St. Augustine grass (Stenotaphrum secundatum) is among the most desirable warm-season turfgrasses due to its dark green color and dense growth habit. It is well identified by its leaves, sheaths, and growth habit on lawns, golf courses, and pastures.
Homeowner benefits from St. Augustine’s ability to crowd out weeds and resist pests, tolerance to salt and shade, and well-adapted to most soils and different climatic conditions. Proper care and maintenance practices are necessary to keep this turfgrass healthy. Pests (clinch bugs and white grubs ) and diseases (brown patch, gray leaf spot, rust) management practices also come in handy as it is a vulnerable turfgrass, although it stays vibrant throughout the growing season and goes dormant in the winter.
Table of Contents
What Is St. Augustine Grass?
St. Augustine grass is a warm-season grass that goes dormant in winter, native to coastal regions, and tolerates salty conditions.
Here is its taxonomical classification
- Kingdom: Plantae
- Division: Magnoliophyta
- Class: Liliopsida
- Order: Poales
- Family: Poaceae
- Genus: Stenotaphrum
- Species: Stenotaphrum secundatum
St Augustine is vivid blue-green in color, has coarse texture, and thick carpet-like growth habit. The leaf blades are flat, tapered, about 2-4 inches long by 1/4 to 3/4 inches wide. The blades lack auricles and have boat-shaped leaf tips and round, smooth stems that tend to be purple. It has thick-extensive roots and paired seed-head spikes that protrude 3-6 inches above the foliage.
St. Augustine spreads by stolons (above-ground stems), filling bare areas with dense coverage to form a thick mat of thatch due to its vigorous lateral growth.
The most prominent cultivars include Floratam, Palmetto, Delmar, and Sapphire, which vary slightly in color and texture. Proper identification relies on the overall visual and growth characteristics.
According to Richard L. Duble, the first St Augustine purple-colored stigma was found in Cape of Good Hope in 1791 and adopted for the lawn in different parts of the world by 1901. It originated from the coast of the Atlantic Ocean but currently can be found in sand beaches, streams, marshes, lagoons, and swamps all over the world
How to Identify St. Augustine Grass (with pictures)
St. Augustine (Stenotaphrum secundatum) is a warm-season, perennial turfgrass that forms dense turf with a medium-dark green color. You can identify St.Augustine grass by its leaves, flowers, stem, and growth habits/roots. St. Augustine grass cultivators can be distinguished from one another using their key distinctive vegetative and reproductive features.
St. Augustine leaves are medium-to-dark green, uniquely flat, smooth on either side, white midvein, positively arranged on the stolon with a wide round tip. They measure approximately 15-30mm long, 2-4mm wide, and have rounded apexes. St. Augustine leaves are hairless except around the collar region. They lack auricles, and the ligule is a short fringe of hairs about 0.01 inches long. This turfgrass species has folded vernation; the leaves are folded in the bud.
Note: St. Augustine grass gets confused with Centipede and Carpet grass. St Augustine leaves are wide, round, and oppositely arranged, while centipedegrass and carpetgrass leaves are narrow, round, and alternatively arranged.
- Flowers / Seeds
St. Augustine has thick, singular seed heads to produce small-whitish-brown flowers slightly above the leaf blades. The seed head/inflorescence is a single, thick spike with spikelets partly embedded in the rachis. The inflorescence is flat, purple-colored, and 3-5 inches long. Meanwhile, the spikelets are arranged in double rows.
St. Augustine grass sheaths are compressed and hard to pull apart. The sheath margin is open, and the sheath is sparsely hairy along the edges and towards the top. St. Augustinegrass laterally spreads through robust aboveground stems (stolons).
- Growth Habit/Roots
St. Augustine grass lacks rhizomes and spreads laterally via stout stolons (stoloniferous growth habit). These creeping stolons are usually slender and branching. St. Augustine grass spreads relatively slowly due to the lack of rhizomes. However, the roots that develop from the nodes of the stolons are established deep in the soil.
|St Augustine Grass Characteristic||Description|
|Scientific name||Stenotaphrum secundatum|
|Common name||St. Augustinegrass|
|Origin||Coastal regions of Africa and Asia|
|Habitat||Warm, humid environments|
|Growth habit||Perennial, spreading by stolons and rhizomes|
|Leaf blade||Flat, blunt tip, parallel veins|
|Flower||One-sided inflorescence, purplish in color|
|Pros||Tolerates heat, resists disease, and forms a thick mat that prevents weeds|
|Cons||Requires frequent watering, doesn’t grow well in shade, frost-sensitive|
|Uses||Lawns, golf courses, pastures|
|Care||Requires full sun, fertilizes 3-4 times per year, scalp in early spring to remove thatches, irrigate 1-1.5 inches weekly. Propagate by sod, plugs, sprigs. Mow to 2-4 inches in height, avoid excessive traffic, Salt tolerant.|
How to Establish St. Augustine Lawn
St. Augustine lawns are usually established through vegetative means, which include sodding, sprigging, and plugging. Regardless of the establishment method, proper soil preparation is required to successfully establish a healthy St. Augustine grass turf. Start by eliminating all weeds and undesirable grasses using glyphosate.
