When To Fertilize Lawn In San Antonio

Knowing when to fertilize lawn in San Antonio is the key to a healthy, green yard that can handle our unique climate. Getting the timing right makes all the difference between struggling grass and a thriving turf.

Our weather here in San Antonio presents specific challenges. We have long, hot summers and usually mild winters, with soil that’s often alkaline and clay-heavy. This means your lawn’s feeding schedule needs to be tailored to our local conditions, not a generic national calendar. Let’s break down the best plan for your grass.

For most San Antonio lawns, the golden rule is to fertilize in late spring and again in early fall. The core growing season for our warm-season grasses is from April through October, and feeding should support this active growth.

Here’s a simple annual schedule to follow:

Late April to Early May (First Application): This kick-starts growth as soil temperatures consistently reach 65°F. It helps your lawn green up and build strength before the summer heat peaks.
Early June (Optional Second Application): If your lawn needs a mid-summer boost, a light feeding can be applied. Avoid heavy nitrogen in peak July/August heat, as it can stress the grass.
September to Early October (Most Important Application): This fall feeding is crucial. It helps recover from summer stress and builds root reserves for the winter, leading to a quicker green-up next spring.

Never fertilize right before a forecasted heatwave or when the lawn is dormant and brown in winter. It’s a waste of product and can harm the environment.

Understanding Your Grass Type

The ideal timing can shift slightly depending on what type of grass you have growing. Most San Antonio lawns are one of these common warm-season varieties.

St. Augustine: This is the most popular lawn grass here. It thrives with the schedule above. It’s important to feed it well in fall to ensure it survives winter and resists brown patch fungus.
Bermuda: Bermuda grass can be fertilized a little more frequently, starting in early May. It handles summer heat well but still benefits massively from the crucial early fall feeding.
Zoysia: Zoysia has a slightly shorter growing season. Start fertilizing in mid to late May and ensure the fall application is done by mid-September, as it goes dormant earlier.
Buffalograss: This native grass requires much less fertilizer. One application in late spring is often sufficient, as too much feeding encourages weeds.

How to Choose the Right Fertilizer

Picking a fertilizer isn’t just about grabbing any bag. You need to understand the numbers on the label and what your soil actually needs.

Look for the three-number ratio (N-P-K) on the bag, which stands for Nitrogen, Phosphorus, and Potassium.

Nitrogen (N): Promotes green, leafy growth. This is the most important number for lawn health. Look for a slow-release nitrogen formula, especially for summer applications.
Phosphorus (P): Supports root development. Our San Antonio soils often have adequate phosphorus, so a lower middle number (like 5 or less) is usually fine unless a soil test shows a deficiency.
Potassium (K): Aids in overall plant health and stress tolerance (drought, heat, cold). This is very important for our climate.

A good all-purpose ratio for San Antonio is something like 15-5-10 or 19-5-9. The best practice, however, is to get a soil test. The Texas A&M AgriLife Extension Service offers affordable kits. This tells you exactly what nutrients are lacking in your soil, so you don’t guess or over-apply.

Step-by-Step: How to Apply Fertilizer Correctly

Doing it right ensures your lawn gets the benefit and protects our local waterways.

Mow: Mow your lawn a day or two before you plan to fertilize. Collect the clippings so the fertilizer can reach the soil.
Check Your Spreader: Whether drop or broadcast, calibrate it according to the bag’s settings. This ensures you apply the correct amount. Applying to much is a common mistake.
Apply to Dry Grass: Fertilize when the grass blades are dry to prevent them from sticking and burning.
Water Deeply: After applying, water your lawn thoroughly. This washes the fertilizer granules off the blades and into the soil. About a half-inch of water is perfect.

The Importance of Soil Testing

We mentioned it briefly, but soil testing deserves its own spotlight. Think of it like a blood test for your yard. It removes all the guesswork.

A test will tell you your soil’s pH (acidity/alkalinity). San Antonio soil is often alkaline (high pH), which can lock up nutrients and prevent grass from absorbing them, even if the fertilizer is present. The test report will give specific recommendations on what type and how much fertilizer to use, and if you need to add amendments like sulfur to adjust the pH.

What to Avoid: Common Fertilizing Mistakes

Even with good intentions, it’s easy to make errors. Here are the top mistakes San Antonio homeowners make.

Fertilizing at the Wrong Time: The worst times are mid-summer peak heat and winter dormancy. Both can damage your lawn.
Over-Fertilizing: More is not better. It leads to excessive growth, thatch buildup, increased disease risk, and pollution of groundwater.
Ignoring Soil pH: Applying fertilizer to highly alkaline soil is often ineffective. The grass simply can’t use it.
Not Watering After Application: This can lead to granule burn on the grass blades and uneven nutrient distribution.

Integrating Fertilizing with Overall Lawn Care

Fertilizing doesn’t work in isolation. It’s part of a complete lawn care strategy.

Your mowing, watering, and weed control habits directly effect how well your fertilizer works. For example, mowing at the proper height for your grass type (often higher than you think) encourages deeper roots. Deep, infrequent watering trains roots to grow down, making your lawn more drought-tolerant. A healthy, well-fed lawn is also the best defense against weeds, as thick grass crowds them out.

Consider aerating your lawn every year or two, especially if you have compacted clay soil. This allows air, water, and yes—fertilizer—to reach the root zone more effectively.

FAQ: Your San Antonio Lawn Fertilization Questions

Can I fertilize my lawn in March?
It’s usually too early. Wait until soil temperatures are reliably warm, typically late April. Fertilizing to early can encourage tender growth that a late frost might damage.

Is it okay to fertilize in the summer?
A light application in early June is okay, but avoid heavy feeding in July and August. The extreme heat stresses the grass, and adding fertilizer can worsen that stress and increase water demands.

When should I do my last fertilization of the year?
Aim for September to early October. This gives the grass time to absorb nutrients and strengthen roots before winter dormancy. Never fertilize after mid-October.

How often should I fertilize St. Augustine grass?
Twice a year is sufficient for most lawns: late spring and early fall. If it looks pale in mid-summer, an extra light feeding can help, but focus on the fall application.

What’s the best fertilizer for San Antonio lawns?
There’s no single “best” product. A balanced, slow-release formula with an N-P-K ratio like 15-5-10 is a safe bet. A soil test will tell you the absolut best choice for your specific yard.

Should I fertilize before or after rain?
Avoid applying right before a heavy downpour, as it can wash the fertilizer away into storm drains. If light rain is expected, it’s generally fine. The ideal method is to apply to dry grass and then water it in yourself.

By following this local guide, you can create a fertilizing schedule that works with San Antonio’s climate, not against it. The result is a lawn that’s healthier, more resilient, and beautifully green throughout the growing season. Remember, consistency with your late spring and early fall feedings, combined with a soil test every few years, sets the foundation for long-term success.