Maintaining St. Augustine Grass Lawns

With proper maintenance, you can help keep your St. Augustinegrass lawn healthy and attractive.

St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze) is a popular warm-season turfgrass for home lawns. It is found in the United States, southern Mexico, South America, South Africa, western Africa, the Caribbean, the Hawaiian Islands, Australia and the South Pacific.

St. Augustinegrass is medium to dark green and coarse textured, and it has a low, dense growth habit. It grows well in nearly all soil types and tolerates shade, heat, salt and, to some degree, drought. It does not tolerate waterlogged soils or extended periods of cold weather. St. Augustinegrass is an aggressive species that spreads rapidly by above-ground growth structures called stolons. If managed properly, St. Augustinegrass forms a dense cover that handles light traffic and competes well with most weeds. St. Augustinegrass is the most shade tolerant warm-season turfgrass.

Texas Common, Raleigh, Seville, Palmetto and Floratam are St. Augustine varieties commonly used for home lawns in the southern United States. Each variety has characteristics that make it best in certain situations. Contact your county Extension agent for information on the variety best suited for your location.

To keep your St. Augustinegrass lawn in good condition, follow these guidelines for mowing, watering and fertilizing, as well as for controlling weeds, insects, thatch, and eliminating compacted soil. Because many factors affect turf growth, these are general recommendations to help you avoid common St. Augustine grass problems.

March through May

Mowing

Begin a routine mowing program as soon as the grass begins to turn green in the spring. Remove no more than one-third of the leaf area with any one mowing. Set the mowing height at 2 1/2 to 3 inches (3 to 3 1/2 inches in shady lawns). The lower the mowing height, the more frequently you will need to mow. Frequent mowing at a lower height produces higher quality turfgrass.

It is best not to bag grass clippings. Grass clippings decompose quickly and return significant amounts of nutrients to the soil. If you do bag the clippings, consider composting them for use in the landscape.

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Fertilizing

Begin fertilizing 3 weeks after the grass turns green and when there is little chance of a late frost. Apply 1 pound of soluble nitrogen per 1,000 square feet of lawn every 8 weeks, or 1 1/2 pounds of slow-release nitrogen every 10 weeks.

Have your soil tested to determine what added nutrients your lawn may need. For information on soil testing procedures, contact your county Extension agent. If you do not have the soil tested, use a complete fertilizer with a 3-1-2 ratio of nitrogen, phosphorus and potassium (Examples: 15-5-10, 21-7-14, etc. Every bag of fertilizer has the nutritional analysis printed on the bag).

To determine the amount of fertilizer needed to equal 1 pound of nitrogen per 1,000 square feet, divide 100 by the first number in the fertilizer analysis. For example, if you are using a 15-5-10 fertilizer, then you need 6.6 pounds per 1,000 square feet.
(To determine the amount needed to apply 1 1/2 pounds per 1,000 square feet, substitute 150 for 100.) 100/15 = 6.6

Then determine the size of the area to be fertilized. If your lawn is 5,000 square feet, you will need 33 pounds of 15-5-10 fertilizer.
(5,000 1,000) x 6.6 = 33 pounds of fertilizer

Watering

To keep your lawn healthy, water it only when the grass needs it. When you do water, wet the soil to a depth of 6 inches. Then don’t water again until the grass shows symptoms of drought stress—a dull, bluish color, rolled or folded leaves, and persistent footprints. This usually occurs in 5 to 10 days, depending on the weather.

Follow these steps to determine how long to water to apply the right amount.

  1. Set out five or six open-top cans randomly around the lawn (tuna or cat food cans work best).
  2. Turn on the sprinklers or irrigation system for 30 minutes.
  3. Using a ruler, measure the depth of water caught in each individual can, and record the depths.
  4. Calculate the average depth of water of all the cans.
    Example: You have placed five cans in your yard. The depths of water in the cans were 0.5 inch, 0.4 inch, 0.6 inch, 0.4 inch and 0.6 inch. Add the depths together and divide by the number of cans you used.
    0.5 + 0.4 + 0.6 + 0.4 + 0.6 = 2.5 inches
    2.5 inches
    5 cans = 0.5 inch of water in 30 minutes
    New-style irrigation controllers allow you to water several times a day, so you can program them to prevent run-off.
  5. Use a garden spade or a soil probe to find out how deeply the soil was wet during the 30-minute period. The probe will push through wet soil easily, but it is more difficult to push through dry soil.
  6. When you know how much water was applied in 30 minutes and how deeply that volume of water wet the soil, then determine how long you must water to wet the soil to a depth of 6 inches.
    Example: If the sprinklers sprayed 1/2 inch of water in 30 minutes and wet the soil to a depth of 3 inches, you would need to apply 1 inch of water to wet the soil to a depth of 6 inches. To do so you must water for 1 hour. Run-off from watering a lawn can waste a significant amount of water, which is costly and a poor use of a limited natural resource. The factors determining how quickly run-off occurs are the type of soil and the application rate of the sprinkler system. Do not apply water faster than the soil can absorb it.

