Texas lawns have a specific feeding schedule that aligns with their warm-season growth cycles, so knowing when to fertilize st augustine grass in texas is the difference between a thick, green carpet and a patchy, weed-filled yard. St. Augustine grass thrives in the heat, but it needs the right nutrients at the right time to build strong roots and survive our brutal summers. If you feed it too early or too late, you will waste money and possibly damage the turf.
This guide breaks down the exact months, the best fertilizer blends, and the simple signs your lawn gives you when it is hungry. We will skip the fluff and give you a straight schedule you can mark on your calendar today.
Why Timing Matters For St. Augustine
St. Augustine is a warm-season grass, meaning it does most of its growing when soil temperatures are between 80°F and 95°F. In Texas, that window usually opens in late March or early April and closes around late September. Fertilizing outside that window is not just useless; it can encourage tender growth that gets killed by a late frost or an early cold snap.
Also, over-fertilizing in the fall leads to a condition called “large patch” disease, which shows up as big, rotting circles in your lawn during the winter. The key is to feed the grass when it can actually use the nitrogen, not when it is trying to go dormant.
When To Fertilize St Augustine Grass In Texas
The core schedule for Texas is simple: three to four feedings between spring and late summer. You should not fertilize after September 15th in most parts of the state. Here is the breakdown by region and month.
Early Spring (March To April)
This is your first feeding of the year. Wait until the lawn has greened up at least 50% and you have mowed it twice. If you put down fertilizer too early, the grass roots are not active enough to absorb it, and the nitrogen will just wash away or feed the weeds.
- Use a fertilizer with a ratio like 15-5-10 or 20-0-5.
- Apply at a rate of 1 pound of nitrogen per 1,000 square feet.
- Do this only after the last freeze date for your zip code.
In Houston or Dallas, that is usually mid-March. In Amarillo or Lubbock, you might wait until mid-April. Check the soil temperature; if it is below 65°F, hold off.
Late Spring (May To June)
This is the most important feeding of the year. The grass is growing fast, and it needs a steady supply of nitrogen to build density. This is also the time to add a pre-emergent herbicide if you are using a weed-and-feed product, but be careful with that combo.
Do not use a weed-and-feed in May if you are planning to overseed, but for pure St. Augustine, it is fine. Use a slow-release nitrogen source so the feeding lasts for 8 to 10 weeks.
Mid-Summer (July To August)
Texas summers are scorching. If you have irrigation, you can do a light feeding in July. If you do not water regularly, skip this one. Fertilizing a drought-stressed lawn is like giving coffee to a dehydrated person; it makes things worse.
If you do feed, cut the rate in half. Use a product with higher potassium (the last number) to help the grass handle heat stress. A ratio like 15-0-15 works well here.
Early Fall (September)
You can do one final light feeding in early September, but only if you live in South Texas (San Antonio, Corpus Christi, Houston). For North Texas, skip the fall feeding entirely. The grass is slowing down, and you want it to harden off for winter, not push new blades.
If you must feed in September, use a low-nitrogen, high-potassium formula like 5-0-20. This helps root growth without forcing top growth.
How To Read Your Fertilizer Bag
Fertilizer bags have three numbers, like 18-6-12. The first number is nitrogen (N), which makes the grass green and grow. The second is phosphorus (P), which helps roots. The third is potassium (K), which builds disease resistance and drought tolerance.
For St. Augustine in Texas, you want a ratio where the first number is highest, and the last number is at least half of the first. Avoid high-phosphorus fertilizers unless a soil test says you need it. Texas clay soil already has plenty of phosphorus, and adding more pollutes our waterways.
Slow Release Vs. Quick Release
Always choose a slow-release or controlled-release nitrogen source. Look for the words “polymer-coated” or “sulfur-coated” on the bag. Quick-release nitrogen gives a fast green-up but causes a growth spike that requires frequent mowing and can burn the grass in the summer heat.
Slow-release feeds the lawn steadily for 6 to 8 weeks, which matches the St. Augustine growth cycle perfectly. It also reduces the risk of fertilizer burn on those 100-degree days.
Signs Your Lawn Needs Fertilizer
You do not have to guess. The grass tells you when it is hungry. Look for these signs about 4 weeks after your last feeding.
- Color: The blades turn a pale yellow-green, not a deep emerald.
- Growth: The lawn stops growing, and you only mow every 10 days instead of every 5.
- Thinning: You can see bare soil between the stolons.
- Weeds: Crabgrass and dandelions start popping up, which means the turf is weak.
If you see these signs, it is safe to apply a light feeding as long as you are still within the March-to-September window.
How Much Fertilizer To Apply
Do not guess. Measure your lawn first. The average Texas yard is about 5,000 to 7,000 square feet, but you should calculate it exactly. Use a measuring wheel or a simple online map tool.
- Measure the length and width of your lawn in feet.
- Multiply them to get square footage.
- Subtract areas covered by the house, driveway, and flower beds.
Once you know the square footage, read the bag. Most fertilizers are designed to apply 1 pound of nitrogen per 1,000 square feet. If your lawn is 5,000 square feet, you need 5 pounds of nitrogen. If the bag is 18% nitrogen, you divide 5 by 0.18, which means you need about 28 pounds of the product.
