St. Augustine Grass in South Florida
St. Augustine grass is one of the most popular grasses used for lawns in South Florida. St. Augustine grass (Stenotaphrum secundatum) is a warm weather, subtropical grass which can be found throughout the United States, Canada, Mexico, South America, western and southern Africa, the Caribbean, the Hawaiian Islands, and Oceania. Common varieties include Texas Common, Raleigh, Seville, Palmetto and Floratam, where each variety has its own unique characteristics.
St. Augustine grass is a darker green grass with a coarse texture. It has a low, dense growth proclivity. It tends to grow well across all soil types and tolerates shade, heat, salinity with moderate drought resistance. It is however susceptible to waterlogged soil or extended periods of cold weather. St. Augustine grass can be an aggressive species which spreads rapidly via stolons – above ground growth structures used to spread a plant’s reach.
If managed properly, St. Augustine Grass forms a dense cover that handles light foot traffic and outcompetes most weeds providing a uniform looking lawn. St. Augustine Grass is the most shade tolerant warm-season turfgrass.
You can keep your St. Augustine grass lawn looking healthy and beautiful with the proper maintenance. The Texas A&M University system is an excellent resource and pretty much the authority on maintaining St. Augustine grass. The following provides a set of guidelines, by season, to follow to keep your St. Augustine grass lawn in peak conditions when considering mowing, watering and fertilizing, while taking into account your property’s need for controlling weeds, insects, thatch, and eliminating compacted soil.
Note that these are general recommendations which may not apply to every situation. Be sure to contact a professional to understand what landscape solutions might be right for you given your unique property.
Spring: March through May
Mowing
Mowing is all about a routine, like much else in life. Begin a routine mowing program as soon as the grass begins to turn green in the spring. You don’t want to remove any more than a third (1/3) of the leaf area with any one mowing. This usually implies a Set the mowing height of two and a half to three inches, adding a half inch for shady areas; if you have a professional lawn mowing service then they’ll know what to do.
Frequent mowing at a lower height produces higher quality turfgrass. You don’t need to worry about bagging the grass clippings, as they quickly decompose which can return important nutrients back to the soil. Otherwise, you can use clippings for compose elsewhere.
Fertilizing
Fertilizing is a critical step to keep your lawn looking its best. You’ll want to start fertilizing about three weeks after the grass turns green, basically when there’s no further chance of a late frost. Apply one (1) pound of soluble nitrogen per 1,000 square feet of lawn every eight (8) weeks, or eleven and a half (11.5) pounds of slow-release nitrogen every ten (10) weeks.
You’ll definitely want to have your soil tested to determine what added nutrients your lawn may need. For information on soil testing procedures, contact your lawn professional. You’ll likely need a complete fertilizer with a “3-1-2 ratio” of nitrogen, phosphorus and potassium.
For example, 15-5-1 or 21-7-14. Fertilizer bags come with this nutritional analysis printed on the bag. To figure out how much fertilizer you need, the first number on the package is the number of pounds nitrogen in the bag, the second and third being the weight of the phosphorus and potassium respectively.
Watering
You only want to water your lawn when the grass needs it to keep it healthy. When you water you want to wet the soil to a depth of 6 inches. You don’t need to water again until the grass starts to show symptoms of drought stress, which may present itself as a dull, bluish color, rolled or folded leaves, and footprints that aren’t righting themselves. This usually happens after five to ten (5 to 10) days, though it can also depend on the weather.
Follow these steps to determine how long to water to apply the right amount.
1. Put out five or six (5 or 6) cans with their tops open as randomly as you can around the lawn. Tuna or cat food cans work great for this.
2. Turn on the sprinklers or irrigation system for 30 minutes.
3. Measure the depth of water caught in each individual can with a ruler and write down the depths.
4. Calculate the average depth of water of all the cans.
5. Use a garden spade or a soil probe to figure out how deep the soil was wet during the 30-minute period.
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.
As an example, if you calculated an average of half an inch of water from your cans over 30 minutes and wet the soil to a depth of three inches, you would need to apply 1 inch of water to wet the soil to a depth of 6 inches, which means watering for an hour.
