When To Fertilize St Augustine Grass In Florida

Knowing when to fertilize St. Augustine grass in Florida is the single most important factor for a healthy, green lawn. Get the timing wrong, and you risk damaging your turf or feeding the weeds instead. This guide cuts through the confusion to give you the optimal schedule for your region.

Florida’s unique climate, with its long growing season and distinct regions, demands a specific approach. We’ll break down the best times to feed your lawn, what products to use, and how to avoid common mistakes that can set your lawn back.

Your fertilization schedule is dictated by where you live in the state. Florida is broadly divided into three zones: North, Central, and South. Grass growth cycles vary significantly between them, so a one-size-fits-all plan doesn’t work.

Understanding Florida’s Lawn Fertilization Zones

The University of Florida IFAS Extension provides clear zone guidelines. Following these ensures you fertilize during active growth, not during dormancy.

North Florida: This area includes cities like Pensacola, Tallahassee, and Jacksonville. Winters are cooler, and St. Augustine may go fully dormant (brown) after a frost.
Central Florida: This zone covers Orlando, Tampa, Lakeland, and Ocala. It has a longer growing season than the north, with milder winters where the grass often slows but may not fully brown.
South Florida: Encompassing Miami, Fort Lauderdale, West Palm Beach, and the Keys, this region has a year-round growing season. The grass rarely goes dormant, if ever.

The Optimal Fertilization Schedule by Region

Here is the step-by-step, seasonal timing for each zone. Always wait until your lawn is fully green and actively growing after winter before the first application.

North Florida Schedule

First Application: Mid to late April, after the last frost threat has passed and soil temperatures are consistently warm.
Second Application: Early to mid-June.
Third Application: Early to mid-August.
Final Application: Early to mid-October, using a winterizer formula low in nitrogen but higher in potassium.

Do not fertilize after October 15th. This allows the grass to harden off for winter and prevents cold damage.

Central Florida Schedule

First Application: Early to mid-April.
Second Application: Early June.
Third Application: Early August.
Final Application: Late September to early October, with a winterizer.

The cutoff date for fertilization in Central Florida is typically November 1st. Applying to late can promote tender growth that gets hit by an early cold snap.

South Florida Schedule

First Application: Late February to early March.
Second Application: May.
Third Application: July.
Fourth Application: September.

In South Florida, you can sometimes add a fifth, light application in early November if growth is still strong, but it’s often not nessesary. The key is consistent, light feedings through the long season.

Choosing the Right Fertilizer

Using the correct product is as crucial as timing. Look for a slow-release nitrogen fertilizer. This feeds the lawn gradually over 6-8 weeks, preventing a surge of growth that attracts pests and requires constant mowing.

NPK Ratio: A good ratio for St. Augustine is 15-0-15, 16-0-8, or similar. The first number (Nitrogen) promotes green growth. The second (Phosphorus) is often restricted in Florida due to our naturally high soil levels. The third (Potassium) strengthens roots and improves stress tolerance.
“Florida-Friendly” Label: Look for this designation on the bag. It means the product meets state guidelines for slow-release nitrogen and minimal phosphorus.
Winterizer: For your fall application, choose a fertilizer where the last number (Potassium) is equal to or higher than the first (Nitrogen), such as 5-0-10 or 10-0-20.

How to Apply Fertilizer Correctly

Proper technique ensures even feeding and prevents burns.

Mow First: Mow your lawn 1-2 days before you plan to fertilize.
Check the Weather: Apply when no heavy rain is forecasted for 24-48 hours, but you can water it in yourself.
Calibrate Your Spreader: This step is often skipped but vital. Set your broadcast or drop spreader to the rate listed on the fertilizer bag.
Apply Evenly: Overlap your passes slightly to avoid striping. Be careful not to spill product on driveways or sidewalks, as it can runoff into waterways.
Water Deeply: After application, water the lawn thoroughly to wash the granules off the grass blades and into the soil. This prevents burning and activates the fertilizer.

Critical Mistakes to Avoid

Even with good timing, these errors can ruin your lawn’s health.

Fertilizing Too Early in Spring: This feeds winter weeds and can push grass growth before soil is warm enough, leading to weak roots.
Fertilizing in Winter: Fertilizing dormant grass is useless and can pollute groundwater since the grass isn’t growing to use the nutrients.
Using “Weed & Feed” Products Improperly: These combine fertilizer and herbicide. Only use if you have a widespread weed problem, and never during spring green-up or summer heat stress, as they can damage St. Augustine.
Overwatering After Application: Water deeply once to move fertilizer into the soil, then return to your normal watering schedule. Excessive watering leaches nutrients away.
Ignoring a Soil Test: A soil test from your local county extension office is inexpensive and tells you exactly what your soil lacks. It takes the guesswork out of choosing amendments.

Integrating Fertilization with Overall Lawn Care

Fertilizer isn’t a magic fix. It works best as part of a complete lawn care strategy.

Watering

St. Augustine needs about 3/4 to 1 inch of water per week, including rainfall. Water deeply and infrequently to encourage deep root growth. Early morning is the best time to water.

Mowing

Keep your mower blade high. St. Augustine should be mowed at 3.5 to 4 inches tall. Taller grass shades the soil, conserves moisture, and outcompetes weeds. Never remove more than 1/3 of the grass blade in a single mowing.

Insect and Disease Watch

A well-fertilized lawn is more resistant, but watch for signs of chinch bugs (yellowing in sunny areas) or fungal diseases like brown patch. Proper watering and mowing are your first line of defense.

FAQ: Your Florida Fertilization Questions Answered

Q: Can I fertilize St. Augustine grass in the summer?
A: Yes, but carefully. In North and Central Florida, your summer application is crucial. However, avoid fertilizing during periods of extreme drought or heat stress unless you can irrigate sufficiently. South Florida follows its regular summer schedule.

Q: What is the best month to fertilize St. Augustine in Florida?
A: There isn’t one “best” month. The best time is a series of applications. For most, the first application in spring (April) and the fall winterizer (Sept/Oct) are the most important for green-up and cold protection, respectively.

Q: Is it too late to fertilize in October?
A> It depends on your zone. In North Florida, mid-October is the absolute cutoff. In Central Florida, late October is okay. In South Florida, October is a standard feeding month. When in doubt, use a winterizer formula and apply by the middle of the month.

Q: Should I fertilize after laying sod?
A: New sod needs starter fertilizer, which is higher in phosphorus to promote root establishment. Apply this at laying, then wait 6-8 weeks before starting your regular fertilization schedule with a balanced, slow-release product.

Q: Why does my lawn look worse after I fertilize?
A> This could be fertilizer burn from applying to much, not watering it in, or using a quick-release product. It could also be an undiagnosed pest or disease problem that fertilizer won’t fix. Always follow label rates and water deeply after application.

By following this regional schedule and best practices, you’ll provide your St. Augustine lawn with the nutrients it needs exactly when it can use them best. The result is a resilient, beautiful turf that can better withstand Florida’s heat, rain, and occasional chills. Remember, a soil test is your best starting point for a truly perfect lawn program.