Ornamental · Poaceae
St. Augustine Grass
Stenotaphrum secundatum
Give it warmth, steady water, and the right mowing height, and St. Augustine grass knits into a thick, carpet-like lawn.
Full sun
Every 3–7 days
60–365 days
USDA 8–10
Overview
St. Augustine grass is the lawn of the warm, humid South, a coarse-bladed turf that spreads by above-ground runners called stolons until it forms a dense, carpet-like mat. It greens up early in spring and holds its color through the heat, which is why it covers so many yards across the Gulf Coast and Florida. It handles some shade better than most warm-season grasses, though it still wants sun for the best stand.
It is a perennial built for warmth, not cold. The grass thrives in the heat and goes dormant and brown once winter chill sets in, and a hard freeze can thin or kill an unprotected lawn. That preference for warmth is what ties it to the Gulf states, where it never sits cold for long.
The trade-off for that lush, fast cover is upkeep. St. Augustine grass needs regular water and steady feeding, and it draws more than its share of pests and diseases, the southern chinch bug worst of all. Mow it at the right height, water deeply, and keep the nitrogen in check, and it pays you back with a thick, even lawn.
Care
The short version: plant it in sun to part shade, keep the soil evenly moist with about 1/2 to 3/4 inch per watering, mow tall at 3 to 4 inches, and feed it nitrogen through the warm season without overdoing it.
Light
St. Augustine grass does best in full sun but takes partial shade better than most warm-season turf. Give it as much sun as you can for a dense stand, since deep shade leaves it thin and weak.
Water
Keep the soil evenly moist and water when the blades fold, wilt, or turn blue-gray, putting down about 1/2 to 3/4 inch each time. The grass needs regular moisture and only handles moderate drought, so don't let it dry out for long.
Soil
It adapts to many soils but prefers well-drained ground at a medium to low pH, somewhere between 6.0 and 7.5. On alkaline soils the grass may yellow and need a dose of iron to green back up.
Temperature
This is a warm-season grass that grows through heat up to about 95°F (35°C). Cold is its weak point, since it browns out in winter dormancy and a hard freeze near 25°F (-4°C) can thin or kill the lawn.
Humidity
It is right at home in high humidity, which is part of why it thrives along the muggy Gulf Coast. Damp, warm air does feed several of its fungal diseases, so airflow and dry mowing matter more than the humidity itself.
Feeding
Feed it nitrogen through the warm season, anywhere from 2 to 6 applications a year depending on your climate. Go easy on the quick-release soluble nitrogen, which only feeds chinch bug damage instead of the lawn.
Pruning
Mow standard cultivars tall, at 3 to 4 inches, and the dwarf types lower, around 2 to 2.5 inches. Never take off more than a third of the blade in one pass, or you stress the grass and open the door to weeds.
Repotting
none
Size & spacing
The blades stand only about 3 to 4 inches (8 to 10 cm) tall once mowed, but the stolons creep outward, with a single plant spreading roughly 1 to 3 feet (30 to 100 cm) as it knits into a mat.
When to plant
St. Augustine grass runs on warmth, so you start it while the grass is growing hard. Lay sod, plugs, or sprigs in spring or in late summer to early fall, steering clear of cold snaps and hot, dry spells. The lawn greens up in spring and slips into a brown dormancy once winter cold arrives.
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 shows up as patches of dying or yellowing turf, and the cause depends on the season and the weather. Read the timing and the look of the damage and you can tell a chinch bug summer from a fungal fall. Match what you see below, then act before the patch spreads.
Spreading yellow-brown patches in hot, sunny spots
This is almost always the southern chinch bug, the pest that does more damage to St. Augustine grass than any other. The insects suck sap along sunny, dry edges in the heat of summer, and the dying turf spreads outward from there. Treat the patch and the green grass around it as soon as injury shows, ease off the quick-release nitrogen, and water well, since heavy rain or irrigation knocks the bugs back.
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 stays yellow after feeding
A lawn that turns mottled yellow and refuses to green up after a feeding likely has St. Augustine Decline, a virus with no chemical cure. Before you blame it, rule out an iron or manganese shortage on alkaline soil, which a dose of iron can fix. If it really is SAD, replant with a resistant cultivar like Floratam or Raleigh, plug it in on 2 to 3 foot centers, and let it crowd 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 with leaves that pull free
Rounded patches that show up in the cool, damp days of fall and spring point to large patch, a Rhizoctonia fungus. The giveaway is at the patch edge, where the leaves tug loose from dark, rotted sheaths. Hold the fertilizer for summer when the grass is growing hard, cut back on water, and aerate compacted ground so it drains.
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 edges on the blades
Tan-to-gray lesions ringed in purple are the mark of gray leaf spot, a fungus that flares in warm, wet weather on lawns pushed with too much nitrogen. Mow only when the blades are dry and bag the clippings while the spots are active. The lasting fix is to cut the nitrogen back and keep the leaves from staying wet for long stretches.
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
Good news for pet owners: St. Augustine grass is a plain lawn turfgrass with nothing toxic in it. Cats, dogs, horses, and the rest can walk on it and nibble it without risk of poisoning. A pet that gulps grass may sometimes throw up, but that is the blades scratching the stomach, not a toxin, and the pollen is the only thing likely to bother an allergy-prone person.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat can chew this lawn grass without harm. The most you might see is the odd hairball or a little vomiting from the blades themselves, which is mechanical rather than poisoning.
Dogs None
Dogs are safe on and around it. Some dogs graze a few blades and bring them back up, but that's the grass scratching the stomach, not a toxin at work.
Horses Safe
Horses can graze St. Augustine grass with no risk of poisoning.
Rabbits Safe
Rabbits can nibble the blades safely, as this is a plain turfgrass with nothing toxic in it.
Livestock Safe
Cattle, goats, and sheep can graze it without trouble.
Birds Safe
Backyard birds and poultry can peck through it freely. Nothing in the plant poses a hazard.
People Safe
The grass is harmless to people, though the pollen can set off 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 comes in several named cultivars, and the right one depends on your climate and which pests you fight most. These are the ones worth knowing.
Floratam
This is the most widely planted cultivar, a coarse and vigorous grass that resists the SAD virus but takes cold and shade poorly.
Palmetto
A popular pick with better cold hardiness, though it isn't insect-resistant and can struggle with disease in humid climates.
Raleigh
Bred at NC State for cooler northern areas, this cold-hardy, SAD-resistant cultivar still falls prey to chinch bugs and large patch.
Seville
A fine-leaved, dark green dwarf type that shrugs off SAD but remains open to chinch bug and webworm damage.
Captiva
A University of Florida dwarf cultivar that resists southern chinch bugs and grows low enough to need less mowing.
How to propagate
You don't grow this grass from a seed packet. It spreads on its own runners, which makes plugs, sprigs, and sod the way to start or patch a lawn.
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
Start a new lawn in spring or late summer to early fall, while the grass is growing hard. You spread it vegetatively as sod, plugs, or sprigs, cutting sod into small squares for plugs and spacing them 6 to 24 inches apart, with tighter spacing filling in faster. Sod knits down quickest, while plugs and sprigs take several weeks to a few months to cover. It is never started from seed.
Myths
St. Augustine grass can be grown from seed like other lawn grasses.
It sets almost no viable seed, so seeding rarely works. You establish it vegetatively instead, by laying sod or planting plugs and sprigs.