St. Augustine Grass Care Guide

St. Augustine grass thrives with weekly deep watering, monthly fertilization during growing season, and mowing at 3-4 inches height. This warm-season grass demands consistent moisture (about 1-1.5 inches per week), proper pH between 6.0-6.5, and regular pest monitoring. St. Augustine performs best in full sun but tolerates moderate shade better than most warm-season grasses.

What Makes St. Augustine Grass Different?

St. Augustine grass stands out among warm-season grasses for its exceptional shade tolerance and aggressive spreading habit through above-ground stolons. Unlike Bermuda or Zoysia, St. Augustine can maintain decent density with only 4-6 hours of direct sunlight daily. Those wide, flat blades create a thick, carpet-like lawn when properly maintained.

This grass originated in the coastal regions of the Gulf of Mexico and absolutely loves humid, subtropical climates. St. Augustine goes dormant when temperatures consistently drop below 50°F and takes serious damage at 25°F or lower. The grass actively grows from late spring through early fall in most regions.

Which St. Augustine Variety Should You Choose?

Floratam dominates the St. Augustine market due to its chinch bug resistance and heat tolerance. This variety demands full sun and struggles in shaded areas, making it ideal for open lawns in hot climates. Floratam holds its green color longer into fall compared to other varieties.

Palmetto offers superior cold tolerance and shade performance, surviving temperatures down to 5°F when properly established. This variety works well in transitional zones where winter temperatures occasionally dip below St. Augustine’s normal range. Palmetto also shows better drought tolerance than standard varieties.

Raleigh performs well in partially shaded areas and shows good cold tolerance, making it popular in North Carolina, Tennessee, and northern regions of St. Augustine’s range. This variety produces a finer texture than Floratam but spreads more slowly, patience is key here.

How Should You Water St. Augustine Grass?

Water St. Augustine grass deeply but infrequently, aim for 1-1.5 inches per week including rainfall. Apply water in one or two sessions rather than daily light sprinklings, which encourage shallow roots and invite disease problems. The grass tells you when it needs water: blue-gray color and footprints that stay visible on the turf.

Water early morning between 6-10 AM to minimize evaporation and reduce disease pressure from prolonged leaf wetness. Skip evening watering, wet grass blades overnight create perfect conditions for brown patch and other fungal diseases.

St. Augustine’s shallow root system makes it thirstier than other warm-season grasses. During peak summer heat, you might need to bump up watering frequency to 2-3 times per week while keeping the same total weekly amount. Clay soils need less frequent but longer sessions, while sandy soils demand more frequent applications.

What’s the Proper Mowing Height for St. Augustine?

Keep St. Augustine grass at 3-4 inches height during active growing season. Higher mowing heights improve shade tolerance, reduce weed pressure, and help the grass handle heat stress. Never hack off more than one-third of the blade length in a single mowing session, that’s lawn care 101.

Mow when the grass reaches 4.5-5 inches, cutting back to 3-3.5 inches. Sharp mower blades are non-negotiable here. Dull blades create ragged cuts that turn brown and increase disease problems. Replace or sharpen mower blades at least twice per season, your grass will thank you.

During fall transition, gradually lower cutting height to 2.5-3 inches to reduce winter disease risk in northern areas. Resume higher cutting heights as soon as active growth begins in spring.

Bag clippings when they’re excessive (more than 1 inch long) to prevent thatch buildup. Otherwise, leave them on the lawn, they decompose quickly and provide valuable nitrogen, up to 25% of the lawn’s annual nitrogen needs according to University of Florida research.

How Do You Fertilize St. Augustine Grass?

Feed St. Augustine 3-4 pounds of nitrogen per 1,000 square feet annually, split into monthly applications from April through September. Use a fertilizer with a 3-1-2 or 4-1-2 ratio (nitrogen-phosphorus-potassium) for established lawns. Each monthly feeding should deliver 0.5-1 pound of nitrogen per 1,000 square feet.

Get a soil test to determine phosphorus and potassium needs, most established St. Augustine lawns need little to no phosphorus. The University of Georgia Extension recommends soil testing every 2-3 years to avoid phosphorus overload, which ties up iron and causes yellowing.

Apply iron supplements 2-3 times per growing season if your soil pH climbs above 7.0. St. Augustine shows iron deficiency as interveinal chlorosis (yellow leaves with green veins), especially common in alkaline soils. Chelated iron works best for treatment.

What Soil Conditions Does St. Augustine Need?

St. Augustine performs best in slightly acidic soil with pH between 6.0-6.5. At this sweet spot, nutrients stay available and disease pressure remains minimal. Soil pH above 7.5 causes iron chlorosis, while pH below 5.5 increases aluminum toxicity and reduces calcium availability.

The grass tolerates various soil types but thrives in well-draining soil with good organic matter content. Heavy clay needs amendment with compost or sand to improve drainage, while sandy soils benefit from organic matter to boost water retention. Poor drainage leads to root rot and fungal disease problems.

Apply lime to raise pH or sulfur to lower pH based on soil test results. Lime works slowly, expect 6-12 months for full effect. Sulfur acts faster but needs careful application since over-application can damage grass roots.

How Do You Control Weeds in St. Augustine?

Dense, healthy St. Augustine naturally suppresses most weeds through aggressive spreading and shade production. Keep up proper fertility and watering to encourage thick growth that crowds out weed seedlings. Weak or thin areas roll out the welcome mat for weeds.

