5 Best Fertilizers for St. Augustinegrass in 2022 [Reviews]

Lawn fertilizer being spread with a manual fertilizer spreader

St. Augustinegrass makes an attractive and tolerant lawn, but it needs proper maintenance to look its best. Part of that maintenance is choosing the right fertilizer and applying it at the right time. For a healthy, green lawn, peruse our top picks for the best fertilizers for St. Augustinegrass, then see our buyers guide for the best times to apply them. 

Top 5 Fertilizers for St. Augustinegrass – Reviews 

  • Some products listed are available on Home Depot and Lowe’s websites, which is noted below.

1. Pennington UltraGreen Lawn Fertilizer 

Pennington 100536576 UltraGreen Lawn Fertilizer, 14 LBS, Covers 5000 Sq Ft

Pennington’s lawn fertilizer is called UltraGreen for a reason: Its high nitrogen content and 5% iron will turn your lawn a deep green color in about a month or less. In addition to the quick green-up, your lawn will get continuous feeding for months because the fertilizer is partially slow-release nitrogen. 

UltraGreen is perfect for St. Augustine lawns in the South because it helps the grass survive extreme heat and drought conditions. It’s best for feedings in late spring and summer.

Specifications:

  • Type: Granular fertilizer 
  • NPK ratio: 30-0-4
  • Time release: Immediate-release and slow-release
  • Effective period: 12 weeks 
  • Package size: 14 lbs 
  • Coverage area: 5,000 square feet 
ProsCons
Fast-acting nitrogen for immediate green-up plus slow-release nitrogen for long-lasting effects

Phosphorus-free to prevent pollution in stormwater runoffAffordable
Nitrogen-rich blend will burn the grass and turn it brown if you over-fertilize

Not suitable for soils with a phosphorus deficiency 

Where to buy:

2. Milorganite 0636 Nitrogen Fertilizer

Milorganite 32 lb. Slow-Release Nitrogen Fertilizer

Milorganite’s nitrogen fertilizer is an eco-friendly option made of recycled nutrients. Unlike synthetic fertilizers, the organic matter in this fertilizer improves soil structure and benefits the microorganisms (such as bacteria and earthworms) that help with healthy grass growth. 

Another great thing about this fertilizer is that it isn’t very expensive, especially compared to other organic fertilizers. Plus, it’s an “all-purpose” formula, which means you can use it for plants in your garden in addition to your St. Augustinegrass. 

Specifications:

  • Type: Granular fertilizer
  • NPK ratio: 6-4-0
  • Time release: Slow-release
  • Effective period: 10 weeks 
  • Package size: 32 lbs
  • Coverage area: 2,500 square feet 
ProsCons
Made with organic, environmentally friendly material

Long-lasting results 

Affordable
Not for use in states with a ban on phosphorus fertilizers 

Doesn’t contain potassium 

Not listed by the Organic Materials Research Institute (OMRI) as approved for organic gardening 

Where to buy:

3. Scotts Turf Builder Southern Lawn Food

The Andersons Professional PGF Complete 16-4-8 Fertilizer with Humic DG 5,000 sq.ft.

Scotts Turf Builder Southern Lawn Food is designed specifically for lawns in the South that have to endure high temperatures and sometimes extended periods of drought during summer. The formula encourages your grass to develop stronger, deeper roots, which make the grass more tolerant of harsh conditions. 

With a high percentage of slow-release nitrogen, this fertilizer also helps your grass grow thicker, faster, and greener. Scotts patented All-in-One Particles distribute the nitrogen and other nutrients evenly to help prevent burning the grass, which is common with high-nitrogen fertilizers. 

