Ornamental · Poaceae
St. Augustine Grass
Stenotaphrum secundatum
Hand it warmth, regular water, and a nice high mow, and St. Augustine grass turns into a thick, carpet-like lawn.
Full sun
Every 3–7 days
60–365 days
USDA 8–10
Overview
So what is St. Augustine grass? It's the classic lawn of the warm, sticky South, a coarse-bladed grass that crawls along on above-ground runners, called stolons, until it fills in as a dense, carpet-like mat. It wakes up early in spring and keeps its green through the summer heat, which is exactly why you see it all over yards along the Gulf Coast and in Florida. It also puts up with some shade better than most warm-season grasses, but give it sun if you want it looking its best.
Here's the thing: this is a perennial that's all about warmth and not a fan of the cold. It loves the heat, then browns out and goes dormant when winter chill shows up, and a hard freeze can thin or wipe out a lawn that isn't protected. That's really why it sticks to the Gulf states, where it never stays cold for long.
The catch with all that fast, lush growth? A bit of upkeep. St. Augustine grass wants regular water and steady feeding, and it does pull in more pests and diseases than some lawns, with the southern chinch bug being the big one. Mow it high, water it deep, and don't get carried away with nitrogen, and it'll reward you with a thick, even lawn.
Care
The short version: pop it in sun to part shade, keep the soil evenly moist with about 1/2 to 3/4 inch of water each time, mow it tall at 3 to 4 inches, and feed it nitrogen through the warm season without laying it on thick.
Light
St. Augustine grass loves full sun, but it's more forgiving about partial shade than most warm-season lawns. Give it as much sun as you can and it'll come in nice and thick, since deep shade just leaves it thin and kind of weak.
Water
Keep the soil evenly moist and water whenever the blades fold, wilt, or go a bit blue-gray, putting down around 1/2 to 3/4 inch each time. It likes steady moisture and only handles so-so drought, so don't leave it bone dry for long.
Soil
It's not fussy and grows in all kinds of soil, though it's happiest in well-drained ground at a medium to low pH, somewhere around 6.0 to 7.5. If your soil runs alkaline and the grass looks yellow, a little iron usually greens it right back up.
Temperature
This is a warm-season grass, so it keeps chugging along in heat up to about 95°F (35°C). Cold is where it struggles, though: it browns out into winter dormancy, and a hard freeze near 25°F (-4°C) can thin or even kill the lawn.
Humidity
It's totally at home in high humidity, which is part of why it does so well along the muggy Gulf Coast. The downside? That warm, damp air feeds a few of its fungal diseases, so good airflow and mowing when it's dry matter more than the humidity itself.
Feeding
Feed it nitrogen through the warm season, anywhere from 2 to 6 applications a year depending on where you live. Go easy on the quick-release soluble stuff, though, because too much just feeds chinch bug damage instead of the lawn.
Pruning
Mow the standard cultivars tall, at 3 to 4 inches, and the dwarf types a bit lower, around 2 to 2.5 inches. Just don't take off more than a third of the blade in one go, or you'll stress the grass and give weeds an opening.
Repotting
none
Size & spacing
Once it's mowed, the blades only stand about 3 to 4 inches (8 to 10 cm) tall, but the stolons keep creeping sideways, so a single plant can spread roughly 1 to 3 feet (30 to 100 cm) as it weaves into a mat.
When to plant
Since this grass is all about warmth, you'll want to start it while it's actively growing. Lay sod, plugs, or sprigs in spring or from late summer into early fall, and just dodge the cold snaps and the hot, dry stretches. It greens back up in spring and slips into a brown, dormant phase once winter cold arrives, which is totally normal.
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 of the time, St. Augustine grass problems look the same: patches of yellow or dying turf. What's behind them, though, depends on the season and the weather. Once you get a feel for the timing and how the damage looks, it's pretty easy to tell a summer chinch bug from a fall fungus. Find the match below, then get on it before the patch spreads.
