St. Augustine Grass: Plugs, Shade Limits and the 5-Minute Chinch Bug Test

St. Augustine grass is a coarse, green to blue-green warm-season lawn grass that spreads by above-ground runners, takes more shade than any other warm-season lawn grass, and is planted only as sod, plugs or sprigs, because no seed exists. UF/IFAS Extension calls it the most commonly used lawn grass in Florida, and its biggest weakness is a tiny insect that prefers it: the southern chinch bug.

This guide sets the numbers from NC State’s Carolina Lawns, Clemson Extension, University of Georgia Extension, Texas A&M AgriLife and UF/IFAS side by side and names who said what where they disagree. It is a spoke of Blooming Expert’s lawn grass types guide, which compares ten grasses by region.

How do you tell St. Augustine grass from centipede grass?

Check the runner first: on St. Augustine the leaves sit opposite each other at each node, and on centipede grass they alternate, according to NC State TurfFiles and Clemson’s identification page. Then check the blade, which is wide, flat and blunt on St. Augustine. Don’t lean on the tip alone: UF/IFAS’s identification key lists the centipede tip as blunt and rounded too.

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UF/IFAS’s key also separates St. Augustine from bahia, bermuda and zoysia by its blunt tip (theirs are pointed). NC State adds carpetgrass, which has broader leaves than centipede and resembles both. Photographs of each trait are on the Clemson and NC State pages above.

Where does St. Augustine grass grow, and where does it die?

It grows in the warm, humid coastal South, and cold sets its northern edge: NC State calls it the least cold-tolerant lawn grass. The extension services draw the line like this:

• Florida: adapted to most soils and climates in the state, but dormant and brown or tan in winter in parts of it (UF/IFAS).
• Georgia: best in the middle and lower part of the state, with many lawns around Atlanta, and slow to recover after an abnormally cold winter (University of Georgia).
• South Carolina: very susceptible to winter injury, especially west of Columbia and along the northern coast; well suited to the coastal plain (Clemson).
• North Carolina: best adapted to the coastal plain; the Raleigh cultivar suits the eastern piedmont and western coastal plain. The mountain table does not list it (NC State).
• Texas: best adapted in Southeast Texas; severe winters kill it in the northern third of the state (Texas A&M).

Traffic and water matter as much as climate. Texas A&M rates traffic tolerance low and drought tolerance below bermuda and zoysia, and Georgia calls it intolerant of wear and compaction.

How much shade can St. Augustine grass take?

It needs at least 4 to 6 hours of sun a day. It is the most shade-tolerant warm-season lawn grass, but none of the sources checked promises a lawn on less than 4 hours.

In shade, mow at the higher end of the range (Clemson, UF/IFAS) and feed less, because UF/IFAS says shaded grass needs less fertilizer than grass in full sun.

Which St. Augustine cultivar: Floratam, Palmetto, Raleigh or Seville?

Choose by winter and shade: Raleigh where winters are cold, Floratam for hot, sunny, mild-winter lawns, Seville for shade. UF/IFAS and Clemson rate the same cultivars, and the table shows where they disagree.

The big disagreement is Palmetto, and UF/IFAS even contradicts itself: its table says very good chinch bug resistance, while its cultivar text says Palmetto “is not resistant to insects.” Treat that rating as unsettled. Apart from it, none of these four cultivars rates better than slight on either list: UF/IFAS’s chinch bug profile says Floratam was released in 1973 as chinch bug resistant and isolated populations adapted to it within twelve years, and NC State says to avoid Raleigh where chinch bug pressure is high. Texas A&M adds that Floratam has the best drought tolerance and poorest cold tolerance of the Texas varieties, which suits the Gulf Coast.

Which cultivar should you choose?

• Cold edge of the range: Raleigh, which NC State and Clemson both single out for cold tolerance. Plan for chinch bugs.
• Hot, sunny, mild winters: Floratam, a preferred cultivar for open sunny areas per Clemson. Give it the 6 hours UF/IFAS asks for.
• Shady yard: a dwarf such as Seville, which UF/IFAS says performs in shade and sun but is cold sensitive and prone to thatch.

St. Augustine plugs, sod or sprigs: how and when to plant

Plant plugs 6 to 12 inches apart once the soil has warmed and the grass is growing. NC State puts plugs on 6- to 24-inch centers, recommends 6 to 12 for faster fill, and does not suggest more than 12 inches on bare ground. UF/IFAS gives the same 6 to 24 inches and says closer spacing covers the ground sooner and keeps weeds out.

The reason is how the grass spreads: UF/IFAS explains that nodes on the runners make new shoots and roots, so a plug fills its gap only as fast as its runners travel. NC State warns that wide spacing can delay fill by more than a year. None of the extension sources checked gives a fill time in weeks for a given spacing, so treat a seller’s promise as unsourced.