Then, plow or till the lawn six inches so grassroots can easily penetrate the soil. Level the area and perform a soil test to determine the soil’s fertilizer needs. If you don’t perform a soil test, mix 4-5 pounds of fertilizer into the top 4-6 inches of the soil for every 1000 square feet before planting.
St Augustine Seed
St. Augustine grass doesn’t produce economically viable seeds. Thus, you can only establish a St. Augustine lawn via vegetative propagation. However, the few mature seeds from fertile cultivars may fall, germinate, and establish, resulting in non-true-to-type grass.
St. Augustine Sod
Sodding is the quickest way to establish a new St. Augustine grass lawn, as it provides immediate groundcover, and you don’t have to wait for the turf to fill in. It’s the best method for reducing potential weed competition, as other establishment methods usually leave bare ground. St. Augustine sod typically costs $0.40-$0.75 per square foot.
Lay St. Augustine sod pieces over bare, moist soil in a staggered pattern, as you would when laying bricks. Ensure the ends are fitted tightly together to prevent any open cracks. Once installed, roll and water thoroughly to ensure proper soil contact so the roots quickly develop and extend into the soil. Avoid using the lawn at this stage, as St. Augustine sod is usually vulnerable until the roots are established in the ground.
Sodding can be done all year round but is best done in the spring for warm-season grasses like St. Augustine so that the turfgrass roots can develop before fall and winter frosts.
St. Augustine Sprigs
Sprigging entails planting the plant parts with growing points, which are the nodes of the stolons. The nodes have sections of actively dividing cells that can generate new shoots and root growth.
Plant the runners (stolons) in rows dug 8-12 inches apart to properly establish a St. Augustine grass lawn from sprigs. Every sprig should be a stolon with at least two nodes, planted 4-6 inches apart and 1-2 inches deep. Ensure you leave the leaf blades of each sprig exposed to sunlight and tamp them into place for optimal plant-soil contact.
Note: You can also plant St. Augustine grass sprigs by broadcasting them over the soil before topdressing with ½ an inch of soil.
The best time of the year to plant St. Augustine sprigs is in the late spring and early summer when temperatures are moderate.
St. Augustine Plugs
You can also establish a St. Augustine lawn by plugging. You can buy plugs directly from garden centers or make them yourself by cutting sod pieces into tiny, 2×2-inch squares. A 16-pack size of Floratam St. Augustine grass plugs costs roughly $40-$50.
Plant the plugs in similar-sized holes and tamp them into place. Plugs are typically spaced 6-24 inches apart, with the closer spacing providing faster ground cover to counter weed invasion. After installing the grass plugs, deeply water the turf so the soil is thoroughly saturated.
After that, ensure the soil stays moist but not waterlogged until new growth appears. Once there’s new growth, start mowing to a height of 2 inches. Only cut when the soil/grass isn’t wet, and ensure you use sharp mower blades to avoid damaging the grass blades.
Plant St. Augustine plugs from late spring to early summer when there is high rainfall to aid in faster turf establishment. Avoid planting during the drier months in the late summer.
Note: The mutations may occur in vegetatively propagated turf that may result in new traits.
Care and Maintenance for St. Augustine Grass Lawn
Here is a summary of St. Augustine grass’s characteristics, care, and maintenance practices.
- Soil: Best on slightly acidic to neutral, ideally around 6.5 to 7.0 soil pH. Grass thrives in various soil types with moderate fertility and good drainage.
- Sunlight: Tolerate moderate shade, though best for full sun.
- Water: Deeply water 1-2 times a week in warmer sessions to prevent stress; rainfall may provide adequate water for healthy growth.
- Mowing: Mow to 2.5 to 3 inches routinely in the growing season, but avoid removing a third of leaf blade height in one mowing routine.
- Tolerance: Different cultivators have different tolerance. Generally, it has good shade, heat, and humidity tolerance. St. Augustine has moderate to amazing injury recovery, depending on the cultivator selected.
- Fertilization: best apply slow-release fertilizer in mid-spring to mid-summer, 3 pounds of nitrogen per 1,000 square feet per year.
- Dethatching and Aeration:
- Establishment: Majorly done through plugs and sod, but can also be established with seeds.
