When To Fertilize St. Augustine Grass?

As a longtime gardener and turfgrass enthusiast, I’m regularly asked for tips on properly fertilizing St. Augustine grass. This iconic southern lawn grass is prized for its lush, emerald hue and carpet-like density. However, without proper nutrition, St. Augustine will quickly lose its vigor and attractiveness.

The key is understanding when and how to fertilize St. Augustine for optimal health and beauty throughout the growing season. In this article, I’ll share insights from years of hands-on experience feeding this grass in my own yard and clients’ landscapes.

We’ll explore why fertilizer is so important for St. Augustine, look at ideal timing during spring, summer, and fall, and review suitable fertilizer types and application rates. I’ll also provide tips for fertilizing dormant St. Augustine to prep it for winter. Proper fertilization ensures your St. Augustine thrives from the first green shoots of spring through the killing frosts of winter.

Whether you’re dealing with nutrient deficiencies or simply want to maximize the performance of your St. Augustine, you’ll find the tips you need here. Let’s get growing and create the lush, dense, emerald turf that St. Augustine is known for when properly fed!

Why Fertilize St. Augustine Grass?

As a longtime gardener, I’m regularly asked why fertilizer is so crucial for St. Augustine lawns. This vigorous, spreading grass forms a lovely emerald carpet when properly fed and cared for. But skimp on nutrients, and you’ll quickly notice thinning and yellowing.

St. Augustine is a hungry grass with high nutritional demands. This species evolved in tropical environments where soils tend to be naturally fertile and rainfall plentiful. St. Augustine expects a rich nutritional environment.

My personal experience caring for St. Augustine has proven that fertilization is essential to bring out its best traits. Here’s why this grass needs regular feeding:

Fuels Growth and Spreading

St. Augustine flourishes when supplied with steady nutrition. Fertilizer provides essential macronutrients like nitrogen, phosphorus and potassium that facilitate rapid growth and lateral spread.

Abundant nitrogen in particular powers the production of new leaf tissue and above ground stolons. Phosphorus supports root and rhizome growth. Potassium enhances overall plant health.

By feeding it regularly, you’ll notice your St. Augustine filling in bare spots and expanding vigorously during the warm season. Proper fertilization delivers the raw ingredients for growth.

Maintains Rich Color

That trademark deep emerald hue of healthy St. Augustine depends on adequate nutrition. Nitrogen in particular is crucial for rich green coloration.

As a St. Augustine lawn becomes nitrogen deficient, the grass blades progressively yellow and lose their lush appeal. Adequate iron and micronutrients are also required to maintain ideal color.

Routine fertilization replenishes the nutrients that St. Augustine needs to sustain deep green leaves. Proper feeding keeps your lawn colorful all season long.

Supports Thick Turf

St. Augustine forms a lush, dense mat when supplied with balanced nutrition including nitrogen, phosphorus and potassium. Fertilizer powers the production of new shoots and stolons.

As fertilizer is withheld, St. Augustine grows more slowly and thinly. Bare patches begin to appear as growth and vigour decline.

By feeding routinely, you promote the thick, resilient turf that feels so lush and cushiony under foot. Fertilizer inspires St. Augustine to grow aggressively and knit together.

Prevents Nutrient Deficiencies

St. Augustine needs significant amounts of macro and micronutrients to perform at its best. These nutrients are depleted over time as grass grows and clippings are removed.

Fertilization replenishes nutrients like nitrogen, iron, manganese and zinc that St. Augustine depends on. It prevents depleted soils from limiting growth.

In summary, fertilizing supplies complete, balanced nutrition to fuel rapid growth, deep color and lush density that makes St. Augustine the iconic southern lawn grass. Don’t let your St. Augustine starve – feed it properly!

Fertilizing St. Augustine Grass

When To Fertilize St. Augustine In Spring?

As a St. Augustine caretaker for many years, I’m often asked when to begin fertilizing in spring. This vigorous grass breaks dormancy earlier than other warm season grasses, so timing is important. Start too early, and growth surges can occur when St. Augustine is still vulnerable to frost. But begin too late, and you miss key early season nutrient uptake.

Through trial and error on my own lawn, I’ve dialed in on ideal spring fertilization timing for St. Augustine. Here are the key factors I consider each spring to schedule applications just right:

Wait Until Soil Temps Exceed 55°F

Soil temperature should be the ultimate determinant of when to begin spring feeding. Consistent overnight lows at or above 55°F indicate dormancy has broken.

