5 Best Fertilizer for St. Augustine Grass [Experts Guide]

St. Augustine grass is a drought-tolerant, warm-season turfgrass that grows well in the southern United States. It can grow up to two inches per day during peak summer months and requires at least four hours of direct sunlight per day for optimal growth. St. Augustine grass does best with applications of fertilizer every three weeks from April through September to keep it looking green, healthy, and lush.

This blog post will discuss what is the best fertilizer for St. Augustine grass and provide detailed instructions on how to apply each type correctly so you can achieve your desired results.

Here are the top 5 best St. Augustine grass fertilizers. We made this list based on customer feedback, brand reputation, price, market analysis, personal opinion, and more.

5 Best Fertilizer for St. Augustine Grass Options For Your Lawn

Southern Ag Atrazine St. Augustine Grass Weed Killer
  • Controls emerged weeds and weeds from seed
  • Kills tougher weeds that are deep rooted
  • Fertilize the lawn
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Ortho Weed B Gon Weed Killer for Lawns Concentrate2
  • kills more than 250 types of weeds
  • Won’t harm the lawn when use as directed
  • Results in hours
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  • 6 months protection from weeds
  • Won’t harm your lawn when use directed
  • Feed and strengthen your lawn
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Scotts Turf Builder Southern Triple Action
  • Fertilize to build thick green lawns
  • increase heat and drought resistant
  • Kills weeds down to the roots
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Roundup for Lawns 6 Ready-To-Spray
  • Kill more than 90 types of weeds
  • Starts working immediately
  • Easy to use
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Southern Ag Atrazine for St. Augustine Grass

Best Overall
9.8/10 Our Score


  • CONTROLS Many common grassy and broadleaf weeds
  • Thickens the lawn to crowd out weeds
  • Provides suppression of crabgrass


  • Kill many broadleaf weeds
  • Does not kill grass
  • Destroy the crabgrass
  • Used on centipede and st. augustine grass


  • Cause illness if ingested
  • Cannot be used with hose end sprayer

Southern Ag Atrazine St. Augustine Grass Weed Killer is great for use on St. Augustine and centipede lawns. These grass have a sensitivity to other types and herbicides out there. It’s really good as a pre-emergent. But can be applied during growing and dormant periods.

This formula controls emerged weeds and weeds from seeds. When it comes to hard kill weeds in your St. Augustine grass, Atrazine is the best product of choice.

For best results, apply Atrazine to St. Augustine grass in early spring or during dormant periods when the weeds are young. Never spray Atrazine on windy days because it will drift onto other plants.

To apply, you want to mix this at four-point, three ounces per gallon of water and that will cover five hundred square feet. So, depending on the lawn. You’ll have to do the math to figure out your mix in your tank. When you mix this, you want to apply it from a spray tank. This product does need to be watered approximately seven to ten days after application. Not recommended for use with a hose-end sprayer.

Wear gloves, protective clothing, and eye protection during application. Wash up well afterward. Always read the instruction before use.

Ortho Weed B Gon Lawns

Best Concentrate
9.8/10 Our Score


  • Kills dandelions, clover and other broadleaf weeds
  • Quick action formula
  • Grow more green and thick lawn
  • Easy to apply


  • Kills the weeds, not the lawn
  • Rainproof in 1 hour
  • For northern and southern lawn


  • Not recommended for Floratam grass

Ortho Weed B Gon Weed Killer is the perfect solution for most of the northern and southern grass types to kill dandelions, clover, dollarweed, and other broadleaf weeds all the way to the root. While it does not harm your lawn when used as directed. You’ll see tough results on weeds after only a day.

One of the most significant advantages of Ortho Weed B Gon Lawns is its ability to target weeds while leaving the grass unharmed. This makes it a safe and effective option for homeowners who want to maintain a healthy lawn without damaging their turf. The product’s fast-acting formula means that visible results can be seen within hours of application, providing a quick solution for homeowners who want to rid their lawns of weeds.

