Ornamental · Poaceae
St. Augustine Grass
Stenotaphrum secundatum
Coarse green blades and creeping stolons weave St. Augustine grass into a thick, carpet-like mat underfoot.
Full sun
Every 3–7 days
60–365 days
USDA 8–10
Overview
Up close, St. Augustine grass shows a coarse blade, its leaves broad and heavier than the fine foliage of the dwarf cultivars. The plant travels by stolons, above-ground runners that creep along the soil surface and root as they spread, knitting into a dense, carpet-like mat. Its blades flush green early in spring and hold that color through the summer heat. This is the lawn grass of the warm, humid South, laid thick across the Gulf Coast and Florida.
Season by season, the color tells the story. Through the heat the blades stay green and firm, and when a drought sets in they fold, wilt, and take on a blue-gray cast as they lose water. Winter chill drains the color entirely: the whole stand browns and goes dormant, and a hard freeze can leave an unprotected lawn thinned or dead. A perennial at heart, it revives from the same stolons when warmth returns to the Gulf states.
The surface underfoot is thick and even, the product of stolons crowding together into one continuous carpet. That density comes at a cost, since the plant draws regular water and steady feeding and hosts more pests and diseases than many grasses, the southern chinch bug worst among them. Kept at the right mowing height and watered deep, the blades stand close-packed and uniformly green.
Care
The short version: it grows in sun to part shade, its coarse blades staying evenly moist at about 1/2 to 3/4 inch per watering, mowed tall at 3 to 4 inches, and fed nitrogen through the warm season in moderation.
Light
The coarse blades color and thicken best in full sun, though this grass holds up in partial shade better than most warm-season turf. The more light it gets, the denser and greener the stand, while deep shade thins the blades and leaves them weak.
Water
Watch the blades for thirst: they fold, wilt, and shift to a blue-gray cast as the soil dries. Watering to keep the ground evenly moist, about 1/2 to 3/4 inch each time, brings the green back, since the grass carries only moderate drought tolerance.
Soil
The roots and stolons run best through well-drained ground at a medium to low pH of 6.0 to 7.5, though the plant takes to many soils. On alkaline soil the blades fade to yellow, and iron returns them to green.
Temperature
The blades grow and stay green through heat up to about 95°F (35°C). Cold strips the color: the stand browns into winter dormancy, and a hard freeze near 25°F (-4°C) can thin or kill an unprotected lawn.
Humidity
The grass keeps its color in high humidity, thriving in the damp air of the Gulf Coast. That same moisture on the blades feeds several fungal diseases, so airflow and mowing dry foliage protect the leaves more than the humidity level itself.
Feeding
Nitrogen through the warm season keeps the blades deep green, spread over 2 to 6 applications a year to fit the climate. Too much quick-release soluble nitrogen only feeds chinch bug damage rather than greening the lawn.
Pruning
Standard cultivars are mowed tall at 3 to 4 inches, keeping the coarse blades upright, while dwarf types are cut lower, near 2 to 2.5 inches. Cutting away more than a third of the blade at once scalps the leaf, stresses the plant, and opens gaps for weeds.
Repotting
none
Size & spacing
Mowed, the blades stand only about 3 to 4 inches (8 to 10 cm) high, a low, even pile. Below them the stolons snake outward, a single plant reaching roughly 1 to 3 feet (30 to 100 cm) as its runners root and knit the mat together.
When to plant
The blades color up and grow only in warmth, so a new stand goes down while the plant is green and active. Sod, plugs, or sprigs are laid in spring or from late summer into early fall, clear of cold snaps and hot, dry spells. Each spring the color floods back, and each winter the blades brown into dormancy as the 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 reads on the blades themselves, as patches of yellow or browning turf set against the healthy green. The color, shape, and timing of the damage point to the cause, separating a summer chinch bug from a fall fungus. Match the look of your patch to the entries below and act before it widens.