Apply pre-emergent herbicides in early spring (February-March) before soil temperatures hit 65°F consistently. Atrazine works effectively for both pre- and post-emergent weed control in St. Augustine but can cause yellowing if you go heavy-handed. Stick to label rates religiously.

Hand-pull large weeds during wet conditions when soil is soft. For broadleaf weeds like dandelions and clover, spot-treat with 2,4-D based herbicides. Skip products containing 2,4-D when temperatures climb above 85°F, St. Augustine gets touchy with these chemicals in hot weather.

From our experience, the most problematic weeds in St. Augustine include:

• Dollar weed (thrives in overwatered lawns)
• Crabgrass (prevented with proper pre-emergent timing)
• Clover (indicates low nitrogen levels)
• Dandelions (common in thin areas)

What Diseases Affect St. Augustine Grass?

Brown patch represents the most serious fungal threat in St. Augustine lawns, appearing as circular brown patches 6 inches to several feet in diameter. This disease loves humid conditions with nighttime temperatures above 68°F and excessive nitrogen fertilization. Symptoms include dark, water-soaked leaf lesions that quickly turn brown.

Gray leaf spot creates small, oval lesions with dark brown borders and gray centers on individual grass blades. High humidity, excessive nitrogen, and poor air circulation promote this disease. Unlike brown patch, gray leaf spot targets individual leaves rather than creating distinct circular patterns.

Large patch (formerly known as Rhizoctonia brown patch) strikes during cool, wet weather in fall and spring. This disease creates irregularly shaped brown areas that can reach 20+ feet in diameter. Affected areas often show a dark brown margin where the disease actively spreads.

Prevention strategies include:

• Improve air circulation by pruning nearby shrubs
• Water early morning to reduce leaf wetness duration
• Avoid over-fertilizing with quick-release nitrogen
• Maintain proper soil pH and drainage
• Remove excessive thatch buildup

How Do You Manage Common St. Augustine Pests?

Chinch bugs cause the most significant pest damage in St. Augustine lawns, creating irregular brown patches that spread outward from sunny areas. These tiny insects (1/6 inch long) suck plant juices and inject toxins that kill grass. Damage shows up first along driveways, sidewalks, and other heat-reflective surfaces.

Check for chinch bugs by parting the grass at the edge of damaged areas and looking for small black insects with white wings. You can also use the flotation method: push a coffee can with both ends removed into the soil and fill with water. Chinch bugs will float to the surface within 10 minutes.

Treat chinch bug infestations with bifenthrin or carbaryl applications, following label directions carefully. Applications work best when applied to moist soil and watered in lightly. Beneficial insects like big-eyed bugs naturally control chinch bug populations when pesticide use stays minimal.

Sod webworms create small brown spots and chew grass blades at soil level. Look for green pellet-like droppings and small moths flying over the lawn at dusk. Light infestations rarely need treatment in healthy lawns.

When Should You Dethatch St. Augustine?

Dethatch St. Augustine when the thatch layer exceeds 0.5 inches thickness. This typically happens every 2-3 years in well-maintained lawns or annually in heavily fertilized areas. Test thatch depth by cutting a small wedge of turf and measuring the brown layer between green grass and soil surface.

Dethatch during active growing season (May-July) when grass can bounce back quickly from the stress. Use a vertical mower (verticutter) set to penetrate slightly into the soil surface. Make passes in two directions perpendicular to each other for thorough thatch removal.

Excessive thatch creates several problems:

• Blocks water and fertilizer penetration
• Harbors insects and disease organisms
• Creates shallow root systems
• Increases scalping risk during mowing

Follow dethatching with light topdressing of compost and overseeding in thin areas. Water regularly for 2-3 weeks while the lawn recovers. Keep foot traffic light during the recovery period.

How Do You Overseed St. Augustine Grass?

St. Augustine doesn’t produce viable seed, so establishment and repair demand vegetative methods using sod, plugs, or stolons. Sod provides instant coverage but costs significantly more than other options. Plugs offer a middle-ground approach, while stolons provide the most economical option for large areas.

Plant plugs 12-18 inches apart in a checkerboard pattern for fastest coverage. Closer spacing (6-12 inches) fills in faster but increases cost. Dig holes slightly larger than the plug and ensure good soil contact around roots. Water immediately after installation and maintain consistent moisture for 2-3 weeks.

Stolon sprigging works well for large areas but demands more patience for establishment. Spread stolons evenly over prepared soil and cover lightly with soil or compost. Press stolons into soil contact using a roller. This method typically takes 8-12 weeks for complete coverage under ideal conditions.

Best planting times vary by region:

• Deep South: March-September
• Central regions: April-August
• Northern areas: May-July

What’s the Seasonal Care Schedule for St. Augustine?

Spring care begins with removing winter debris and gradually resuming regular watering as grass breaks dormancy. Apply pre-emergent herbicide when soil temperatures reach 55-60°F consistently. Begin monthly fertilization when grass shows active growth, typically mid-April in most regions.

Summer maintenance focuses on consistent watering, regular mowing, and pest monitoring. Increase watering frequency during heat stress periods while maintaining total weekly amounts. Watch for chinch bug damage in sunny areas and brown patch development during humid periods.

Fall preparation includes reducing fertilization rates and gradually lowering mowing heights. Apply final fertilizer application in September with reduced nitrogen content. Continue regular watering until grass enters dormancy. Handle any needed overseeding or renovation work during early fall.

Winter care in northern areas may include light fertilization if grass remains semi-active. Avoid foot traffic on frozen grass to prevent damage. Plan spring renovation projects and order materials during winter months.