9 Best Fertilizers for St. Augustine Grass in 2023

Choose the right fertilizer to grow a lush and healthy St. Augustine grass lawn from our list of nine highly recommended grass fertilizers. We’ll also explain the proper way to apply these St. Augustine fertilizers.

Sean Stratton | Updated April 23, 2023

St. Augustine grass is one of the most popular grass types due to its deep blue-green color and tolerance for heat and humidity. With proper soil maintenance, it makes your lawn the envy of the neighborhood.

Having tested 9 of the best-selling options on the market, I’ve compiled a list of the 9 best St. Augustine grass fertilizers to keep your St. Augustine grass lush and healthy.

9 Best Fertilizers for St. Augustine Grass

saint augstine grass

1. Pennington UltraGreen Starter Fertilizer

The best overall fertilizer for St Augustine grass is the Pennington UltraGreen Starter Fertilizer. It has an NPK ratio of 22-23-4 and 5% iron which helps lawns achieve a deep, dark green color.

This balanced ratio of nutrients helps the development of strong roots and lush grass blades. Its slow-release formula also means that your lawn will be continuously fed for up to 3 months with just one treatment.


  • Comes in resealable packaging.
  • Easy to use and spread the fertilizer.
  • Comes with 5% iron for a lush green St Augustine lawn.
  • 5000 sq. ft. coverage area


  • Over-fertilizing can damage the lawn

2. Super Juice All-in-One Soluble Supplement Lawn Fertilizer

If you are looking for a balanced fertilizer for your lawn, you should look at this Doc’s Super Juice fertilizer. It has a 14-2-4 N-P-K ratio which ensures a good combination of Nitrogen, Phosphorus, and Potassium for your St Augustine lawn. If you want to use it at full strength, the ratio will be 14-2-4. You can also use it at half-strength, and the ratio will be 7-1-2.

This fertilizer comes in a dry mix for easy application. Just mix it with water and spray it on the lawn directly. This allows you to apply it evenly.

It’s filled with the goodness of micronutrients like copper, magnesium, manganese, sulfur, zinc, and 4% iron to improve the health of your lawn.


  • The fertilizer is easy to mix and spread evenly.
  • Contains micronutrients like magnesium, iron, and zinc.
  • Can be used with full or half-strength according to your need.


  • More expensive

3. Milorganite 0636 Organic Nitrogen Fertilizer

If you prefer a slow-release fertilizer for your St Augustine lawn, you should check out this Milorganite 0636 Organic Nitrogen Fertilizer with an NPK ratio of 6-4-0. It slowly releases vital nutrients while improving soil quality. While synthetic fertilizers target the roots of the grass, this fertilizer targets the soil to create longer-lasting results.

Plus, this slow-release fertilizer formula means that you only need to apply it every 10 weeks, and it will also reduce lawn mowing frequency as the grass grows slower.

Milorganite says: this eco-friendly Nitrogen fertilizer is derived from recycled nutrients produced by the water reclamation process. So, you don’t need to worry about your safety, your kids, and your pets.


  • Covers a wide area; suitable for golf courses.
  • It’s eco-friendly, so it’s safe for kids and pets.
  • Being slow-release reduces the hassle of applying quite often.
  • Affordable


  • It’s not a highly-recommended choice for Bermuda grass.
  • Doesn’t contain potassium

4. Simple Lawn Solutions Extreme Grass Growth Lawn Booster

If your primary concern is developing a solid root system, then Simple Lawn Solutions Extreme Grass Growth Lawn Booster is the solution. It has an NPK ratio of 6-18-0. The higher phosphorous levels ensure better root development. This is ideal for new lawns, whether you’re starting from seed or sod.

The liquid formula and spray nozzle make it super easy to apply. Just hook up to your hose and spray over your lawn.


  • Easy to spray and use
  • The coverage area of 3,200 square feet
  • Enhances seed germination
  • Humic acid boosts optimal nutrition intake


  • No potassium
  • There are better options if you have an established lawn

Next Read: Top Potato Fertilizers

5. Southern Ag Chelated Liquid Iron, 128oz -1 Gallon

If your primary objective is to make your lawn greener or to correct yellowing spots, then this liquid iron is for you.

If you notice yellow patches in your lawn, then your grass is probably lacking a vital nutrient, iron. This fertilizer treats any iron deficiency that your lawn may have. It contains 5% soluble iron and 3.5% chelated iron combined with sulfur. Apply this to your lawn to revive the lush green St. Augustine turf you always wanted.


