A favorite in warm coastal regions due to its ability to tolerate salt, high humidity, and toasty temperatures, St. Augustine grass (Stenotaphrum secundatum) is widely grown in Hawaii, Florida, the Gulf states, and elsewhere in USDA growing zones 8 through 10.
St. Augustine grass thrives in well-drained soil and imparts an appealing blue-green tone to lawns. Although it prefers sunny areas, it tolerates a bit of shade. While this vining-type grass spreads rapidly, it can grow a bit spindly if the soil doesn’t have adequate nutrients, which is the case with a lot of sandy soils in the coastal states.
To reach its full, lush potential, St. Augustine grass should be fertilized during the summer growing season. Ahead, learn what to look for when choosing the best fertilizer for St. Augustine grass, and find out why the following lawn fertilizers are top performers.
- BEST OVERALL: Scotts Southern Turf Builder Lawn Food
- BEST BANG FOR THE BUCK: Pennington 100536576 UltraGreen Lawn Fertilizer
- BEST WITH SPRAYER: Simple Lawn Solutions Commercial Grade Lawn Energizer
- BEST LIQUID: Simple Lawn Solutions Maximum Green Liquid Fertilizer
- BEST NATURAL: Milorganite 0636 Organic Nitrogen Fertilizer
- BEST SOD STARTER: Pennington UltraGreen Starter Lawn Fertilizer, 14 LBS
What to Consider When Choosing the Best Fertilizer for St. Augustine Grass
Fertilizing adds essential nutrients to soil that plants need to thrive. The first step in choosing a fertilizer for St. Augustine grass is to have the soil tested to determine whether it lacks specific nutrients. Most communities have county extension agencies that will test the soil’s nutrient content.
Once you know which nutrients, if any, are lacking in your soil, you’re in a better position to select an optimal lawn fertilizer. By and large, St. Augustine grass will benefit from the same fertilizers used on other types of lawn.
Lawn and turf fertilizers are labeled with the amounts, by weight, of three specific nutrients they contain: Nitrogen (N) brings out the color in the grass and speeds growth, phosphorus (P) encourages bud and seed formation, and potassium (K) encourages healthy plant growth. While all three are required for St. Augustine grass to grow well, the nutrient that soils lack most is nitrogen.
St. Augustine grass usually contains more nitrogen than phosphorus and potassium. A typical turf fertilizer formulation, for example, has an NPK ratio of 15-1-5. As you browse lawn fertilizers, you’ll notice how many different NPK combinations they offer, but nearly all of them are highest in nitrogen.
Liquid vs. Granular vs. Water-Soluble
Lawn fertilizers are made in three main formulations: liquid, granular, and water-soluble. There’s no “right” option here—the form of fertilizer that’s best for your lawn is mostly a matter of personal preference.
- Liquid: For a quick boost of growth, many growers and groundskeepers opt to apply liquid lawn fertilizer because it’s quickly absorbed through the blades of grass and immediately goes to work, encouraging new growth. Results can be seen in as little as 3 or 4 days after applying liquid fertilizer to St. Augustine grass. The product can be purchased either full strength or in a liquid concentrate for diluting and applying via a pump-type garden sprayer. The caveat with liquid fertilizers is that they quickly pass through and out of the lawn, so they may need to be applied more frequently than granular types.
- Granular: Resembling tiny grains, granular fertilizers contain many of the same nutrients that liquid fertilizers contain. They differ slightly in that granular fertilizers are often released more slowly, which means the grass’s roots can access the nutrients over an extended period. Granules won’t give you the same rapid greening-up that liquid fertilizers will, but they typically require less frequent application. Granular fertilizers are applied to the lawn using a spreader.
- Water-Soluble: Though this fertilizer comes in a granular form, it’s not meant to be applied with a spreader. Instead, water-soluble fertilizers are made to be applied using a hose-end dispenser that connects to a garden hose. The water flows through the dispenser, dissolving and diluting the granules and dispersing the fertilizer via a hand-held sprayer. Like liquid fertilizer, water-soluble fertilizer can green up the lawn fairly quickly.
Organic vs. Synthetic
Most lawn fertilizers contain chemical and synthetic ingredients, but a few are made from all natural components.
Organic: Natural organic fertilizers contain the same nutrients as synthetic fertilizers, but they come from natural sources, such as earthworm castings and composted manure. They’re usually more expensive than synthetic formulations because it takes more work to gather the ingredients and process them into fertilizer. The upside is that organic fertilizers are eco-friendly and unlikely to pollute waterways or harm aquatic life.
Synthetic: Chemicals made in a laboratory to mimic the nutrients found in nature are the main components of synthetic fertilizers. Depending on the product, synthetic fertilizers may also be enriched with essential minerals found in healthy soil, such as calcium, magnesium, or boron. While lawns will react to both types of fertilizers favorably, the high nitrogen content in some synthetic fertilizers can harm aquatic life if it runs off in waterways.
Knowing when to fertilize is just as important as using the right fertilizer. St. Augustine grass should be fertilized for the first time in spring only after turning fully green. Fertilizing it before that time may damage the grass. Apply an all-purpose lawn fertilizer that’s high in nitrogen at the rate recommended on the package. After that, St. Augustine grass should be fertilized every 6 to 8 weeks, depending on the product’s recommendations.
St. Augustine grass doesn’t grow well from seed, so it’s usually propagated through sod or plugs. When starting a new lawn of St. Augustine, apply a lawn starter fertilizer that offers a balanced ratio of nutrients, such as 10-10-10, to the ground beneath the sod. As the roots grow downward, the fertilizer will be absorbed and boost plant health.