Specifications:

  • Type: Granular fertilizer 
  • NPK ratio: 32-0-10
  • Time release: Slow-release 
  • Effective period: 6 weeks
  • Package size: 14 lbs
  • Coverage area: 5,000 square feet 
ProsCons
Perfect for warm-season grass types like St. Augustine 

Safe around pets and kids, even immediately after application

Phosphorus-free
Easy to damage the lawn if you over-fertilize in spots 

Doesn’t last very long compared to other slow-release fertilizers 

Not a good choice if your soil lacks phosphorus 

Where to buy:

4. The Andersons PGF Complete Fertilizer with Humic DG

The Andersons Professional PGF Complete 16-4-8 Fertilizer with Humic DG 5,000 sq.ft.

This fertilizer from The Andersons is considered “complete” because it contains the three most important plant nutrients, nitrogen, phosphorus, and potassium. It’s also considered “balanced” because the ratio of those nutrients is close to the ideal blend for all-around lawn health (the ideal is 3-1-2, and this fertilizer is 4-1-2).

While PGF Complete provides all the nutrients your St. Augustinegrass needs to grow healthier and thicker, it also helps grassroots absorb those nutrients better with the addition of Humic DG. Humic DG is a combination of humic acid and fulvic acid, organic elements that improve the roots’ nutrient uptake and increase the number of beneficial microorganisms in the soil.

Specifications:

  • Type: Granular fertilizer 
  • NPK ratio: 16-4-8
  • Time release: Slow-release
  • Effective period: 8 weeks
  • Package size: 18 lbs
  • Coverage area: 5,000 square feet
ProsCons
Complete and balanced for a wide range of soils 

Improves soil and plant health with humic acid 

Fine particle structure of the granules makes less product go further 
Expensive 

Not for use in states that ban phosphorus fertilizers

May take a while to see green-up (up to a month after application)

Where to buy:

5. BioAdvanced 3-in-1 Weed and Feed for Southern Lawns

BIOADVANCED 704840B 3 in 1 Weed and Feed for Southern 5M Lawn Fertilizer with Herbicide, 12.5-Pounds, Granules

BioAdvanced for southern lawns is another fertilizer designed to help your St. Augustinegrass survive the intense summers across the South. This fertilizer has the added bonus of pre-emergent herbicides and post-emergent herbicides to kill weeds already in your lawn and prevent more weeds from sprouting for six months after application. 

This fertilizer’s high-nitrogen content is perfect for keeping your grass thick and bright green during late spring and summer. Just be careful not to over-fertilize, as too much nitrogen will kill your grass. 

Specifications:

  • Type: Granular fertilizer 
  • NPK ratio: 35-0-3
  • Time release: Slow-release
  • Effective period: 8 weeks 
  • Package size: 12.5 lbs
  • Coverage area: 5,000 square feet 
ProsCons
Controls common lawn weeds such as dandelions, clover, dollarweed, and crabgrass

Perfect for warm-season grass types like St. Augustine

Phosphorus-free
Expensive 

Not for sale in all states

May not benefit your lawn if your soil needs supplemental phosphorus  

Where to buy:

Buyers Guide to Fertilizers for St. Augustine Lawns

We know not everyone is a lawn care aficionado who knows all the vocabulary words and what to look for in a lawn fertilizer. If some of our reviews left you confused, this guide will help you understand how to choose the best fertilizer for your St. Augustinegrass. 

Pro Tip: Don’t have St. Augustinegrass? Find information about choosing a fertilizer for your lawn in our reviews of the Best Fertilizers for Grass (all grass types) and the Best Fertilizers for Bermudagrass

St. Augustinegrass Fertilizer Needs

Each lawn’s nutrient needs vary based on the state of the soil underneath. But in general, St. Augustine lawns should get 1 to 1½ pounds of nitrogen per 1,000 square feet every 8 to 10 weeks during the growing season of spring and summer. 

In fall, when growth is much slower and the grass is preparing to enter winter dormancy, St. Augustine should get no more than ½ pound of nitrogen per 1,000 square feet in one feeding. In total, your lawn should never get more than 5 pounds of nitrogen per 1,000 square feet per year. 

How can you tell how many pounds of nitrogen your fertilizer contains? Look at the first number in the NPK ratio (the N), which tells you what percentage of the fertilizer is made up of nitrogen. Multiply that percentage by the size of the package to figure out the amount of nitrogen you’re applying to your lawn. 