Yellow-brown patches spreading in the hot, sunny spots
If patches like this are creeping outward, it's almost always the southern chinch bug, which does more damage to St. Augustine grass than anything else. These bugs suck sap along the sunny, dry edges during the peak of summer, and the dead turf just keeps expanding. So jump on it: treat the patch plus the healthy grass around it as soon as you spot damage, back off the quick-release nitrogen, and water well, because a good soaking or heavy rain knocks 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
Blotchy yellow lawn that won't green up after you feed it
A lawn that goes blotchy yellow and just won't green up after a feeding probably has St. Augustine Decline, a virus with no chemical fix. Before you panic, rule out an iron or manganese shortage on alkaline soil, which a bit of iron will sort out. But 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 when it's cool and wet, with leaves that pull loose
Round patches popping up in the cool, damp weather of fall or spring? That's usually large patch, a fungus in the Rhizoctonia family. The dead giveaway is at the patch edge, where the blades slip right off dark, rotted sheaths. Hold off on feeding until summer when the grass is really growing, water less, and aerate any packed-down soil so it drains better.
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
Those tan-to-gray spots ringed in purple? That's gray leaf spot, a fungus that shows up in warm, wet weather on lawns that got too much nitrogen. Mow only when the blades are dry and bag the clippings while the spots are still active. The real fix, though, is to cut back the nitrogen and keep the leaves from staying wet too long.
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 if you've got pets: St. Augustine grass is just a plain lawn turfgrass with nothing toxic in it. Cats, dogs, horses, you name it, they can walk on it and nibble it without any poisoning risk. Sure, a pet that scarfs down some grass might throw up, but that's just the blades scratching the stomach, not a toxin, and honestly the only real bother is the pollen, which can set off grass allergies.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat can chew on this lawn grass and be totally fine. Worst case, you might get the odd hairball or a little vomiting from the blades, but that's mechanical, not poisoning.
Dogs None
Dogs are safe on it and around it, no problem. Some will munch a few blades and bring them back up, but that's just the grass scratching the stomach, not a toxin.
Horses Safe
Horses can graze St. Augustine grass with zero risk of poisoning.
Rabbits Safe
Rabbits can nibble the blades without any worry, since it's a plain turfgrass with nothing toxic in it.
Livestock Safe
Cattle, goats, and sheep can all graze it without any trouble.
Birds Safe
Backyard birds and poultry can peck around in it all they want, since nothing in the plant will hurt them.
People Safe
It's harmless to people too, though the pollen can kick off hay-fever symptoms if you're 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 a few named cultivars, and which one's right for you really comes down to your climate and the pests you deal with most. Here are the ones worth knowing about.
Floratam
Floratam's the most widely planted one, a coarse, vigorous grass that shrugs off the SAD virus but doesn't handle cold or shade well.
Palmetto
Palmetto is a popular pick with better cold hardiness, though it's not insect-resistant and can run into disease trouble in humid spots.
Raleigh
Raleigh was bred at NC State for cooler northern areas, and while it's cold-hardy and SAD-resistant, it still gets hit by chinch bugs and large patch.
Seville
Seville is a fine-leaved, dark green dwarf that brushes off SAD but stays open to chinch bug and webworm damage.
Captiva
Captiva is a University of Florida dwarf that resists southern chinch bugs and grows low enough that you won't mow it as often.
How to propagate
Forget the seed packet with this one. It spreads on its own runners, so plugs, sprigs, and sod are how you get a lawn going or patch up a bare 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
Get a new lawn going in spring or late summer into early fall, while the grass is really growing. Since it spreads on its own, you plant it vegetatively as sod, plugs, or sprigs, cutting sod into little squares for plugs and spacing them 6 to 24 inches apart, with tighter spacing filling in quicker. Sod knits together the fastest, while plugs and sprigs take several weeks to a few months to cover, and you never start it from seed.
Myths
You can grow St. Augustine grass from seed just like other lawn grasses.
Not really, because it makes almost no viable seed, so seeding hardly ever works out. The way to go is vegetative, meaning you lay sod or plant plugs and sprigs instead.