The ready-to-use one-touch comfort wand is great for quickly spot-treating small or large areas. But when you need to kill an army of weeds. Apply this product when weeds are actively growing.

This product is recommended for Bermudagrass, St. Augustine (excluding Floratam), Centipede, Buffalograss, Bluegrass, Bahiagrass, Ryegrass, and Zoysia.

Just connect the hose directly to the tank sprayer or the dial-in spray.

Best Weed and Feed for St. Augustine Grass: 3-IN-1 WEED AND FEED

Best Weed & Feed
9.8/10 Our Score


  • prevents broadleaf, grassy weeds, and crabgrass
  • 50% Slow release formula
  • Guarantee results
  • N-P-K: 35-0-3


  • Kill weeds including dollarweed, clover, nutsedge
  • Feed, greens and strengthen your lawn
  • Won’t harm your lawn when use directed
  • Slow release formula


  • Do not rake after application

BioAdvanced 3-IN-1 Weed and Feed is specially formulated for southern lawns. It kills listed weeds including dollarweed, dandelion and clover, and crabgrass. Feed, green, and strength your lawn. Just one application delivers up to 6 months of protection.

3-IN-1 weed and feed work on all four major southern turf types including St. Augustine, Bermudagrass, centipedegrass, and zoysiagrass.

It’s like three products in one, save your time and money. Make one application instead of buying and applying weed and feed products around the season.

Apply to only actively growing turf. In spring, mow your lawns two times. This ensures your lawn emerges from dormancy. 3-IN-1 weed and feed is a granular product. You can apply with a drop-type spreader. Check the spreader setting for the application.

Treat the border of your lawn first, then fill the center by making parallel passes. Be sure to avoid overlapping.

Remember to sweep, brush or blow any access granules from the sidewalk, patios, and driveway, back onto the lawns. You get a thicker and greener lawn, longer roots, and rich soil.

Once the 3-IN-1 weed and feed is down, wait 24 hours and lightly water in. This will activate the crabgrass barrier and last up to 6 months.

You can make the second application in the fall. It will kill dollarweed and prevent poa annua. Check the label for timing and application. Once you applied, do not rake your lawn. Because heavy raking can break up the weed barrier.

Follow these tips and label instructions for the cast and time-saving benefits of the product.

Scotts Turf Builder Southern Triple Action

Best Value
9.8/10 Our Score


  • Feed and strengthen your lawn
  • Prevents and kill fire ants
  • easy to use
  • N-P-K: 29-0-10


  • Kills the weeds
  • Feed the lawn
  • Prevents the weeds to grow
  • Strengthen heat and drought resistant


Scotts turf builder southern triple-action kills the toughest weeds including dandelion chickweed, oxalis, plantain, and clover from the lawn. This application also kills fire ants, fleas, mole crickets, and chinch bugs. And fertilize your lawn for building thick, green, and healthy lawns.

Scott’s turf builder works on all major southern turf types including St. Augustine, Bermudagrass, centipedegrass, and zoysiagrass.

Scott’s turf builder can be applied when weeds are actively growing. Apply this product directly to the lawn area. And do not water to the point of runoff. Do not apply more than twice per year.

This product is easy to use. Just collect the size of the area. Put into the spreader and adjust the setting of the spreader according to the label and apply. This product strengthens your lawn against heat and drought resistance.

Apply this product once in the spring and once in the fall. Use this product to a dry lawn with the spreader. The product must be water in after application immediately.

Roundup for Lawns Fertilizer for St. Augustine Grass

Editor Choice
9.8/10 Our Score


  • Specifically formulated for Southern grass types
  • Kill the toughest weeds down to the roots
  • Kill more than 90 types of weeds
  • Easy to use


  • Kill weeds, not the lawn
  • Covers up to 6000 square feet
  • Starts working immediately


  • Not recommended for dichondra, carpetegrass, and desirable clover
  • Avoid applying in fall or winter

Roundup Ready-To-Spray kills the toughest weeds including dollarweed, clover, dandelion, yellow nutsedge, and 90 other listed weeds down to the roots.  The formula is specifically designed to kill the weeds, not the lawn.