The plug counts are grid arithmetic (1,000 square feet divided by the spacing in feet, squared), not an extension figure. NC State sets 2 inches as the minimum plug size. UF/IFAS sets plugs in same-size holes or open furrows, tamps them and waters thoroughly.

When each method goes down

Florida’s mild winters change the timing. UF/IFAS says the best time in south Florida is late fall, winter or spring, and that in central and north Florida you should avoid cold winter and hot, dry summer months.

After planting, UF/IFAS gives a watering ramp: several 5- to 10-minute irrigations a day for 7 to 10 days, then once a day for ¼ to ½ inch for 7 to 10 days, then 2 to 3 times a week. Don’t mow until the grass has pegged down, generally 14 to 21 days. The services disagree on the first feeding. UF/IFAS says to wait 30 to 60 days because the roots are not developed enough to hold the nutrients, while NC State says to feed 0.5 to 1 pound of nitrogen per 1,000 square feet every three to four weeks through the first season, staying inside its 4-pound annual limit. Follow your state’s guidance.

How high should you mow St. Augustine grass?

Clemson says to mow standard cultivars at 3 to 4 inches and dwarfs at 2 to 3. UF/IFAS says 3.5 to 4 for Floratam, and Georgia and Texas A&M go lower.

Mow high because UF/IFAS says repeated low mowing stresses the lawn, discourages deep rooting and raises the risk of scalping, and the chinch bug profile ties 3 to 4 inches to a stronger root system. Never remove more than a third of the blade, and sharpen the blade monthly in the growing season. For the July routine, see the summer lawn care guide.

How much nitrogen does St. Augustine grass need per year?

It needs 2 to 6 pounds of nitrogen per 1,000 square feet a year, depending on where you live, and NC State sets 4 pounds as the ceiling.

NC State’s basic program is 1 pound in May and 1 pound in August. Its NC State’s St. Augustinegrass calendar splits the year finer: ½ pound in May or two weeks after green-up (whichever is later), ½ pound in June, 1 pound in July, ½ pound in August and no more than ½ pound in September, with nothing after mid-September. That adds up to at most 3 pounds. UF/IFAS puts the first Florida feeding in early April (central) or mid-April (north), and caps quick-release nitrogen at 0.7 pound at a time. Some cities and counties add their own rules. To turn pounds of nitrogen into pounds of product, use the fertilizer calculator, or divide 100 by the first number on the bag, NC State’s shortcut for 1 pound of nitrogen per 1,000 square feet.

Excess nitrogen feeds three problems at once: thatch under heavy fertilizer and irrigation, large patch (UF/IFAS), and faster growth that raises chinch bug susceptibility (UF/IFAS’s chinch bug profile). And a yellow lawn is not always an iron problem: UF/IFAS says iron is not a substitute for nitrogen, but soil above pH 7.0 can cause iron or manganese deficiency, so test the soil before planting.

St. Augustine lawn calendar by month

The Carolina column follows NC State’s calendar and Carolina Lawns. UF/IFAS dates only part of the Florida year.

How do you find and stop chinch bugs in St. Augustine grass?

Look for yellow to brown, usually circular patches that start in sunny, water-stressed spots such as lawn edges along sidewalks and buildings, then confirm with the coffee-can test before you spray. UF/IFAS warns that dehydration, root rot, other diseases, nematodes and other insects can have similar symptoms, and NC State says winter frost and drought damage are sometimes mistaken for chinch bugs in spring.

The bugs suck sap from the base of the grass, and a salivary secretion they inject interferes with water and nutrient movement, so blades wilt and brown like drought (NC State). They feed in groups that kill one section of runners and then move on together, which is why the patch grows outward (UF/IFAS). They live in the thatch and top inch and a half of soil, infestations peak in early July, and spring damage often starts where last year’s stopped.

1. Cut the bottom, or both ends, off a metal coffee can.
2. Push it into the soil at the edge of the discolored grass and dig the rim in about 3 inches.
3. Fill it with water and keep it full for five minutes.
4. Count the small black bugs with white wings that float up (adults are about a quarter inch long at most).
5. Repeat at least four times around the perimeter of the damaged area.

How many bugs justify treatment depends on which NC State page you read. NC State’s St. Augustinegrass calendar says to treat at 20 or more chinch bugs per 1,000 square feet, but NC State’s chinch bug page gives an approximate threshold of 20–25 per square foot, about a thousand times more. Neither explains the gap, so ask your county extension office which count it uses. The chinch bug page prefers spot treatment of the off-color turf and a margin around it, and warns that repeated insecticide use may reduce beneficial insects. UF/IFAS’s profile cites a study naming the big-eyed bug, which NC State says looks like a chinch bug, as the most numerous predator.