Using A Spreader Correctly
Set your drop spreader or broadcast spreader to the setting listed on the bag. Then, apply in a crisscross pattern. Go north-south first, then east-west. This prevents stripes and ensures even coverage. Overlap slightly to avoid gaps, but do not double-apply in one spot.
Water the fertilizer in immediately after application. St. Augustine needs about 0.5 inches of water to push the nutrients into the soil. If you do not water, the nitrogen can volatilize into the air and be lost.
Common Fertilizing Mistakes In Texas
Even experienced homeowners make these errors. Avoid them to keep your lawn healthy.
- Fertilizing before the last frost: This kills new growth and wastes money.
- Using high-phosphorus fertilizer: This causes runoff and does not help St. Augustine.
- Applying on wet grass: The granules stick to the blades and burn them.
- Skipping the soil test: You might have high potassium already, so you are just wasting money.
- Feeding in October: This encourages winter kill and large patch disease.
Organic Options For St. Augustine
If you prefer not to use synthetic chemicals, you can use compost or organic granular fertilizers. These release nutrients slowly and improve soil structure. Apply a 0.5-inch layer of compost in the spring and again in late summer. This is a great top dressing that feeds the soil microbes, which in turn feed the grass.
Organic fertilizers like milorganite or composted chicken litter work well. They have lower nitrogen content, so you need to apply more product, but they are harder to burn the lawn with. Just remember that organics are slower to show results, so be patient.
Fertilizing New Sod Vs. Established Lawns
Newly laid St. Augustine sod has different needs. Do not fertilize it for the first 30 days. The roots are trying to knit into the soil, and fertilizer can burn the tender new stolons. After 30 days, use a starter fertilizer with a higher middle number (phosphorus) to encourage rooting, but only if a soil test says you need it.
Established lawns (older than one year) follow the standard schedule above. If you have a lawn that is 5 years old or older, you can often skip the spring feeding entirely if you leave the grass clippings on the lawn. The clippings recycle nitrogen back into the soil.
Watering And Fertilizer Go Hand In Hand
You cannot fertilize a dry lawn. St. Augustine needs about 1 to 1.5 inches of water per week during the growing season. If you are not watering, the fertilizer sits on the surface and either washes away or burns the roots. Always water deeply and infrequently, rather than a little bit every day.
Set your sprinklers to run early in the morning, around 4 AM to 6 AM. This gives the water time to soak in before the sun evaporates it. It also reduces the risk of fungal diseases, which love wet grass at night.
Soil Testing Is The Smart Move
Before you buy any fertilizer, spend $15 on a soil test from Texas A&M AgriLife Extension. They will tell you exactly what your soil lacks. You might find that you have plenty of phosphorus and potassium, so you only need a nitrogen-only fertilizer like 21-0-0. This saves money and prevents over-application.
You can get a soil test kit from your county extension office or order one online. Take samples from 4 to 6 different spots in your lawn, mix them together, and send them off. Results come back in about two weeks.
Frequently Asked Questions
Can I fertilize St. Augustine grass in October in Texas?
No, you should avoid fertilizing after mid-September in most of Texas. Late feeding encourages new growth that will be killed by the first frost, and it increases the risk of large patch disease. Stop feeding by Labor Day for North Texas and by October 1st for South Texas.
What is the best fertilizer for St. Augustine grass in Texas?
Look for a slow-release fertilizer with a 3-1-2 or 4-1-2 ratio, like 15-5-10 or 16-4-8. Make sure the nitrogen is slow-release and the potassium is at least half the nitrogen amount. Avoid high-phosphorus blends unless a soil test shows a deficiency.
Should I fertilize St. Augustine grass in the summer?
Yes, but only if you are watering regularly. In July and August, use a light application at half the normal rate. If your lawn is dormant or brown due to drought, do not fertilize at all. Wait until the grass recovers and starts growing again.
How often should I fertilize St. Augustine grass?
Three to four times per year is enough. Once in early spring, once in late spring, once in mid-summer (optional), and once in early fall (only for South Texas). Over-fertilizing leads to thatch buildup and disease.
Can I use weed-and-feed on St. Augustine?
Yes, but be careful. Many weed-and-feed products contain herbicides that can damage St. Augustine, especially in the heat. Look for products specifically labeled for St. Augustine, and do not apply them when temperatures exceed 85°F. Also, do not use them in the fall.
Final Feeding Schedule For Texas
Here is a quick cheat sheet you can save for next year. Adjust the dates based on your local weather, but use this as a baseline.
- March 15 to April 15: First feeding, 1 lb N per 1k sq ft.
- May 15 to June 15: Second feeding, 1 lb N per 1k sq ft.
- July 15 to August 15: Optional light feeding, 0.5 lb N per 1k sq ft.
- September 1 to September 15: Only for South Texas, low-N formula.
Stick to this schedule, water properly, and mow at 3.5 to 4 inches, and your St. Augustine will be the envy of the neighborhood. The grass is forgiving, but it is not invincible. Feed it right, feed it on time, and it will reward you with a thick, lush lawn that handles Texas heat like a champion.
Remember to always read the label on your fertilizer bag, because local regulations and product formulations can vary. And if you are ever unsure, a simple soil test takes the guesswork out of the equation. Your lawn does not need a lot, it just needs the right thing at the right time.