  • Makes your grass green
  • Treats iron deficiency
  • Can also be used on flowers, trees, and shrubs


  • Expensive
  • Only contains iron

6. Scotts 21814 Turf Builder Starter Food for New Grass

If you are starting your St. Augustine lawn from seedlings, then Scotts Turf Builder is your ideal turf builder. This fertilizer is specially formulated for new lawns and advertises 70% thicker grass with 35% quicker growth than unfed grass.

It has an NPK ratio of 24-25-4. These high levels of nitrogen and phosphorus ensure fast root and blade growth for your St. Augustine lawn.


  • Thicker grass
  • Faster growth
  • Gives coverage for up to 14,000 square feet of lawn.
  • Yields a strong upshot for seedlings.


  • A specific type of spreader is needed, which may add to your hassle.

7. Scotts EZ Patch Lawn Repair For St. Augustine Lawns

If you’re having problems with specific patches on your St. Augustine lawn, try Scotts EZ Patch Lawn Repair!

It is an easy-to-use mulch and fertilizer in one solution. Add it to any problem lawn patch, and you’ll see an improvement within 15 days.


  • Repairs grass 60% faster
  • Creates a moist and protective shield
  • 6x more water-absorbent
  • Treat an area up to 85 square feet
  • No extra mixing needed


  • Error in the steps of using may lead to weed bait.

8. Leso SeedRanch St. Augustine Lawn 24-2-11 Fertilizer

SeedRanch St. Augustine Lawn Fertilizer is a professional-grade fertilizer that contains 6% iron and an NPK ratio of 24-2-11. This combination ensures fast-growing green grass for your lawn. It also has a large coverage area of 12,000 sq. ft.


  • Grants extra greening to grasses.
  • Coverage of 12,000 square feet.
  • Easy to dissolve in water.


  • Overfertilizing can burn the grass

9. Extreme Grass Growth Lawn Booster

If you are looking for an excellent liquid fertilizer for your St. Augustine turf, go for Extreme Grass Growth Lawn Booster!

It is a balanced fertilizer (16-4-8 NPK) with a blend of all the essential nutrients warm-season grass needs. It also treats common fungi and weeds.

You won’t need to find any extra tools to use it. Just fit the hose right over the bottle mouth and spray to spread all over your turf. That’s all!


  • A balanced fluid lawn food.
  • NPK 16-4-8.
  • Ensures root vigor.
  • Treats up to 3,200 square feet of yard.


  • Not fit to use in winter.

Nutrition to Look for in St Augustine Grass Fertilizers 

When researching fertilizers for your lawn, the information you come across can be overwhelming. Let us break down some of the most common terms you’ll encounter during your search.

What is NPK?

  • Nitrogen (N) is a macronutrient that speeds up the growing process and makes grass greener.
  • Phosphorus (P) is a macronutrient that promotes root growth and adds vigor.
  • Potassium (K) is a macronutrient that strengthens the grass’ immunity and resistance to disease.

Also Read: Epsom Salt for Tomato Plants

What to Consider when Buying Fertilizer for St Augustine Grass?

Applying a good quality fertilizer will improve your St Augustine grass. But it’s quite a difficult thing to find a fertilizer that will benefit your St Augustine lawn with minimal effort. That’s why to get the best results from a fertilizer, here are some things you need to consider.

1. Organic or Synthetic Fertilizer

No matter which fertilizer you choose, your first concern should be ‘safety’ for you and the environment. When talking about safety, what can be a better option than organic fertilizers? Yes, we do agree that organic fertilizers are a safer option. However, safety is not the only thing we should be concerned about, we need to think about efficiency as well.

Synthetic fertilizers are more likely to show faster results compared to organic fertilizers, but they may also damage the natural balance of pH in the soil. Oh, one more thing, don’t forget the smell! Organic fertilizers have a more pungent smell than synthetic.

So, choose the one that you are comfortable with. And if you choose synthetic fertilizer, ensure you don’t use too much of it.

2. Quick-release or Slow-release

A quick-release fertilizer will give you results rapidly. If you want to see your lawn thrive quickly, this is what you need. However, you will remain busy throughout the grass growing season because you must apply the fertilizer multiple times.

A slow-release fertilizer will work slowly and keep providing nutrients to your grass for a long time. You may not notice changes quickly, but the results will last longer.

3. Types of Fertilizers

Granular: Granular fertilizers are generally slow-releasing. Its benefit is that it will provide nutrients for a comparatively longer time. Another great thing about this fertilizer is that you won’t need to fertilize frequently.

Liquid: If your goal is to achieve results quickly, you can opt for liquid fertilizers. The liquid usually gets absorbed quickly, so you can see results in as little as a week! But liquid fertilizers may require frequent application.

