager to kick your lawn out of winter dormancy as soon as possible but jumping the gun on spring fertilization is a surefire way to damage St. Augustine grass! Take things slow and wait until all risk of frost is gone before encouraging rapid growth.

Weed Control

Pre-emergent herbicides should be applied in early spring to control weeds that emerge in late spring and throughout summer.

Although post-emergent herbicides can be used throughout the year to control weeds as needed, these products should not be used when St. Augustine grass is leaving winter dormancy. Once the grass starts to turn green, cease the use of post-emergent formulas until the grass is fully greened up.

Fertilizing

Spring fertilization should follow the guidance of a recent soil test to replenish necessary nutrients. Nitrogen-containing fertilizer is not recommended at this time because it puts the grass at risk of too much growth before the year’s final frost.

Mowing

St. Augustine grass should be kept relatively short in the spring. Mow to a height between 2 and 2 ½ inches just before the grass greens up.

Watering

Many areas receive enough rain throughout winter and spring to sustain warm-season grasses like St. Augustine. A good rule of thumb is to water St. Augustine grass if the area has not received rain for at least 3 weeks.

Summer Care

Summertime maintenance is a delicate balance between maximizing growth and protecting your lawn from heat and drought. Adopt good habits early on in the season — St. Augustine grass needs adequate nutrition now more than ever — so your lawn can weather the worst of what summer has to offer.

Weed Control

Summertime weed control should be kept to an absolute minimum. If you must treat summer weeds, proceed carefully. Never apply post-emergent herbicides to St. Augustine grass when it is under stress from heat or drought.

Personally, I recommend managing summer weeds by mowing or even hand-pulling. You can then plan ahead for next year by applying a pre-emergent herbicide in the fall or early spring.

Fertilizing

Summer St. Augustine fertilization is typically split into 2 to 3 applications. Divide your lawn’s required annual nitrogen — 2 to 4 pounds per 1,000 square feet is recommended — evenly between these applications.

Potassium can be applied throughout the summer months but is most important in mid-and late summer. Phosphorus should only be applied if a soil test shows a deficiency.

Mowing

St. Augustine grows best when it is kept quite tall. During the summer, your lawn should be maintained between 2 ½ and 4 inches tall. 

Watering

St. Augustine grass should be watered when it shows signs of moisture stress. This is typical of most warm-season turf species.

Always water deeply to saturate the top several inches of soil. Approximately 1 inch of water per session is enough for most lawns. 

Pest Control

Chemical insecticides tend to be the most effective strategy against common St. Augustine pests. Monitor the grass for signs of damage — the earlier you identify an infestation, the better chance your lawn has of recovery.

Mole crickets are a notable exception to this approach. These pests are easier to control before they reach adulthood. If your lawn is prone to mole cricket damage, apply a preventative insecticide in mid-summer to kill off any nymphs.

Fall Care

Summer and fall maintenance of St. Augustine grass is extremely similar. However, you’ll need to make a few simple changes to your mowing and fertilizing routines to prepare for winter.

Remember: your lawn doesn’t care about the calendar. Average temperatures determine when St. Augustine grass will wind down for the year and enter dormancy.

Weed Control

According to Texas A&M University, a pre-emergent herbicide designed for winter weed control can be applied once the soil temperature drops to 70°F.

You can also use post-emergent herbicides at this time to control weeds that are actively growing. Be sure to follow the manufacturer’s guidelines for use on St. Augustine grass (especially if the product contains ingredients like 2,4-D).

Fertilizing

Do not apply nitrogen in the fall. Nitrogen will encourage St. Augustine grass to grow, which is the opposite of what you want leading up to cooling temperatures and winter dormancy.

Fertilizers containing potassium can still be used at this time. Ideally, this should be applied 1 to 2 months before your area’s first frost date.

Mowing

Continue your summer mowing routine until the nightly temperatures drop to 70°F or below. You can then raise your mower blade’s height up to 1 inch. Allowing the grass to grow a bit taller will protect the roots from impending frost.

Watering

Prevent drought stress by watering as needed until the St. Augustine grass goes dormant. The frequency will ultimately depend on how much rain your lawn receives during the season.

Winter Care

Your St. Augustine lawn may not collect a blanket of winter snow. But it’s still important to give the grass a break. Care should be minimal and focus on maintaining the lawn’s health through dormancy. 

Mowing

Cease mowing as soon as St. Augustine grass shows signs of winter dormancy. 

If you live somewhere warm enough that your lawn does not enter dormancy, you can continue mowing throughout winter as needed. Just keep in mind that this scenario is rare, and mowing St. Augustine that has gone dormant can damage the plant!

Weed Control

Areas where St. Augustine is most commonly grown rarely see low enough temperatures to prevent all weeds. Once the grass enters dormancy, you can safely apply a post-emergent herbicide to kill off persistent winter weeds.

St Augustine Grass Problems

Nearly all of St. Augustine’s problems are caused by fungi. The most common fungal diseases seen in this grass species include:

• Brown Spot (caused by Rhizoctonia solani)
• Take-All Root Rot (caused by Gaeumannomyces graminis var. graminis)
• Fairy Rings (caused by various fungi)
• Stolon Rot (caused by Nigrospora sphaerica)

Some varieties of St. Augustine may be more susceptible to these diseases than others. I recommend talking to a local lawn care expert to determine which diseases are most common in your area.

Unfortunately, we can’t discuss the weaknesses of St. Augustine grass without also bringing up chinch bugs. The most common signs of infestation are irregular, rapidly expanding brown patches. Chinch bugs feed on a variety of grass species but only cause serious damage to St. Augustine.

The best treatment for these diseases is prevention. Ensuring your St. Augustine grass receives proper nutrition and sufficient watering throughout the entire year will make it less vulnerable to fungi and pests. Chinch bugs can also be managed by routinely removing excess thatch and when preventative measures fall short, chemical insecticide.