When To Fertilize St Augustine Grass In Texas

Knowing when to fertilize St Augustine grass in Texas is the single most important factor for a thick, green lawn. Get the timing wrong, and you risk weak growth, disease, or even damaging your turf. This guide cuts through the confusion to give you a clear, regional schedule for optimal results.

Texas is a big state with varied climates, so a one-size-fits-all approach doesn’t work. Your fertilization schedule depends heavily on whether you’re in North Texas, Central Texas, or the Gulf Coast region. We’ll break it down by area and season, giving you the exact steps to follow.

Your fertilization calendar revolves around soil temperature, not just the date on a calendar. St Augustine grass begins actively growing when soil temperatures consistently reach 65°F. It goes dormant and stops growing when soil temperatures fall below 55°F. Fertilizing outside these active growth windows is wasteful and can harm the grass.

Understanding the Texas Growing Seasons

Texas lawns have two main growth spurts: late spring/summer and early fall. The goal is to feed the grass just before these peaks.

Spring Green-Up: This is when your grass wakes from winter dormancy. Fertilizing too early can force tender growth that a late frost might damage.
Summer Vigor: This is the main growing season. Proper feeding here builds a strong root system and dense turf to crowd out weeds.
Fall Preparation: A final, timely feeding helps the grass store energy in its roots for winter survival and a faster spring green-up.

The Regional Fertilization Schedule

Here’s where we tailor the plan. Follow the guide for your region of Texas.

North Texas (Dallas-Fort Worth, Lubbock, Amarillo)

This region has colder winters and a shorter growing season. You’ll typically apply fertilizer 3-4 times per year.

First Application (Spring): Apply a nitrogen-rich fertilizer in late April to mid-May. Wait until all danger of frost has passed and the grass is fully green and actively being mowed.
Summer Application(s): Apply a second feeding in early to mid-June. If needed, a third light application can be made in early July. Avoid fertilizing in the peak heat of late July and August.
Final Application (Fall): Apply a winterizer fertilizer (higher in potassium) in early to mid-September. This is crucial for winter hardiness in the north.

Central Texas (Austin, San Antonio, Waco)

With milder winters and longer summers, Central Texas lawns benefit from a 4-5 step program.

First Application (Spring): Target mid to late April. The soil warms up a bit earlier here than in the north.
Summer Applications: Follow up in late May or early June, and again in early July. A fourth application can be made in early August if the lawn shows signs of hunger (pale color, slow growth), but be cautious and use a lighter rate.
Final Application (Fall): Apply your fall fertilizer by mid to late September. This gives the grass plenty of time to absorb nutrients before growth slows.

Gulf Coast & South Texas (Houston, Corpus Christi, Brownsville)

This region has a very long growing season and often struggles with high humidity and disease pressure. A consistent 4-5 application schedule is key.

First Application (Spring): You can start a bit earlier, in early to mid-April.
Summer Applications: Fertilize in late May, early July, and mid-August. Spacing applications about 6-8 weeks apart is effective.
Final Application (Fall): Apply your last feeding in late September or even early October. Growth continues longer here due to warm soil.

Choosing the Right Fertilizer

Not all lawn fertilizers are created equal. For St Augustine grass in Texas, you need to look at the three numbers on the bag (N-P-K).

Nitrogen (N): The first number. This is most important for green, leafy growth. Look for a fertilizer where the first number is the highest, like a 15-5-10 or 20-5-10 blend.
Phosphorus (P): The second number. Supports root development. Many Texas soils already have adequate phosphorus, so a lower middle number is often fine. A soil test can tell you for sure.
Potassium (K): The third number. This is the “stress” nutrient, vital for drought tolerance, disease resistance, and winter hardiness. It’s especially important in your fall fertilizer.

For most of the season, a balanced, slow-release nitrogen fertilizer is ideal. It feeds the grass gradually over 6-8 weeks, preventing a surge of weak growth and reducing the risk of burning the lawn. Your fall application should be a specific “winterizer” formula or a fertilizer with a higher last number (e.g., 5-10-30).

Step-by-Step Fertilizer Application

Doing it right ensures even coverage and prevents problems.

Mow First: Mow your lawn at your regular height (3-4 inches for St Augustine) and bag the clippings to ensure the granules reach the soil.
Check the Spreader: Use a broadcast (rotary) spreader for large areas. Calibrate it to the setting recommended on your fertilizer bag to avoid over or under-applying.
Apply Evenly: Walk at a steady pace, slightly overlapping each pass to prevent striping. Going over the lawn twice in a crosshatch pattern (north-south, then east-west) guarantees great coverage.
Water Deeply: Immediately after applying, water the lawn thoroughly. This washes the fertilizer off the grass blades and into the soil, where the roots can access it. This step also prevents burning.

Critical Mistakes to Avoid

Even with good timing, these errors can set your lawn back.

Fertilizing Too Early in Spring: This is the most common error. It wastes money and can promote weed growth or cold damage.
Fertilizing in Drought or Dormancy: Never fertilize a brown, dormant lawn during a summer drought or in winter. The grass cannot use the nutrients, and salts can build up and damage the roots.
Over-Fertilizing: More is not better. Excess nitrogen leads to rapid, weak growth that is more suceptible to disease (like brown patch), insect damage, and thatch buildup. It also pollutes waterways.
Skipping the 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 Other Lawn Care Practices

Fertilizer works best when combined with proper overall care.

Watering: St Augustine needs about 1 inch of water per week, including rainfall. Water deeply and infrequently early in the morning to encourage deep roots and prevent fungus.
Mowing: Keep your mower blade sharp and never cut more than 1/3 of the grass blade height at once. Mowing too short scalps the lawn, stressing it and allowing weeds to invade.
Aeration: If your soil is compacted, core aerate in late spring or early summer. This allows air, water, and your fertilizer to reach the root zone more effectively.

FAQ: Your Texas St Augustine Fertilizer Questions

Can I fertilize St Augustine grass in October?

It depends on your region. In North Texas, October is too late; aim for September. In Central Texas, early October might be okay for a late fall feeding. In South Texas, October is often the perfect time for the final application. The rule is to fertilize about 6-8 weeks before the first expected frost.

What is the best winter fertilizer for St Augustine?

Look for a product labeled as a “winterizer” or one with a low first number and a high last number (like 5-10-30 or 0-0-20). The high potassium (K) content strengthens cell walls and improves the grass’s tolerance to cold and disease over the winter months.

Should I fertilize after rain?

Yes, this can be a good time. Just ensure the grass blades are dry before application so the fertilizer doesn’t stick to them and cause burning. Also, avoid applying if heavy rain is forecasted immediately after, as it can wash the fertilizer away before it soaks in.

Is it too late to fertilize in September?

September is prime time for the fall fertilizer application across most of Texas. In fact, it’s the most important feeding for many areas. As long as your grass is still green and growing, applying a winterizer fertilizer in September is highly recommended.

How often should you really fertilize St Augustine?

A general rule is every 6-8 weeks during the active growing season. For most Texas lawns, this translates to 4 times a year: spring, early summer, late summer, and fall. Over-fertilizing is a bigger problem than under-fertilizing for this grass type, so stick to the schedule.

Following this Texas-specific guide for when to fertilize your St Augustine grass will give you a significant advantage. By syncing your lawn care with the natural growth cycles in your region, you provide exactly what the grass needs exactly when it needs it. The result is a resilient, beautiful lawn that can better handle the Texas heat, cold, and everything in between. Remember, consistency with proper mowing and watering is just as important as the fertilizer itself for achieving that optimal growth you’re after.