- Growth Rate: Tends to Spread quickly via stolons forming mat-like lawns.
Soil pH levels determine nutrient availability. Correct the nutrient deficiencies after taking a soil test and being aware of the soil pH. St. Augustine grass struggles in iron-deficient soil, and the grass leaves usually turn yellow in low-iron soil with an alkaline pH greater than 7.5.
- Apply iron sulfate or iron chelate to correct this problem. When amending soil micronutrient needs in alkaline soils, avoid soil application of granular iron, as the iron usually binds up quickly and can’t be absorbed by plants.
Note: You can add micronutrients to your St. Augustine turf by applying high-quality compost.
Meanwhile, soil cultivation is necessary to address soil compaction and excessive thatch accumulation. However, this practice also causes turfgrass injury. You should, therefore, cultivate your St. Augustine lawn when it’s actively growing in the spring and early summer for faster recovery. Proper irrigation and fertilization after cultivation will also speed up the recovery rate.
After cultivation, the de-compacted soil allows for better water infiltration to promote root growth. The cultivated turf also limits the thatch layer below 0.5 inches, thus reducing turfgrass pest activity and giving the turf a better texture.
St. Augustine grass isn’t as drought-hardy as other common warm-season grasses and, thus, requires supplemental watering throughout the growing season for the turf to stay healthy. Deeply water your St. Augustine lawn 1-2 times per week during the warmer months. This deep and infrequent watering schedule ensures that the turf develops deep and healthy roots that can withstand heat and drought stress.
The best time to irrigate St. Augustine grass is early morning (3 a.m.- 9 a.m.) to minimize evaporative losses. Evening irrigation isn’t recommended, as the grass leaves stay wet for longer, thus encouraging disease infection.
St. Augustine grass is the most shade-tolerant warm-season turfgrass and will survive in partial to moderate shade. It requires 4-6 hours of sunlight per day to survive. However, grow St. Augustine in full sun for the best turf density and color appearance.
Additionally, this turfgrass responds better to afternoon light than to morning light. Despite its good shade tolerance, St. Augustine grass may not survive in heavily shaded areas, such as under dense canopies.
A balanced fertilizer schedule is crucial for developing and sustaining a healthy St. Augustine lawn. After taking a soil test and determining the fertilizer requirements of your lawn, apply nutrients based on the soil test results, except for nitrogen, which should be applied depending on the soil type, cultivar, and the desired response. The soil test results also contain information regarding the soil pH level.
Generally, a St. Augustine turf requires 1-4 pounds of nitrogen fertilizer per 1000 square feet annually to maintain a healthy appearance. The first fertilizer application should be made after the lawn has been mowed twice in the spring since, at this stage, there’s new growth, and the grass can take up the nitrogen nutrients from the soil.
Meanwhile, the final fertilizer application should be done 4-6 weeks before the first frost date in the fall. Applying fertilizer any later leads to fall over-application, which then causes winter kill and winter diseases.
When applying fertilizer products on St. Augustine grass, follow the manufacturer’s recommended application rates to prevent fertilizer burn. The recommended application rate for quick-release nitrogen is 0.5-1 pound of nitrogen per 1000 square feet in a single application. Higher rates are usually recommended for slow-release nitrogen products.
Adopt proper mowing practices to keep St. Augustine grass healthy and looking nice. Mow the lawn weekly during the growing season and reduce the mowing frequency during the cooler months. Keep the mower blades sharp for a clean cut that won’t shred the leaf blades and leave a brown cast. Sharpen the blades at least once every four weeks during the growing season.
Mow at a height of 3.5-4 inches to encourage deeper rooting and better turfgrass appearance. If you mow St. Augustine grass at a lower height, your turfgrass won’t root deeply, and the lawn will be more susceptible to scalping and pest problems. However, for dwarf St. Augustine grass varieties, the recommended mowing height is 2-2.5 inches.
Avoid removing more than ⅓ of the leaf blades when mowing your St. Augustine lawn. Also, we recommend increasing the mowing height if the turf is experiencing moisture stress or is growing in the shade. Finally, avoid infrequent mowing and mowing too high, which will cause thatch buildup.
Once you’ve mowed your St. Augustine lawn at the right height, leave the grass clippings to return nutrients and organic matter to the soil.
It’s important to aerate St. Augustine grass to alleviate soil compaction. Aeration generates channels in the root zone for better air and water penetration, creating more space for root expansion. This practice is best done before applying fertilizer, top dressing, or compost to optimally incorporate these materials into the soil.
The most effective aeration method is called core aerification, whereby a core aerifier removes plugs of soil to alleviate compaction. Core aerifiers are usually available for rent and typically penetrate the soil to a depth of 4 inches, enough to relieve compaction.