Yellow-brown patches spreading through hot, sunny turf
Turf that yellows, then browns, and dies outward in the sun almost always carries the southern chinch bug, which harms St. Augustine grass more than any other pest. Small black-and-white winged adults and reddish nymphs feed on sap along the warm, dry edges through summer, and the dead patch widens from there. Treat the patch and the green blades around it as damage shows, cut back the quick-release nitrogen, and water heavily, since a soaking knocks the insects 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
Blades mottled yellow that stay pale after feeding
Blades that mottle yellow and never fully green up after a feeding often signal St. Augustine Decline, a virus with no chemical cure. An iron or manganese shortage on alkaline soil paints a similar yellow and clears with iron, so it is ruled out first. True SAD means replanting with a resistant cultivar such as Floratam or Raleigh, plugged on 2 to 3 foot centers to overtake the sick turf.
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 with sheaths rotted dark at the edge
Rounded patches breaking out in the cool, wet weather of fall and spring mark large patch, a Rhizoctonia fungus. At the rim of each patch the blades slip loose from dark, rotted sheaths with barely a pull. Hold the fertilizer until summer growth, ease off the water, and aerate compacted soil 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
Tan-gray oval lesions edged in dark purple on the blades
Elongate lesions running tan to gray with dark purple borders along the leaf blades are gray leaf spot, a fungus of warm, wet weather on over-fed turf. Mow only when the blades are dry and bag the clippings while the lesions are active. Cutting the nitrogen and keeping the leaves from staying wet clears it for good.
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
For all its coarse texture, St. Augustine grass is a plain lawn turfgrass with nothing toxic in it. Cats, dogs, horses, and the rest can chew the green blades with no risk of poisoning. A pet that swallows a mouthful may bring it up, but that is the coarse blades scraping the stomach, not a toxin, and only the pollen the grass sheds is likely to bother an allergy-prone nose.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat can chew the green blades with no harm at all. At most it coughs up a hairball or brings up a little grass, and that is the coarse blades scraping the stomach, not poisoning.
Dogs None
Dogs are safe nosing through the blades and grazing them. A few bring the grass back up, but that comes from the leaves scraping the stomach, not a toxin.
Horses Safe
Horses can graze the blades of St. Augustine grass with no risk of poisoning.
Rabbits Safe
Rabbits can crop the green blades safely, since this plain turfgrass holds nothing toxic.
Livestock Safe
Cattle, goats, and sheep can graze the blades without any trouble.
Birds Safe
Backyard birds and poultry can pick through the blades freely, with no hazard in the plant.
People Safe
The blades are harmless to handle and walk on, though the pollen the grass sheds can raise hay-fever symptoms in those 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
The named cultivars differ in the look and feel of the blade, from coarse and vigorous to fine and dark green. Climate and pest pressure decide which suits a lawn. These are the ones worth knowing.
Floratam
Floratam, the most widely planted cultivar, carries a coarse, vigorous blade that resists the SAD virus but weathers cold and shade poorly.
Palmetto
Palmetto holds better cold hardiness in its blades, though it offers no insect resistance and can take on disease in humid climates.
Raleigh
Raleigh, bred at NC State for cooler northern ground, keeps a cold-hardy, SAD-resistant blade that chinch bugs and large patch still attack.
Seville
Seville shows a fine, dark green blade on a low, dwarf plant that resists SAD yet stays open to chinch bug and webworm damage.
Captiva
Captiva, a University of Florida dwarf, grows a low blade that resists southern chinch bugs and needs less frequent mowing.
How to propagate
There is no seed to sow here. The plant advances on its own stolons, creeping runners that make plugs, sprigs, and sod the way to start a lawn or fill a bare patch.
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
A stand begins in spring or from late summer into early fall, while the blades are green and growing hard. The plant roots vegetatively as sod, plugs, or sprigs, with sod sliced into small squares for plugs and set 6 to 24 inches apart, closer plugs closing the gap sooner. Sod knits into a mat fastest, plugs and sprigs take several weeks to a few months for their stolons to cover the ground, and no part of it starts from seed.
Myths
St. Augustine grass can be grown from seed like other lawn grasses.
The plant sets almost no viable seed, so sowing rarely produces a stand. It is grown vegetatively, from sod, plugs, and sprigs that root through their stolons.