It’s the best weed and feed spray for southern grasses, such as St. Augustine (including Floratam), Centipedegrass, Bermudagrass, and Zoysia. Remember, do not use this product on bentgrass, carpetgrass, dichondra, and the desirable clover.

This formula works best when weeds are actively growing. It stops the growth of the weed and kills the weeds down to the roots, so weeds won’t come back.

Simply connect it with the garden hose spray, turn on the water and start spraying. Shake well before using. People and pets may enter the treated area after the spray has dried.

Best Fertilizer for St. Augustine Grass Buyer’s Guide

Things Our Experts Considered When Selecting the Best Fertilizer for St. Augustine Grass

A good fertilizer is essential for thriving plants. The first step in choosing a fertilizer for St. Augustine grass is to have the soil tested and figure out if it lacks any nutrients because this will help you make sure that your chosen product isn’t harmful or too much of one specific element (like phosphorus).

Most communities offer county extension agencies where they’ll test these things so don’t worry!
A wide variety of lawns can be fertilized with the same general types – just keep an eye out on how often each application needs to be done with different soils since some may need more frequent doses than others depending upon their condition.

N-P-K Ratio

Lawn and turf fertilizers are labeled with the amounts, by weight, of three specific nutrients they contain: Nitrogen (N) brings out the color in your grass and speeds growth. Phosphorus encourages bud or seed formation while potassium helps you have healthy plant life. While all three nutrients help St Augustine grasps grow well, one that soil lacks most is nitrogen

Post or Pre-emergent

Two main types of herbicides are available pre-emergent and post-emergent. Pre-emergent herbicides work by preventing weeds from growing. Post-emergent, on the other hand, attacks actively growing weeds in your St. Augustine grass lawn.

For best controlling the weeds, apply the pre-emergent fertilizer during the daytime when no rain is expected within 24 hours for four consecutive days.

Fall applications help prevent winter annuals and other weeds from popping up; in fall, wait until nighttime lows remain between 55 and 60 degrees Fahrenheit for four consecutive days, typically in September.

After applying granular pre-emergent application over the lawn, make sure to apply one and half an inch of water immediately.

A common crabgrass preventive product containing benefin and trifluralin recommends applying at a rate of 2 ¼ to 3 ¼ pounds of granules per one thousand square feet of turf. Products vary inactive ingredients and application rates; read the instructions carefully before applying.

Pre-emergence herbicides are the best weapon against crabgrass. If you can apply it in time, the pre-emergent herbicide is the best to use for St. Augustine and other grasses because it prevents the germination of weeds.

How to Plant and Grow St. Augustine Grass

Liquid vs. Granular vs. Water-Soluble

Lawn fertilizers can be categorized as either liquid, granular, or water-soluble. The form of fertilizer that works best for your lawn is largely dependent on personal preference and needs.

  • Liquid Fertilizers

Liquid fertilizers are a quick and easy way to boost your lawn’s growth. With liquid fertilizer applied, new shoots of grass can be seen within 3 or 4 days after application on St. Augustine turf – making them an excellent choice for those who do not have time during their workday schedule.

This type of product also has another advantage: since it is quickly absorbed into the ground without fully dissolving in soil moisture content which leads us back towards applying more often than granular fertilizers would require (due only partially being adsorbed onto roots).

  • Granular Fertilizers

A granular fertilizer has many of the same nutrients as liquid fertilizers. They differ slightly in that these slow-release, highly concentrated blocks can be released over time for easier access by roots and will give you less rapid greening up but typically require much smaller applications than with a liquid product. It’s applied using a fertilizer spreader.