Note: Cultivation practices like aeration and dethatching shouldn’t be carried out during periods of extreme weather, such as when it’s frosty, during drought, and when there’s high heat.
Dethatching turfgrass helps alleviate thatch buildup and soil compaction. The best method for dethatching a St. Augustine grass turf is verticutting, whereby a vertical mower slices into the turf to remove the built-up thatch. St. Augustine grass is relatively coarse; thus, space the mower blades 3 inches apart to verticut it without applying too much effort. Also, ensure the blades are sharpened to avoid snagging and uprooting the turf.
Once you’re done, remove the lifted thatch debris using a pitchfork and a wheelbarrow. Verticutting is not only used for dethatching but also to stimulate new growth. New growth is generated as the mower blades slice vertically through the St. Augustine stolons.
Overseed St. Augustine grass in the fall using a cool season turfgrass such as perennial ryegrass to maintain the lawn’s appearance during winter. It also protects the dominant warm-season grass (St.Augustine) from wear and tear during heavy traffic.
You can also overseed with annual ryegrass, but perennial ryegrass dies out quicker in the spring, allowing the permanent St. Augustine turf to emerge. Before overseeding, apply a 12-12-12 fertilizer to avail enough phosphorus for root development. Then, plant perennial ryegrass seeds at a rate of 5-7 pounds per 1000 square feet. After seeding, water the lawn daily until ryegrass seedlings begin to grow.
Note: Don’t overseed a St. Augustine turf growing in moderate-heavy shade, as the cool season grass will linger into summer and prevent the dormant St. Augustine grass from reemerging.
The best way to control weeds is to maintain a healthy, vigorous St. Augustine turf. However, if weeds persist despite proper management practices, apply a pre- or post-emergent herbicide formulated for use on St. Augustine grass.
Pre-emergents like pendimethalin effectively prevent crabgrass’s emergence on St. Augustine turfs. Meanwhile, post-emergents like Atrazine effectively kill broadleaf weeds like chickweed and henbit.
Note: Avoid using ‘weed-n-feed’ products on turfgrasses like St. Augustine grass, whose roots extend deep into the soil due to the high potential for damage.
Varieties/ Types of St. Augustine Grass
Here are different types of St Augustine grass:
- Bitterblue– a dense-textured cultivar with excellent shade and cold tolerance.
- Classic– a standard variety with good cold tolerance and a beautiful dark green color.
- Floratam– a coarse-textured cultivar with relatively poor cold and shade tolerance.
- Palmetto– a semi-dwarf type with a lighter shade of green.
- Raleigh– a cold-tolerant, coarse-textured cultivar with a medium green shade.
- Seville- a dwarf St. Augustine variety that does well in shady sites but is susceptible to thatch buildup.
- Provista– a low-maintenance variety that provides dense ground cover.
- CitraBlue– a blue-green colored cultivar with good weed and disease resistance.
St. Augustine grass is vulnerable to chinch bugs and white grubs. Chinch bugs typically invade this turfgrass in the heat of the summer and feed on the plant sap, resulting in irregular patches and dead grass. You can minimize chinch bug damage by repeatedly applying an insecticidal treatment.
White grubs, on the other hand, are larval pests that feed on the roots of St. Augustine grass, resulting in root rot and dead turfgrass. These pests typically invade the turf from late May to July. Preventative chemical treatment is recommended.
The most common diseases on St. Augustine grass are gray leaf spots, large patches, and take-all root rot.
- Gray leaf spot – is a summer disease that causes gray lesions and leaves withering. To prevent this disease from spreading, ensure you remove and bag grass clippings after mowing.
- Large patch– a spring and fall disease that causes circular patches with yellow edges on the leaves. You can control this disease using appropriate fungicides or cultural management practices like drainage and thatch removal.
- Take-all root rot– a fungal infection most apparent when St. Augustine is coming out of dormancy in the spring. It causes the turfgrass to thin out and develop brown patches. Take-all root rot can be controlled using cultural management practices like proper irrigation and balanced fertilization.
Other Problems Associated with St. Augustine Grass
- Excess shade- prevents the turf from developing a lush, dark green color.
- Compacted soil- prevents water and air infiltration into the root zone.
- Overwatering- causes root rot.
- Underwatering- causes drought stress.
- Improper mowing- causes turfgrass physical injury.
- High pH- causes leaf chlorosis.
- Traffic- causes soil compaction.
The life cycle of St. Augustine grass
St. Augustine grass is a warm-season turfgrass that goes dormant in the cold winter and reemerges in the spring after the last frost. The dates when it goes dormant or reemerges vary slightly depending on the region.
I. North Carolina State University (NCSU) Extension: St. Augustine Grass