Feeding too early while ground is still cold won’t harm St. Augustine but will waste product. The grass can’t effectively absorb and utilize fertilizer nutrients below this soil temperature threshold.

I begin routinely checking soil temps using a probe in late winter. Once the thermometer shows 55°F or better several inches down, it’s time to fertilize.

Allow 2-4 Weeks After Greenup

Even if soil temps are warm enough, don’t rush to fertilize at the first signs of spring greenup. Give the St. Augustine 2-4 weeks to resume active growth before feeding.

Early greenup may just be chlorophyll production in crowns and stems. Wait until new leaf blade growth is visible to ensure nutrient uptake.

Let Frost Risk Pass

While St. Augustine will green up faster than other grasses, avoid very early fertilization. Late frosts can still damage freshly awakened St. Augustine. Wait until last expected frost passes.

I watch weather forecasts closely before beginning spring fertilizer programs. If long-range predictions suggest cold snaps, I delay feeding until safer conditions arrive.

Use a Low Dose First Application

For the earliest spring application, use a half rate or low nitrogen food. This provides a gentle wakeup call to dormant roots and microbes.

Save the high nitrogen foods for late spring when growth accelerates. The first application is simply to dust off the system and prepare for more aggressive feeding.

In summary, soil temperature, visible greenup, frost risk passing, and conservative initial rates all factor into optimal spring fertilizer timing. Be patient, then nourish your St. Augustine properly to kickstart an incredible growing season!

Best Fertilizers And Application Rates For St. Augustine

When it comes to feeding St. Augustine grass, product selection and application rate are just as important as timing. Through years of hands-on experience, I’ve dialed in the ideal fertilizers and feeding rates to maximize the health and beauty of St. Augustine lawns.

Use Balanced, Slow-Release Formulations

St. Augustine thrives on a steady diet of nitrogen. But too much soluble nitrogen applied at once causes surges of weak growth.

That’s why I recommend using balanced fertilizers with about 50% slow-release nitrogen for St. Augustine. Many coated urea products provide longevity. Sulfur coated urea is an excellent choice.

The phosphorus and potassium in balanced foods support rooting and overall plant health. Slow-release nitrogen prevents rapid growth flushes that require frequent mowing and increase disease risk.

Apply 1 Pound of Nitrogen Per 1,000 Square Feet

As a general rule of thumb, apply 1 lb. of nitrogen per 1,000 square feet of St. Augustine every 6-8 weeks during active growth. Limiting nitrogen keeps growth manageable.

For a fertilizer with 20% nitrogen content, this equals about 5 lbs. of product per 1,000 square feet per application. Read labels closely to determine amount needed to achieve 1 lb. nitrogen.

I tend to use slightly less nitrogen in early spring and again in fall. Excess nitrogen prolongs late season growth, reducing cold tolerance. But St. Augustine eagerly absorbs nitrogen through late summer.

Don’t Exceed 1 Pound of Nitrogen

Some mistakenly believe applying more fertilizer than recommended will make St. Augustine even greener and thicker. But too much nitrogen causes more problems than benefits.

Over-fertilization forces excessive top growth, increasing water needs. St. Augustine becomes soft and susceptible to disease pressure. Overfed grass also needs frequent mowing.

Stick within the recommended nitrogen rates to maintain healthy moderation in growth and appearance. More is not better when fertilizing St. Augustine grass.

In summary, a balanced, slow-release fertilizer applied at 1 lb. nitrogen per 1,000 square feet every 6 to 8 weeks gives St. Augustine the steady nutrition it thrives on without risk of overfeeding.

How To Fertilize Dormant St. Augustine Grass?

As St. Augustine grass goes dormant in fall and winter, many homeowners wonder if fertilization should continue. I’m often asked when to stop feeding and whether dormant St. Augustine needs any nutrients.

Through years of trial and error, I’ve learned dormant grass can still benefit from limited fertilizer applications. Here are my tips for proper winter feeding:

Continue Fertilizing Through Early Winter

In fall, reduce the frequency and nitrogen levels of your St. Augustine fertilizer program. But don’t cease feeding entirely once growth slows.