Water-soluble: Water-soluble fertilizers look like granular fertilizers, but they can dissolve in water and are fast-acting.

4. N-P-K Ratio

The term N-P-K ratio means the ratio of Nitrogen, Phosphorus, and Potassium in a fertilizer. All of these nutrients are important for the healthy growth of St. Augustine grass.

Key-Takeaway: choose a fertilizer that not only ensures a balanced N-P-K ratio but also provides enough Nitrogen so that your St. Augustine grass gets better growth. You can also get a soil test to help you understand which nutrients your soil lacks.

Frequently Asked Questions

When it comes to maintaining the elegant St. Augustine grass with fertilizer and manure, the question “When to fertilize?” is quite crucial. Let’s look at the best times to fertilize.

April to May

Look for a complete fertilizer with an NPK ratio of 3-1-2.

June to August

It is the time of the sowing year when you can go for a fertilizer rich in nitrogen with low phosphorus.

September to October

Use a fertilizer with a lower ratio of nitrogen and potassium.

It’s important to grasp the dos and don’ts of applying fertilizer to your lawn because overfertilizing can damage your soil and grass.

Here are some things to keep in mind when fertilizing:

  • Test your soil to find a fertilizer with the proper NPK ratio for your lawn.
  • Water your lawn a few days before fertilizing.
  • If you use a spreader, adjust the settings according to the instructions on the fertilizer bag.
  • Apply the fertilizer according to the specific instructions on its packaging.
  • Water your lawn approximately 1 to 1.5 inches per week, depending on rainfall.
  • Fertilize every ten weeks when your grass is in its growth stage.
  • When the weather gets cooler, apply potash to your lawn. Potash is a lawn booster made up of salt that contains potassium in a water-soluble form. It is ideal for fertilizing st. Augustine grass in the winter because it helps your grass resist cold, drought, and disease. When looking for a fertilizer rich in potassium, look for a higher K value in the NPK ratio.

Applying the right amount of fertilizer is extremely important because if you apply the fertilizer in a small amount, your lawn will remain hungry, and you will not get to see that beautiful lush green lawn you were looking for. And if you apply too much fertilizer, you will burn your turfgrass.

So, you can follow this simple rule of applying fertilizer where you must maintain 1 pound of nitrogen for a 1,000 sq. ft. lawn. For more extensive areas, the rate will increase while maintaining the ratio. However, this may not be accomplished like a piece of cake because the N-P-K level of fertilizers may vary from brand to brand.

That’s why you need to divide the number of Nitrogen (N) from the N-P-K ratio of the fertilizer by 100. You will find the N-P-K ratio on the label of the fertilizer. Next, we need to multiply the resultant number by 1000. After that, divide 1000 by the product of that multiplication. The resultant number will be the amount of fertilizer (in pounds) you need for a 1,000 sq. ft. lawn.

Here are the 6 steps to making your St. Augustine grass thicker.

Prepare the Soil: Acidic soil with proper drainage is an ideal duo for St. Augustine grass. So, if you want a thriving lawn, ensure proper draining and a pH level in the 5.0-8.5 range.

Plant Early: Plant the seed plugs or sods in early summer. The moist and warm summer soil will help your grass achieve healthy growth to tolerate the higher temperature when summer is at its hottest.

Properly Fertilize: Choose a fertilizer with the appropriate nitrogen, phosphorous, and potassium ratio for your lawn. Test your soil sample to find the proper ratio for your specific needs.

Watering and Drainage: When it comes to lawns, overwatering can be just as harmful as underwatering. You must maintain a proper watering schedule and ensure proper drainage. St. Augustine grass needs about 1 inch of water per week. Early morning is also the most optimal time to water your lawn.

Controlling Weeds: Hand pluck the weeds or use a particular type of mild herbicide to control weeds. Choose the herbicide carefully and test it on a small patch of grass first to ensure it doesn’t do more harm than good.

Proper Mowing: Mowing at the right time will keep your grass healthy and give your lawn a fantastic look.

After fertilizing, it’s vital to ensure your St. Augustine grass gets proper watering. This will help break down the fertilizer and kickstart providing nutrients to your plants. However, don’t rush to water your lawn just after fertilizing. To get better results from the fertilizer, wait at least 24 hours before you shower your lawn.

Written by Sean Stratton

Sean Stratton

Hi, I'm Sean, the senior editor here at Fertilizer Pick. I grew up on a farm in North Carolina and have grown fruits, vegetables, and trees since childhood. While I no longer live on a farm today, I still enjoy spending time on my garden and sharing my knowledge with friends and fellow garden enthusiasts.