  • Example: Pennington UltraGreen Lawn Fertilizer has an NPK ratio of 30-0-4, and the package contains 14 pounds of fertilizer. 
  • Calculation: 30% nitrogen (0.3) x 14 pounds of fertilizer = 4.2 pounds of nitrogen in one bag 

Use this calculation to figure out the amount of fertilizer you should apply to your lawn. Remember that the recommendations listed here are per 1,000 square feet, so you’ll need to adjust for the size of your yard. 

Different types of fertilizer are suited for application during different times of the year. Check the chart below to find out the best fertilization schedule for your St. Augustinegrass, along with which fertilizers would be best for each feeding. 

When to fertilize
St. Augustinegrass
Nutrient needs
at this time of year
Best fertilizer
at this time of year
Spring: 3 weeks
after the grass
greens up
and after the last
expected frost
(usually April)
Complete
fertilizer
with NPK ratio
of around 3-1-2
The Andersons PGF Complete Fertilizer with Humic DG
Summer:
8 to 10 weeks
after the first
feeding
(usually June)
High nitrogen,
little or no
phosphorus 
Pennington UltraGreen Lawn Fertilizer 
Early fall:
4 to 6 weeks
before temperatures
are expected
to drop below
55 degrees
(usually
September)
Lower nitrogen,
at least some
potassium 
The Andersons PGF Complete Fertilizer with Humic DG

What Does NPK Mean?

The NPK ratio is probably the most important thing to look at when choosing a fertilizer. NPK shows you what percentage of the three most important plant nutrients, also known as macronutrients, your fertilizer contains. 

The three macronutrients represented by the NPK ratio are:

  • Nitrogen (N) encourages your grass to grow faster and greener. Grass needs a lot of nitrogen, so this is almost always the highest number in the ratio. 
  • Phosphorus (P) helps your grass develop strong roots. New lawns need plenty of phosphorus to establish roots, but already established lawns don’t need it as much. Plus, stormwater runoff carries the phosphorus into natural bodies of water, where it causes algal blooms. Several states have banned phosphorus fertilizer because of this pollution. For these reasons, many fertilizers don’t include phosphorus. 
  • Potassium (K) makes your grass more resistant to lawn diseases (such as leaf spot, powdery mildew, and brown patch) and supports the overall health of the grass. 

Example: A fertilizer with an NPK ratio of 16-4-8 contains 16% nitrogen, 4% phosphorus, and 8% potassium.

Before you can choose the best NPK for your lawn, you’ll need to test your soil. A soil test will show which nutrients your lawn lacks or which ones it has too much of. And not just the NPK nutrients — a soil test is an in-depth analysis that will also show if your lawn needs a boost of lesser plant nutrients (called secondary nutrients and micronutrients). 

You can get a soil test from your local university extension by taking a soil sample and sending it by mail to their laboratory. Find your university extension through the National Institute of Food and Agriculture’s online directory

Different Types of Fertilizers

Besides various nutrient blends, there are many other differences between fertilizers. Which type of fertilizer you want to use for your St. Augustinegrass is up to your personal preferences. 

Here’s the basic rundown of some of the different types of fertilizers: 

  • Liquid vs. granular: Liquid fertilizers, which you apply with a sprayer, typically act faster with results you can see sooner, but they don’t last as long as granular fertilizers and need more frequent applications. Granular fertilizers, which you apply using a fertilizer spreader, might make you wait for your lawn’s green-up, but the results will last longer.
  • Slow-release vs. immediate-release: Slow-release fertilizers (aka controlled-release fertilizers) release nutrients into the soil slowly to feed your lawn continuously over the course of several weeks. Immediate-release fertilizers (aka fast-acting or fast-release fertilizers) release all their nutrients as soon as you apply them for quick results. You’ll need to apply immediate-release fertilizers more often, and there’s a higher chance that they’ll burn your lawn.
  • Organic fertilizers: Fertilizers made of organic matter typically cost more than synthetic fertilizers, but they have many benefits. Organic fertilizers improve your soil’s structure, increase the number of beneficial microorganisms in your soil, and don’t pollute the environment. Plus, they’re safe around pets and small children.
  • Lawn starters: “Lawn starter” fertilizers are designed specifically for newly seeded or sodded lawns. They contain a nutrient blend that’s gentle on the new grass and helps it get established quickly.
  • Add-ons: You’ll notice many fertilizers contain more than just fertilizer. Some have herbicides for weed control, pesticides for lawn pest control, or fungicides for disease prevention. These “add-ons” let you fertilize your lawn and prevent common problems at once without having to apply a second product. Fertilizers with add-ons invariably cost more than those without. 