I advise applying one final fertilizer application in early winter, even after frost causes dieback. While St. Augustine won’t green up in response, the nutrients support root health during dormancy.

Use a Low Nitrogen Formula

Look for fertilizers in the range of 3-5% nitrogen for winter applications on dormant St. Augustine. Soluble nitrogen which triggers growth is not beneficial now.

Instead, lean on phosphorus, potassium, and micronutrients. These support internal root processes to protect the grass through cold weather dormancy when photosynthesis halts.

Apply Potassium for Cold Tolerance

Potassium is particularly valuable for winter applications. Potassium strengthens cell walls and improves the grass’s cold tolerance.

Buildup of sugars and starches also enhances freezing resistance. Potassium aids this process along with protecting cellular function when plants are untrivial.

Stop Fertilizing Once Dormant

Time your final dormant feeding just before expected frosts or freezes. Apply when daytime highs are still around 50°F for nutrient absorption.

Once St. Augustine is noticeably browned and clearly dormant, fertilizer applications are no longer beneficial. Avoid feeding on frozen ground, as nutrients won’t penetrate.

Resume in spring once soil temperatures reach 55°F for 2 consecutive weeks. This signals the grass is breaking dormancy and ready to utilize nutrients.

Proper winter fertilization prepares St. Augustine for dormancy while ensuring it awakens vigorously. Ample reserves aid spring greenup and transition back to active growing mode.


Should I fertilize St. Augustine before or after mowing?

As an experienced gardener, I’m often asked about fertilizer timing relative to mowing. Applying fertilizer too soon before or after cutting St. Augustine can damage the grass. Follow these tips:

  • Never fertilize immediately before mowing. Dry granular fertilizer will damage exposed leaf tips after cutting.
  • Avoid fertilizing immediately after mowing. Leaf tissue should be present to intercept nutrients. Mowing removes the blades that take in nutrients.
  • Ideally, apply fertilizer 2-3 days after mowing. This allows time for leaf tips to recover while supplying nutrients to expanded leaf surface area.
  • If fertilizing on the same day as mowing, wait at least 8 hours to allow grass blades time to rehydrate before applying fertilizer.

Proper timing prevents fertilizer from contacting cut leaf tips while ensuring sufficient foliar uptake. Leave a gap of at least a few days around mowing to fertilize St. Augustine effectively.

What happens if you don’t fertilize St. Augustine grass?

Neglecting fertilization will cause St. Augustine grass to gradually thin out and lose its lush green color over time. Deficiencies in nutrients like nitrogen, iron, and potassium will emerge.

Visible symptoms like chlorosis, or yellowing, will develop as nutrients are depleted from the soil without being replenished. Growth slows without nutrients to fuel plant processes.

St. Augustine will become more susceptible to weed encroachment due to reduced density and vigor. Bare spots expand as the grass loses its robust spreading ability.

Overall, the turf will lose its vibrant appearance and resilience. Regular fertilization prevents nutrient deficiencies for optimal color, growth, and thickness.

Is too much fertilizer bad for St. Augustine?

Over-fertilizing St. Augustine with excess nitrogen leads to foliar growth surges, requiring frequent mowing. Excessive top growth leaves St. Augustine prone to disease and makes it dependent on extra water.

Applying too much nitrogen can burn leaf tips and roots. Phosphorus accumulation can also trigger iron deficiencies which cause further yellowing.

The best practice is to apply moderate amounts of balanced, slow-release fertilizer. This nourishes St. Augustine gradually without pushing excessive growth. More is not always better.


If you want your St. Augustine lawn to maintain that lush, emerald green color and thick, resilient texture, proper fertilization is essential. By understanding St. Augustine’s nutritional needs and applying fertilizer at the right times, you can fuel robust growth all season long.

Feed in early spring once soils warm to kickstart vegetative expansion. Continue applying balanced, slow-release fertilizer about every 6-8 weeks through summer and into early fall. Reduce nitrogen for late season applications to avoid lush growth prone to winter damage. Even dormant lawns benefit from occasional winter nutrients.

With the fertilizing insights provided in this article, you can confidently nourish your St. Augustine properly throughout the growing season. Tailor your feeding schedule and rates to your grass’s needs based on the season. Proper fertilization will keep your lawn looking its best all year long while avoiding issues like overgrowth and burning. Maintain your emerald carpet with the right fertilizer applied at just the right times!

Scroll to Top