Good St. Augustine grass care in Charleston comes down to a few habits done well. Mow it tall. Feed it through summer but not in spring or fall. Water deeply and only when it needs it. Watch closely for chinch bugs in hot, dry weather and for large patch when the weather cools. St. Augustine is the classic Lowcountry lawn, the wide bladed grass you see under live oaks in West Ashley, on James Island and across Mount Pleasant. It handles heat, humidity and even some salt spray, and it tolerates more shade than any other warm season grass. It also has a few weak spots that every owner should know about.
Why St. Augustine suits the Lowcountry
St. Augustine loves heat and humidity, and it grows well in the sandy soils common along the coast. Clemson Cooperative Extension calls it the most shade tolerant warm season grass, although it still needs roughly 4 to 6 hours of sun a day. It spreads by thick above ground runners, which lets it fill in bare spots and crowd out many weeds.
It has downsides. It does not handle heavy foot traffic well, it is planted as sod or plugs rather than seed, and it is prone to chinch bugs, large patch and gray leaf spot.
Common varieties
Clemson lists several cultivars that show up in South Carolina.
| Type | Examples | Notes |
|---|---|---|
| Standard | Raleigh, Palmetto, Mercedes | Raleigh is known for cold tolerance |
| Standard | Floratam | Poor cold tolerance, some chinch bug resistance |
| Dwarf | Captiva, Seville, Sapphire, Delmar | Finer texture, lower mowing height; Captiva has some chinch bug resistance |
St. Augustine grass care in Charleston through the year
| Season | Key tasks |
|---|---|
| January to March | Soil test. No nitrogen. Preemergent for summer weeds on the coast in late winter. |
| April | Cleanup mow at 2 to 2.5 inches before green up. Hold off on nitrogen. |
| May to August | Mow 2.5 to 4 inches. Feed in early May, June or July, and by about August 15. Watch for chinch bugs and gray leaf spot. |
| September to October | Raise mower slightly. No nitrogen. Potassium if the soil test calls for it. Watch for large patch. |
| November to December | Keep leaves off the lawn. Water during long dry spells. |
Mowing
Mowing height is where most St. Augustine problems start. Clemson recommends 3 to 4 inches for standard varieties and about 2.5 inches for dwarf types. Keep it toward the top of the range in shade, and raise it by half an inch to an inch during heat and drought stress. A taller lawn has deeper roots, shades out weeds and holds up better against insects.
Mow often enough to remove no more than one third of the blade at a time, which usually means weekly in summer. Use a sharp blade. St. Augustine's wide leaves show torn, brown tips quickly when the blade is dull. Our guide to mowing height for warm season grass covers the details for every Lowcountry grass.
Fertilizing
Clemson recommends 2 to 4 pounds of actual nitrogen per 1,000 square feet per year for St. Augustine, with the higher end on sandy soils. That is typically split into three feedings of half a pound to 1 pound each:
- Early May, after the lawn has fully greened up
- June or July, ideally with a high potassium product like 15-0-15
- A final feeding before about August 15
No nitrogen in early spring or fall. Early nitrogen feeds weeds and risks frost damage to new growth. Late nitrogen encourages large patch and leaves the grass tender going into winter. Apply phosphorus and lime only if a soil test calls for them. Clemson lists a target pH of 6.0 to 6.5 for St. Augustine.
Overfeeding is a common mistake. Lush, heavily fed St. Augustine is exactly what chinch bugs prefer. For the full timing picture, see the best time to fertilize a lawn in Charleston SC.
Watering
Clemson recommends applying three quarters of an inch to 1 inch of water when the lawn shows stress, then letting it dry out before watering again. Signs of stress include leaf blades folding or rolling, a bluish gray color, and footprints that stay visible after you walk across the grass.
Water early in the morning. Evening watering leaves the grass wet overnight, which favors gray leaf spot and large patch. Short daily cycles on a timer keep roots shallow.
Most St. Augustine problems our crews at Right Stuff Lawn Care see trace back to three habits: mowing too short, feeding at the wrong time, and watering too often.
Pests and diseases to watch
Chinch bugs
Chinch bugs are the most damaging insect pest of St. Augustine in coastal South Carolina. They are tiny, and they feed by sucking sap from the grass and injecting a toxin. Damage starts as yellowing patches that turn brown and die, usually in the hottest, sunniest spots near driveways, sidewalks and streets. Clemson notes two to three generations a year in South Carolina, with damage most common in hot, dry summer weather.
To check, part the grass at the edge of a yellowing area and look at the soil surface for small black insects. Avoid overfeeding, keep thatch in check, and water properly. If numbers are high, an insecticide labeled for chinch bugs in lawns may be needed. We cover this pest in depth in chinch bugs in St. Augustine lawns.
Large patch
Large patch is a fungal disease that shows up as circular yellow to brown patches, sometimes several feet across, with an orange or smoky ring at the edge. In the Lowcountry it is most active in spring and fall when soil temperatures are cool to mild, and it is worse with late season nitrogen, excess water and poor drainage. Clemson notes that preventive fungicide starting in early fall can help lawns with a history of the disease, because recovery is slow once weather cools.
Gray leaf spot
Gray leaf spot shows up in hot, humid weather as small oval spots on the leaves, often gray or tan with purple or brown borders. It is worse on heavily fed lawns and lawns that stay wet overnight. Morning watering and moderate nitrogen help. Severe cases may need a labeled fungicide.
Frequently asked questions
How tall should St. Augustine grass be in Charleston?
Clemson recommends 3 to 4 inches for standard varieties and about 2.5 inches for dwarf varieties. Keep it taller in shade and during summer heat. Mowing it short is one of the most common causes of thin, weedy St. Augustine.
Why is my St. Augustine grass turning yellow and dying in summer?
In hot, dry weather, chinch bugs are the first thing to check, especially near driveways and sidewalks. Drought stress and gray leaf spot are other common causes. Parting the grass at the edge of the damage and looking for small black insects is a good first step.
Can St. Augustine grow in shade?
It handles more shade than any other warm season grass, but it still needs about 4 to 6 hours of sun. Raise the mowing height and reduce fertilizer in shaded areas. Under dense live oak canopy, beds or mulch often work better than grass.
When should I stop fertilizing St. Augustine?
Clemson's calendar puts the last nitrogen feeding before about August 15. After that, skip nitrogen until the lawn greens up the next spring. Potassium in early fall is fine if a soil test calls for it.