A high-nitrogen fertilizer can be applied a month later, followed by periodic applications during the growing season. Stop fertilizing in the fall approximately 1 month before outdoor temperatures drop to around 55 degrees Fahrenheit. At this temperature, St. Augustine grass goes dormant, and won’t need any fertilizer until spring.
Our Top Picks
St. Augustine grass looks its best when it gets all the nutrients it needs, which is why periodically applying a general lawn fertilizer will increase the lawn’s lushness—and the chances that you’ll have a uniformly green lawn. Choosing between liquid, granular, and water-soluble is mostly a matter of personal preference. These lawn fertilizers are all suitable for boosting nutrients in a St. Augustine lawn and keeping it looking lush.
To boost and deepen the blue-green color that makes St. Augustine grass so recognizable, consider applying Scotts Southern Turf Builder Lawn Food, which features a nitrogen-rich 32-0-10 NPK formulation. It’s made for Southern yards and helps protect grass from drought and heat. Scotts’ turf-building formulation is composed of all-in-one particles that evenly distribute the nutrients necessary to improve the grass’s health, boost its color, and protect it from hot temperatures.
This granulated fertilizer feeds lawns up to 10,000 square feet and can be applied with either a drop or a broadcast spreader. For best results, follow the application rate on the bag and water the lawn after applying it. Or, save water by applying the product within 48 hours of when rain is forecast.
For those looking for a reasonably priced fertilizer with widespread coverage, consider Pennington UltraGreen Lawn Fertilizer. It features a high-nitrogen 30-0-4 NPK ratio, designed to boost robust growth and rich color in St. Augustine lawns. A 14-pound bag of UltraGreen fertilizer covers up to 5,000 square feet and can be applied by a drop spreader or a broadcast spreader.
The product features slow-release nitrogen that continues feeding the lawn for up to 3 months after it’s applied, so users may not need to fertilize as often. UltraGreen helps protect the grass from heat and drought and contains 5 percent iron to deepen the blue-green color of St. Augustine turf
No spreader? No problem. With Simple Lawn Solutions’ Lawn Energizer, buyers receive a 32-ounce jug with a built-in sprayer that attaches to a garden hose, making it simple to fertilize the lawn without buying a spreader or a pump sprayer. Lawn Energizer comes in a concentrated liquid that feeds an area up to 3,200 square feet—refill jugs are also available.
The fertilizer features a nitrogen-rich 6-0-0 NPK ratio to deepen and enrich St. Augustine’s blue-green color and encourage dense growth. Iron and micronutrients in Lawn Energizer’s formulation improve soil quality and promote healthy root development.
Another product from Simple Lawn Solutions among these top picks, Maximum Green provides a high-nitrogen NPK formulation of 28-0-0 to boost lawn color and encourage robust growth quickly. Maximum Green is worth considering in that it contains 70 percent quick-release nutrients and 30 percent slow-release nutrients.
After providing a quick burst of growth and color, the fertilizer will slowly release a steady supply of nutrients, which may mean users can wait longer between feedings. Like many Simple Lawn Solutions liquid products, Maximum Green comes in its own 32-ounce sprayer jug that attaches to a garden hose for easy feeding.
This product has no chemicals at all. Milorganite’s Organic Natural Fertilizer provides a gentle nitrogen boost to add color to St. Augustine grass while increasing the density of the lawn, and it does so without any synthetic ingredients. This organic fertilizer is made from composted manure and it offers a beneficial 6-4-0 NPK formulation.
Milorganite comes in a 32-pound bag of granules that can be applied with a drop spreader or a broadcast spreader, and a single bag will feed up to 2,500 square feet of lawn. This all-natural fertilizer will improve soil health, and it’s safe for the environment—users need not worry about runoff polluting waterways or harming aquatic life.
Regular lawn fertilizers don’t always contain enough phosphorus to help start a new lawn of St. Augustine grass from sod, which is the preferable way of growing this grass species. Pennington UltraGreen Starter lawn fertilizer provides an optimal 22-23-4 NPK ratio to encourage root development in a new sod lawn.
This granular starter fertilizer comes in a 14-pound bag and treats up to 5,000 square feet. For best results, apply this Pennington product with a drop spreader or a broadcast spreader to the soil before laying the sod strips. When the sod is in place, water well to help establish the new grass. If inserting St. Augustine plugs into an existing lawn, applying UltraGreen starter will encourage healthy root development.
FAQs About Your New Fertilizer for St. Augustine Grass
St. Augustine lawns are typical in warm coastal states but will grow anywhere in USDA zones 8 through 10. For a healthy, uniformly colored lawn, apply a good turf fertilizer regularly. Those who are new to growing St. Augustine grass will likely have some questions.
Q. When should St. Augustine grass be fertilized?
The first feeding in the spring should take place a week or two after the grass has entirely greened up. After that the frequency with which you apply fertilizer depends on the product’s strength, so follow package directions. In general, every 4 to 6 weeks is usually sufficient.
Q. Is it possible to overfertilize St. Augustine grass?
Applying fertilizer at a rate that exceeds the recommended rate, or applying it more often than is recommended, can result in faster grass blade growth but not necessarily healthier grass. It will, however, result in more frequent mowing.
Q. How is fertilizer applied to a lawn?
The most efficient way to distribute fertilizer is to use a pump-type sprayer for liquids, and a spreader to apply granulated products. For water-soluble fertilizer, use a hose-end dispenser.
Q. Can fertilizer be applied to wet grass?
Yes. The caveat here is to wait until after heavy rain if water is still running off the lawn, which could result in the fertilizer washing away.
Q. Should turf or sod be watered after fertilizing?
When applying a liquid fertilizer—no. Granulated fertilizers may call for watering after application or using the product a day or two before rain is expected.