Ornamental · Poaceae
St. Augustine Grass
Stenotaphrum secundatum
Feed it heat, faithful water, and a high mow, and St. Augustine grass takes off into a thick, carpet-like lawn.
Full sun
Every 3–7 days
60–365 days
USDA 8–10
Overview
St. Augustine grass rules the warm, humid South, and it earns that spot fast. This coarse-bladed turf throws out above-ground runners, called stolons, and races them across bare ground into a dense, carpet-like mat. It greens up early in spring and powers through the summer heat without losing color, which is why it blankets yards across the Gulf Coast and Florida. It even shrugs off more shade than most warm-season grasses, though it truly hits its stride in full sun.
This perennial was built for heat, plain and simple. It surges through hot weather, then drops into a brown dormancy the moment winter chill lands, and a hard freeze can thin or kill a lawn caught unprotected. That hunger for warmth is exactly what pins it to the Gulf states, where the cold never gets a real grip.
All that fast, lush cover comes with a to-do list, and it pays off. St. Augustine grass drinks up regular water and steady feeding, and it does draw a crowd of pests and diseases, the southern chinch bug leading the pack. Mow it high, soak it deep, and keep a firm hand on the nitrogen, and it rockets back into a thick, even lawn.
Care
The short version: drop it into sun to part shade, keep the soil evenly moist with about 1/2 to 3/4 inch each watering, mow it tall at 3 to 4 inches, and push nitrogen through the warm season without going overboard.
Light
St. Augustine grass powers ahead in full sun, and it still handles partial shade better than most warm-season lawns. Load it up with all the sun you can for a thick, full stand, because deep shade drains the vigor and leaves it thin.
Water
Keep the soil evenly moist and reach for the hose the second the blades fold, wilt, or flash blue-gray, laying down about 1/2 to 3/4 inch each time. It runs on steady moisture and takes only moderate drought, so never let it bake dry for long.
Soil
It roots into almost any soil, but it really takes off in well-drained ground at a medium to low pH, right around 6.0 to 7.5. Let the soil creep alkaline and the blades pale out, but a shot of iron snaps the green right back.
Temperature
This warm-season grass keeps sprinting through heat up to about 95°F (35°C). Cold slams the brakes, though: it browns into winter dormancy, and a hard freeze near 25°F (-4°C) can thin or kill an unprotected lawn.
Humidity
It thrives in high humidity, which is half the reason it booms along the muggy Gulf Coast. That warm, sticky air also fuels a few fungal diseases, so keep the airflow moving and mow dry blades to stay ahead of them.
Feeding
Drive it with nitrogen through the warm season, spread across 2 to 6 applications a year to fit your climate. Just rein in the quick-release soluble stuff, since a heavy hit only stokes chinch bug damage instead of the lawn.
Pruning
Run standard cultivars tall at 3 to 4 inches, and drop the dwarf types down near 2 to 2.5 inches. Never scalp off more than a third of the blade at once, or you stall the grass and hand the weeds an opening.
Repotting
none
Size & spacing
Mowed blades top out at just 3 to 4 inches (8 to 10 cm), but the stolons keep sprinting sideways, so one plant sprawls roughly 1 to 3 feet (30 to 100 cm) as it laces into a mat.
When to plant
Warmth is the green light, so start this grass while it is charging ahead. Lay sod, plugs, or sprigs in spring or from late summer into early fall, and skip the cold snaps and the hot, bone-dry stretches. Watch it green up in spring and drop into a brown dormancy the moment winter cold moves in.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Lay sod, plugs, or sprigs during active warm-season growth in spring or late summer/early fall (late fall to spring in south Florida); avoid cold and hot, dry extremes.
- Harvest: Grown as turf; not flowered or harvested. Greens up in spring and goes dormant/brown in winter cold.
Hardiness
USDA hardiness zones: 8–10
Temperature: down to -12°C
Troubleshooting
Most St. Augustine grass trouble lands the same way: patches of yellowing or dying turf. The season and the weather crack the case, though. Line up the timing against the look of the damage and a summer chinch bug practically outs itself against a fall fungus. Match your symptom below, then move before the patch takes ground.
Yellow-brown patches racing across the hot, sunny ground
When a patch keeps charging outward in the sun, point straight at the southern chinch bug, the pest that wrecks St. Augustine grass harder than any other. It pumps sap out along the warm, dry edges through peak summer, and the dead turf keeps gaining ground. Hit it fast: treat the patch and the green grass hugging it the moment damage shows, throttle back the quick-release nitrogen, and water hard, since a heavy soaking or rain drives the bugs down.
