When To Fertilize St. Augustine Grass In Southern California

April 26, 2022 ● Lawn Care

When it comes to fertilizing your St. Augustine grass, timing is everything! Fertilize too early, and you may damage the lawn; fertilize too late, and you won’t see the desired results. So, when is the best time to fertilize your St. Augustine grass in Southern California

Keep reading to find out!

Key Takeaways

  • St. Augustine grass is a warm-season grass that benefits from regular fertilizing in the late spring and summer months. 
  • To avoid fertilizer burn, don’t fertilize when temperatures are sweltering or before the weather has warmed up in the early spring.
  • Make regular mowing, watering, disease control, and insect control part of your fertilizer routine. 

What is St. Augustine Grass?

A popular turfgrass, St. Augustine grass, is commonly grown in the southeastern United States and Southern California.

Along with Bermuda grasses and zoysiagrass, it is one of the most common warm season turfgrasses that you can grow. 

It tolerates modest amounts of shade but grows poorly in heavy shade. It can also thrive in full sun! 

Where it is well-adapted, it absorbs water efficiently and has minimal pest problems. Because of this, it is often used in the moderate California climate zones, like the coastal valleys and southern California. 

It grows rapidly during the summer months, slowing as it enters dormancy in the late fall and winter months. You may notice a brown patch here or there at that time unless your lawn is overseeded with cool season grass types like tall fescue. It has poor cold tolerance, though it can easily handle drought and even salt. 

Features of St. Augustine Grass

You can view key features of this grass type in the table below:

St. Augustine Grass Features

Color Varies, usually dark green
Blade Width 8-9 mm
Texture Coarse
Shade Tolerancer High
Mowing Height 2-4”
Wear Tolerance Mediums
Drought Tolerance Moderate
Soil Preference Loamy, sandy
Salt Tolerance High


St. Augustine grass is one of the tougher residential sod grasses, but not the toughest of sods in general. Because of this, it is often used on lawns and general-purpose areas, but not so much for high-traffic areas like golf courses or sports fields.

This medium-green grass has broad blades with leaves that fold in the blood. It has a creeping growth habit, forming a dense turf, when cared for properly.

When it is healthy, St. Augustine grass can choke out weeds and resist strain. It can be planted by sod or plugs, but one thing that all lawns of this grass type have in common is that they require regular fertilization.

Of course, you also have to get the timing right. Keep reading to learn more!

Best Time to Fertilize St. Augustine Grass

There are a few times each year when fertilizing St. Augustine grass is a good idea. This turfgrass requires a relatively high amount of nitrogen each year. 

The first step in fertilizing your lawn should always be to see what it needs. Test your soil in the late winter or early spring. This will give you a good idea of what sort of fertilizers your lawn needs. Don’t apply a high nitrogen fertilizer during this time. 

If you encourage turfgrass growth in the early spring and then have a freak frost, it can cause damage to your yard.

You can fertilize for the first time in the late spring or early summer months. You’ll use around 2-4 lbs of actual nitrogen per growing season per 1000 square feet of turf. If your soil is sandy, you may use fertilizer at a higher rate, but if it’s clay, you may use less. 

Fertilize three times during the summer unless your soil is composed of heavy clay. The best fertilizer to use will be an all-purpose or complete product formulated for use on a warm-season grass type, which is what your St. Augustine lawn is.

If the temperature gets extremely hot – over 95 degrees – try not to apply too much fertilizer. The high heat can stress your plants, especially if there’s too little water as well. Wait until it cools down. 

Generally, you should stop applying nitrogen fertilizers from September through December into the year’s cooler months. If a soil test indicates that you need to do so, you can still apply potassium to enhance winter hardiness – or lime or sulfur to address an imbalance pH – after cold temperatures have arrived.  

Maintaining St Augustine Grass

Here are some other tips to help you keep your St. Augustine grass a healthy dark green color – no brown spots here!

Watering and Mowing 

When you first seed St. Augustine grass, water deeply to keep the topsoil moist to three inches. 

After it has established itself, you can water one to three times per week, depending on how much rainfall you receive. 

During winter dormancy, you shouldn’t need to water much at all. Remember sandy soil requires more frequent watering than clay – so you may need to adjust accordingly. Water early in the morning to ensure that the maximum moisture gets to the grass roots and doesn’t evaporate off. 

Use a lawnmower that has sharp blades to mow. Dull blades will inflict more stress on your lawn. Mow about once every ten days, keeping the grass as high as possible. This will help it resist weeds and pests. You can get more “bang for your buck” by leaving grass clippings on the lawn, which will provide an extra dose of nutrients.

Weed Control 

St. Augustine develops minimal weeds when taken care of properly. For best results, make sure to control weeds and pests. These reduce the health and appearance of your lawn, stressing the grass and making your fertilizer less effective. Remove weeds by hand or use a pre-emergent herbicide that’s St Augustine-specific. 

Thatch Removal

Thatch is a major problem for St. Augustine grass, as it is for many other grass types. It needs to be dethatched regularly, or it will be difficult to mow.

Not only that but failing to remove thatch may make your lawn more susceptible to diseases and pests (like the infamous chinch bug and mole crickets!). Plus, your efforts with the fertilizer spreader will be less effective since it will be harder for the nutrients to get where they need to go. 

The Bottom Line 

Fertilizing your Saint Augustine grass at the right time can make all the difference in how well it grows and how lush it appears. 

By considering when to fertilize this type of grass, you can help ensure that it looks great all year long.