Run-off from watering a lawn can waste a significant amount of water, which is costly and a poor use of an important natural resource. Run-off severity can be affected by soil type and the application rate of the sprinkler system. Make sure you don’t apply water faster than the soil can absorb it.
Steps to take to prevent run-off:
- Watch the lawn while watering. If water is running into the streets or gutters, take note of how long it took before the run-off occurred. Don’t water your lawn any longer than this.
- Stop watering and allow the soil surface to dry which might take 30 minutes to an hour.
- If you have an automatic irrigation system, change your timer to the new, shorter time found in Step 2.
- Repeat until water has been applied to wet the soil to a depth of six (6) inches.
Other Spring Landscape Considerations
Controlling for weeds
The best weed control is a healthy, dense lawn. If you do need to weeds like crabgrass or other grassy weeds, you can apply preemergent herbicides. Preemergent herbicides control weeds before they sprout from the ground, which is best done in the spring when soil temperature reaches 65ºF (note: a good sign to watch for is when redbud and dogwood trees begin to bloom). Apply postemergent herbicides – herbicides which control weeds that have already sprouted – as needed. when weeds are present, but only when the grass is healthy and actively growing or you may further distress the St. Augstinegrass.
Weed control is most effective if applied early when weeds are still small. St. Augustine grass is very sensitive to some herbicides like 2,4-D. Ensure all products used for weeds are safe for use with St. Augustine grass or risk damaging the turf.
Controlling for insects
St. Augustine grass lawns are susceptible to Chinch bugs and white grubs. Routinely check for these pests and treat as necessary. Spring is a good time for a checkup.
Controlling thatch
Thatch is a a layer of undecomposed plant matter. If this layer gets to be more than three quarters of an inch (3/4”) thick, the lawn will need attention. It will need to be mowed with a vertical mower or, or be scalped with a rotary mower at its lowest setting. You’ll want to do this in April or May when the grass is healthy and actively growing.
Eliminating compacted soil
Aeration can help eliminate compacted soils formed by heavy foot traffic or use. A lawn professional can use a core-aerating machine at a time when the grass is actively growing. It’s a good idea to flag any underground sprinkler heads if you have an irrigation system.
Summer: June through September
Mowing
Follow the same routine as for March through May. Frequent mowing promotes a healthy lawn.
Fertilizing
You should be continuing the fertilizer process that was begun in the spring, applying one (1) to one and a half (1.5) 1pounds of nitrogen per 1,000 square feet every eight (8) to ten (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, making sure not to overwater in the summer months.
Controlling weeds
Continue applying postemergent herbicide as needed. As always, herbicides containing 2,4-D should be used with extreme care. It’s possible for herbicides to damage the lawn if applied when the temperature exceeds 90 ºF.
Controlling insects
Follow the same recommendations as for March through May. If you’ve noticed white grubs, the most effective time to treat for white grubs is in August when they are immature and reside close to the soil surface.
Eliminating compacted soils
Follow the same recommendations as for March through May
Fall and Winter: September through February
Mowing
Continue the mowing routine until the grass goes dormant and doesn’t need to be mowed as frequently.
Fertilizing
Continue the fertilizing schedule until four to six (4-6) weeks before the first expected frost. When that time comes, apply a low nitrogen, high-potassium fertilizer such as 5-10-10. Don’t apply more than half a pound (1/2) of nitrogen per 1,000 square feet.
You shouldn’t need to fertilize St. Augustine grass from December through February unless the lawn has been overseeded, which is when it’s planted with cool-season grass to maintain its green color through the winter. Fertilize overseeded lawns once in December and again in February with half a pound (1/2) of nitrogen per 1,000 square feet using nitrogen-only fertilizer like 21-0-0. You should have the soil tested to determine the nutrients needed.
Watering
You may still need to water St. Augustine grass periodically in the winter even though its dormant if the weather has been warm, dry, and windy. If the lawn has been overseeded, water as you would in the Spring from March through May.
Controlling weeds
Now is the time to apply preemergent herbicides for annual winter weeds when the average soil temperature gets to 70 ºF. Apply postemergent herbicides as needed.
Controlling insects
St. Augustine grass lawns don’t typically experience no detrimental insect activity during the winter.