Once you’ve chosen the best fertilizer for your St. Augustinegrass, see this video from Silver Cymbal for professional tips on how to fertilize with a spreader without causing stripes in your lawn, missing spots, or over-fertilizing and burning the grass: 

FAQ About Fertilizing St. Augustinegrass 

1. How do I make my St. Augustinegrass thicker?

St. Augustinegrass spreads on its own using aboveground stems called stolons. If you want your grass to grow thicker, encourage it to spread so that it fills in thin and patchy areas. 

Here are some tips to get your St. Augustinegrass to spread faster:

Apply nitrogen-rich fertilizer with phosphorus for root growthduring the growing season (late spring and summer).
Water your lawn more often than usual in summer. 
Mow your lawn less frequently than the usual once per week in summer. 

2. What is the best fertilizer for Palmetto grass?

“Palmetto” is one of the most popular cultivars of St. Augustinegrass. It’s naturally a more vibrant green than other varieties. Even though Palmetto grass looks a little different, its fertilization needs are the same as any other type of St. Augustinegrass, so any of the fertilizers in our top picks will work great. 

3. What happens if you over-fertilize St. Augustinegrass?

Over-fertilizing St. Augustinegrass will lead to nitrogen burning. Some symptoms of nitrogen burns include yellowing or browning grass and root damage. The over-fertilized sections of grass could die as a result. 

You’re especially at risk of burning your grass when using a nitrogen-rich, liquid, or fast-acting fertilizer. Use extra caution when applying these types of fertilizers. 

Basic St. Augustinegrass Maintenance 

Fertilizing your lawn with one of the best fertilizers for St. Augustinegrass will give your grass a huge boost while it’s actively growing in spring and summer. But proper fertilization is only one piece of the puzzle when it comes to keeping your lawn thick and healthy.

If you want a lush lawn year after year, follow these other St. Augustinegrass maintenance tips from Texas A&M University:

  • Keep your grass tall by setting your mower at 2½ to 3 inches in the sun or 3 to 3½ inches in the shade.
  • Wait to water the lawn until your grass shows signs of drought stress, including fading color or folded leaves (usually once every 5 to 10 days depending on the weather).
  • Select weed control products carefully because St. Augustinegrass is sensitive to some herbicides, including 2,4-D, MCPP, MSMA, and dicamba.
  • Watch for signs of common St. Augustine pests, such as chinch bugs and white grubs.
  • Improve water and nutrient flow by dethatching the lawn in April or May if the thatch layer has become thicker than ¾ inch.
  • Prevent compacted soil by aerating the lawn during St. Augustine’s growing season of late spring and summer. 

When to Call a Lawn Care Pro

NPK, liquid vs. granular, organic vs. synthetic, and fertilizer spreaders – like you have room for another tool in your garage? Proper lawn care might as well be a 1,000-piece puzzle. One of LawnStarter’s local lawn care pros can pick up some of those pieces to make your life that much easier and keep your St. Augustine lawn green and healthy. 

Main Photo Credit: Shutterstock

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Jordan Ardoin

Jordan Ardoin

Jordan Ardoin is a writer and indoor plant enthusiast hailing from Florida. In her spare time, she enjoys chasing her two cats around the house and trying to keep her houseplants alive.