Fix:
- Treat affected and surrounding turf with a labeled insecticide as soon as injury appears, targeting both nymphs and adults
- Avoid excess soluble nitrogen, which accelerates chinch bug buildup
- Irrigate adequately, since heavy irrigation or rainfall suppresses populations
- Consider a resistant cultivar such as Floratam when renovating
Mottled yellow lawn that won't green up after feeding
When the lawn mottles yellow and flat-out refuses to green up after a feeding, suspect St. Augustine Decline, a virus with no chemical cure. First knock out an iron or manganese shortage on alkaline soil, which a dose of iron will fix. If SAD is the verdict, replant with a resistant cultivar like Floratam or Raleigh, plug it on 2 to 3 foot centers, and let it muscle out the sick grass.
Fix:
- Replant with a SAD-resistant cultivar (for example Floratam, Floralawn, Raleigh, or Seville), plugging it in on 2 to 3 foot centers to crowd out diseased grass
- Rule out iron/manganese deficiency on alkaline soil with supplemental iron
- Use clean, virus-free sod or plugs
Round brown patches in cool, wet weather, leaves lifting free
Round patches that pop up in the cool, damp weather of fall or spring usually spell large patch, a Rhizoctonia fungus. Zero in on the patch edge, where the blades peel off dark, rotted sheaths with barely a tug. Park the fertilizer until summer growth, dial the watering back, and aerate any packed soil so the water runs through.
Fix:
- Limit fertilizer to summer when turf is actively growing
- Avoid mowing too low and avoid over-irrigation
- Aerate to reduce compaction and improve drainage
- Apply a preventive fungicide in fall when soil temperatures favor the pathogen
Gray oval spots with dark purple rims on the blades
Tan-to-gray lesions rimmed in purple call out gray leaf spot, a fungus that ignites in warm, wet weather on lawns overloaded with nitrogen. Mow only on dry blades and bag the clippings while the spots stay hot. The knockout move is to slash the nitrogen and keep the leaves from sitting wet.
Fix:
- Mow at the proper height and only when grass is dry
- Bag and dispose of clippings while disease is active
- Reduce nitrogen and avoid prolonged leaf wetness
- Apply a labeled fungicide if needed
Toxicity
Great news for pet lovers: St. Augustine grass is a plain lawn turfgrass with nothing toxic in it. Cats, dogs, horses, the whole crew can roll on it and nibble it with zero poisoning risk. A pet that gulps a mouthful might bring it back up, but chalk that up to the blades scratching the stomach, not a toxin, and only the pollen is likely to nag an allergy-prone nose.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat can chomp this lawn grass with no harm at all. Worst case, it coughs up a hairball or brings up a little from the blades, and that is mechanical, not poisoning.
Dogs None
Dogs romp on it and around it safely. Some crop a few blades and bring them back up, but that is the grass scratching the stomach, not a toxin.
Horses Safe
Horses can graze St. Augustine grass with no risk of poisoning.
Rabbits Safe
Rabbits can nibble the blades safely, since this is a plain turfgrass with nothing toxic in it.
Livestock Safe
Cattle, goats, and sheep can graze it without any trouble.
Birds Safe
Backyard birds and poultry can peck through it freely, since nothing in the plant can hurt them.
People Safe
It is harmless to people, though the pollen can fire up hay-fever symptoms in anyone prone to grass allergies.
The grass is not poisonous. Pets that nibble lawn grass may occasionally vomit, but this is mechanical, not poisoning. Grass pollen can trigger hay-fever-type allergies in sensitive people and pets.
Varieties
St. Augustine grass shows up as a handful of named cultivars, and the winner depends on your climate and the pests you square off against. Here are the ones worth chasing down.
Floratam
Floratam leads as the most widely planted cultivar, a coarse, vigorous grass that beats the SAD virus but caves to cold and shade.
Palmetto
Palmetto draws a crowd for its stronger cold hardiness, though it packs no insect resistance and can wrestle disease in humid climates.
Raleigh
Raleigh, bred at NC State for cooler northern turf, brings cold hardiness and SAD resistance but still gets hammered by chinch bugs and large patch.
Seville
Seville, a fine-bladed, dark green dwarf, throws off SAD yet stays wide open to chinch bug and webworm damage.
Captiva
Captiva, a University of Florida dwarf, fends off southern chinch bugs and stays low enough to slash your mowing.
How to propagate
Skip the seed aisle entirely. This grass charges out on its own runners, so plugs, sprigs, and sod are how you launch a lawn or patch a thin spot.
DivisionEasy
During active warm-season growth in spring or late summer/early fall · Several weeks to a few months for plugs/sprigs to fill in; sod establishes fastest
Kick off a new lawn in spring or from late summer into early fall, right when the grass is charging. Since it spreads itself, plant it vegetatively as sod, plugs, or sprigs, slicing sod into small squares for plugs and spacing them 6 to 24 inches apart, with tighter spacing closing in faster. Sod knits down quickest, plugs and sprigs need several weeks to a few months to cover, and seed never enters the picture.
Myths
You can seed St. Augustine grass like any other lawn grass.
Not a chance, since it sets almost no viable seed and sowing rarely takes. You launch it vegetatively, laying sod or planting plugs and sprigs.