UF/IFAS says one thorough insecticide treatment may give only temporary control where chinch bugs are serious, repeat applications may be needed, and some populations resist synthetic pyrethroids. Read the label and your state’s pesticide rules. Prevention is cheaper:

• Mow at 3 to 4 inches with a sharp blade, never removing more than a third of the leaf.
• Use slow-release nitrogen and stay inside the annual limit.
• Irrigate when the blades curl, not on a timer: less than an inch usually rewets the top 8 to 12 inches of root zone (UF/IFAS).
• Remove thatch, which UF/IFAS and NC State both name as chinch bug habitat.

St. Augustine grass problems: symptom, cause and fix

Most failures trace to water, nitrogen or mowing height. This table matches what you see to the likely cause and the fix.

Weeds and herbicide risks

When is St. Augustine grass the wrong choice?

Skip it where the sun drops below 4 hours (and treat 5 to 6 hours, the University of Georgia’s figure for acceptable quality, as the safer minimum), winters kill it, foot traffic is heavy or you won’t irrigate. The grass seed calculator has no St. Augustine entry because no seed exists, but it works out seed pounds for seeded warm-season options such as bermuda, zoysia and centipede grass. For a grass-free yard, the clover lawn guide covers a lawn alternative that it says handles moderate foot traffic. The lawn grass types guide compares all ten common grasses by region and sun.

Frequently asked questions

Can you grow St. Augustine grass from seed?

No. UF/IFAS, NC State and the University of Georgia all say it is planted only as sod, plugs or sprigs.

How far apart should you plant St. Augustine plugs?

6 to 12 inches for faster fill, according to NC State, which does not suggest more than 12 inches on bare ground.

How much sun does St. Augustine grass need?

Clemson says 4 to 6 hours to thrive, the University of Georgia says acceptable quality with as little as 5 to 6 hours of filtered sun, and UF/IFAS says Floratam does not persist on less than 6.

When do chinch bugs attack St. Augustine grass?

Infestations peak in early July, starting in sunny, water-stressed spots. Test with a bottomless coffee can filled with water for five minutes before treating.

Why is my St. Augustine lawn turning yellow?

Yellow, tan or brown patches can come from chinch bugs, large patch or gray leaf spot, and thin, weak turf from nematodes. An overall yellowing can mean a nitrogen shortage, or iron or manganese deficiency on soil above pH 7.0. Iron does not fix a nitrogen shortage, so find the cause with the table above first.

Your next step

Measure the sun where you want to plant, because the 4 to 6 hour range decides everything else. If it passes, buy plugs for a 12-inch grid and plant once daytime temperatures hold above 60°F, NC State’s plug trigger (its sod rule is soil above 55°F for several weeks). Then put the coffee-can test on your July calendar.

Sources

1. Trenholm, L. E., Schiavon, M., Unruh, J. B., Shaddox, T. W., and Kenworthy, K. E. St. Augustinegrass for Florida Lawns (ENH5). UF/IFAS Extension, EDIS, reviewed 2025
2. Bruneau, A. H., et al., eds. Carolina Lawns: A Guide to Maintaining Quality Turf in the Landscape (AG-69). NC State Extension
3. Clemson Cooperative Extension. St. Augustinegrass. Home & Garden Information Center, Clemson University
4. University of Georgia Extension. Lawns in Georgia: Selection and Species (B 1533). University of Georgia
5. Chalmers, D. R., and McAfee, J. Turfgrass Selection for Texas (L-5519). Texas A&M AgriLife Extension
6. Miller, G. St. Augustinegrass. TurfFiles, NC State Extension, updated 2021
7. Gore, A. W. Distinguishing the Difference Between Centipedegrass and St. Augustinegrass. Clemson Cooperative Extension, 2024
8. UF/IFAS Extension. Florida Turfgrass Identification (EP646). EDIS
9. Woods, S. Southern Chinch Bug, Blissus insularis Barber (EENY-226, also numbered IN383). UF/IFAS Extension, EDIS, revised 2024
10. Miller, G., Martin, M., Kerns, J., Brandenburg, R., Billeisen, T., and Yelverton, F. St. Augustinegrass Lawn Maintenance Calendar (AG-540). NC State Extension, 2021
11. NC State Extension. Chinch Bugs in Turf. TurfFiles, NC State University
12. Clemson Cooperative Extension. Brown Patch and Large Patch Diseases of Lawns. Home & Garden Information Center, Clemson University
13. Clemson Cooperative Extension. Gray Leaf Spot on St. Augustinegrass. Home & Garden Information Center, Clemson University