To prevent run-off:

  1. Check the lawn while watering. If water begins running into the streets or gutters, note how long it took before run-off occurred. This is the maximum amount of time you should water at one time.
  2. Stop watering and allow the soil surface to dry (30 minutes to 1 hour).
  3. Begin watering again and continue for the time you’ve determined. With an automatic irrigation system, change your timer to the new, shorter time.
  4. Continue this cycle until the appropriate amount of water has been applied to wet the soil to a depth of 6 inches.

Controlling weeds

The best form of weed control is a healthy, dense, actively growing lawn. To control crabgrass and other grassy weeds, apply preemergent herbicides (which control weeds before they sprout from the ground) in the spring when soil temperature reaches 65 ºF or when the redbud and dogwood trees begin to bloom. Apply postemergent herbicides (which control weeds that have already sprouted) as needed. Apply herbicides only when weeds are present, and when the grass is healthy and actively growing.

Weed control is most effective if you apply the herbicide when the weeds are still very small. St. Augustinegrass is very sensitive to some herbicides, such as 2,4-D. Read the label carefully before applying any herbicide to ensure that it is the right product for the weeds you have and that you do not damage the turf. Follow all instructions on the label. It explains how and when to use the product and how much to apply.

Controlling insects

Chinch bugs and white grubs are the two most serious insect pests in St. Augustinegrass lawns. Routinely check for these pests and treat as necessary.

Controlling thatch

If the thatch layer (a layer of undecomposed plant matter) is more than 3/4 inch thick, mow the lawn with a vertical mower or scalp the lawn (cut with a rotary mower at its lowest setting) in April or May when the grass is healthy and actively growing.

Eliminating compacted soil

In areas of heavy traffic, aeration can help eliminate compacted soils. Use a core-aerating machine when the grass is actively growing. If you have an underground irrigation system, flag the sprinkler heads first to avoid damaging them.

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June through September

Mowing

Follow the same recommendations as for March through May.

Fertilizing

Continue the fertilizer program begun in the spring, applying 1 to 1 1/2 pounds of nitrogen per 1,000 square feet every 8 to 10 weeks. Without soil test information, it is recommended that you use a fertilizer that either contains nitrogen only (21-0-0, ammonium sulfate) or is low in phosphorus (Examples: 21-3-6 or 15-0-15) to reduce the chance of excessive phosphorus build-up in the soil. Such build-ups can lead to deficiencies in iron and zinc.

To prevent yellowing caused by iron chlorosis, apply liquid or granular iron fertilizer throughout the growing season. Follow the label directions for the rate of application. Fertilizers containing iron may stain concrete, brick or stone surfaces.

Watering

Follow the same recommendations as for March through May.

Controlling weeds

Continue applying postemergent herbicide as needed. Herbicides containing 2,4-D should be used with care, as St. Augustinegrass is sensitive to this herbicide. Herbicides may damage the lawn if you apply them when the temperature is higher than 90 ºF.

Controlling insects

Follow the same recommendations as for March through May. The most effective time to treat for white grubs is in August when they are immature and close to the soil surface.

Eliminating compacted soils

Follow the same recommendations as for March through May.

September through February

Mowing

Continue the recommended mowing practices until the grass goes dormant and does not require mowing.

Fertilizing

Continue fertilizing as recommended until 4 to 6 weeks before the first expected frost. At that time, apply a low nitrogen, high-potassium fertilizer such as 5-10-10. Apply no more than 1/2 pound of nitrogen per 1,000 square feet. To calculate the amount of product needed per 1,000 square feet, substitute 50 for 100 in the spring formula.

Do not fertilize St. Augustinegrass from December through February unless the lawn has been overseeded (planted with cool-season grass to maintain its green color in the winter). Fertilize overseeded lawns once in December and again in February with 1/2 pound of nitrogen per 1,000 square feet, using a nitrogen-only fertilizer such as 21-0-0.

Have the soil tested to determine the nutrients needed. In the absence of a soil test, use a complete fertilizer with a 3- 1-2 ratio of nitrogen, phosphorus and potassium.

Watering

Even though St. Augustinegrass is normally dormant in winter, you may still need to water it periodically when the weather is warm, dry and windy. If the lawn has been overseeded, water as you would from March through May.

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Controlling weeds

Apply preemergent herbicides for annual winter weeds when the average soil temperature drops to 70º F. Your county Extension agent can give you an estimate of that date in your area. Apply postemergent herbicides as needed.

Controlling insects

St. Augustinegrass lawns should experience no detrimental insect activity during the winter.

Produced by Agricultural Communications, The Texas A&M University System

Comments

  1. Jeff Novak says:

    My existing yard has areas with sand under the grass. I have been advised to spread 1/2″ of black cow over these areas. Other people advise 1/2″ of topsoil. will top soil burn the grass ?
    Thanks,

    Jeff Novak

  2. I didn’t realize that different types of grass would need to be treated differently. I like that this type of grass will go dormant in the winter so I won’t have to mow it. That would be a nice break! I also like your tip to not fertilize in the winter. Thanks for these tips!

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