  • Water-Soluble Fertilizers

Though this fertilizer comes in a granular form, it’s not meant to be applied with the spreader. Instead, water-soluble fertilizers are made for applying by connecting to your garden hose and dissolving into a solution that can green up the lawn fairly quickly when used properly.

Also Consider

  • Fertilizing your lawn is just as important as proper care of the grass. After turning green, St. Augustine should be fertilized with an all-purpose fertilizer that contains high levels of nitrogen for 6 – 8 weeks before being started again in spring only after their first application when they are still young and trying out life on Earth.
  • Make sure you don’t end up damaging this precious grass by applying too much or at the wrong times during growth stages.
  • A high-nitrogen fertilizer can be applied a month later, followed by periodic applications during the growing season. Stop fertilizing in fall approximately 1/2 way through your application schedule when outdoor temperatures have cooled to around 55 degrees Fahrenheit or less for St. Augustine grass – this will allow it time to go dormant so that you do not need any nutrients until springtime.

Reading the label

Before applying any herbicide, it’s important to know what to look for on the label. Herbicide products often target only a certain selection of weeds. First find out, what weeds you have growing on your lawn.

To know whether or not the product you choose is safe for St. Augustine grass read the product label to see if it is listed for use on St. Augustine grass.


How to Care For St. Augustine Grass?

St. Augustine grass is a popular choice for lawns in warmer regions due to its high tolerance for heat and humidity. Proper care is essential to keep it healthy and looking its best. Here are some tips for caring for St. Augustine grass:

  1. Watering: St. Augustine grass needs consistent moisture to thrive, but overwatering can cause problems. Water deeply and infrequently, providing 1 inch of water per week during the growing season. Avoid watering in the evening, which can lead to fungal diseases.
  2. Fertilizing: St. Augustine grass requires regular fertilization to maintain healthy growth. Apply a slow-release fertilizer in the spring and summer, following the manufacturer’s instructions.
  3. Mowing: St. Augustine grass should be mowed regularly to a height of 2-4 inches. Avoid mowing when the grass is wet, as this can damage the blades.
  4. Weed Control: Keeping weeds under control is important for maintaining a healthy St. Augustine lawn. Apply a pre-emergent herbicide in the spring and fall to prevent weeds from germinating. Hand-pull any weeds that do appear.
  5. Pest Control: St. Augustine grass is vulnerable to pests such as chinch bugs and sod webworms. Keep an eye out for signs of infestation, such as yellowing or thinning patches of grass. Treat with an appropriate insecticide if necessary.
  6. Aeration: St. Augustine grass can benefit from periodic aeration to relieve soil compaction and improve water and nutrient absorption. Aerate in the spring or fall, when the grass is actively growing.

When to Apply Fertilizer to St. Augustine Grass?

A spring feeding should happen about a week or two after the grass has greened up. After that, apply fertilizer according to what kind and how strong it is. So, follow package directions carefully. Generally speaking, every 4-6 weeks will be enough for your lawn’s needs though – don’t use more than this as overdoing things might do harm instead of good in some cases (especially if you live far from water).

How to Apply Fertilizer for St. Augustine Grass?

Fertilizers can be applied efficiently through various means such as garden sprayers or spreader disks depending on their consistency requirements. If water-soluble products must also have incorporated into the soil then attach them with hoses and end dispensers.

Should St.Augustine Grass be Watered After Fertilizing?

Do not Apply water when fertilizing liquid fertilizer. But you can apply water for 2 to 3 days before when applying granular products.

Quick Recommendations

When it comes to selecting the best fertilizer for St. Augustine Grass, there are many variables that must be considered including soil type, plant health, and frequency of application. Soil should be tested before applying any fertilizer to ensure you know your specific needs.

BioAdvance 3 in 1 weed and feed is the best product for St. Augustine Grass. It feeds the grass and prevents the weeds.





Jon Dunn
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Jon Dunn has 12 years of experience as a seed and fertilizer specialist at the North Carolina Department have been immensely rewarding, and he looks forward to continuing to contribute to Lawnscanner. Read more