Grass Types
A Field Guide to Identifying Types of St. Augustine Grass Cultivars
The Genetic Landscape of St. Augustine Grass
St. Augustinegrass (Stenotaphrum secundatum) is the dominant warm-season turfgrass in USDA hardiness zones 8 through 10, prized for its rapid establishment and salt tolerance. However, referring to "St. Augustine" as a single entity is a critical agronomic error. The species comprises numerous distinct cultivars, each engineered or selected for specific microclimates, pest pressures, and light conditions. Misidentifying your current turf or selecting the wrong cultivar for your property's light profile is the primary cause of lawn failure in coastal and southern landscapes.
According to the University of Florida Turfgrass Science program, modern St. Augustine breeding focuses heavily on overcoming historical vulnerabilities, specifically the St. Augustine Decline (SAD) virus and southern chinch bug (Blissus insularis) biotypes. Understanding the morphological differences between the major types of St. Augustine grass is essential for proper maintenance, mowing height calibration, and targeted pest management.
Visual Identification Matrix: Spotting the Differences
Field identification relies on three primary morphological markers: leaf blade width, stolon (runner) diameter, and canopy coloration. The table below provides exact measurements for the five most commercially available cultivars in 2026.
| Cultivar | Leaf Blade Width | Stolon Diameter | Canopy Color | Texture Profile |
|---|---|---|---|---|
| Floratam | 10 - 12 mm | 4 - 5 mm (Thick) | Medium Green | Very Coarse |
| CitraBlue | 8 - 9 mm | 3 - 4 mm | Blue-Green | Medium-Coarse |
| Palmetto | 7 - 8 mm | 3 - 4 mm | Dark Emerald Green | Medium-Fine |
| Bitter Blue | 8 - 9 mm | 3 - 4 mm | Blue-Green | Medium |
| Seville | 5 - 6 mm | 2 - 3 mm (Thin) | Dark Green | Fine / Dwarf |
Top Cultivars Explained: Traits, Tolerances, and Costs
Floratam: The Coarse-Textured Industry Standard
Released in 1972 by the University of Florida and Texas A&M, Floratam remains the most widely planted St. Augustine cultivar by total acreage. It is easily identified by its exceptionally wide leaf blades (often exceeding 10mm) and thick, purple-tinged stolons. Floratam requires a minimum of 6 to 8 hours of direct, unfiltered sunlight daily. While it was originally bred for resistance to the SAD virus and the southern chinch bug, Texas A&M AgriLife Extension notes that localized chinch bug biotypes have largely overcome Floratam's genetic resistance, requiring proactive insecticide rotations (such as bifenthrin alternated with clothianidin) in high-pressure zones.
- Optimal Mowing Height: 3.5 to 4.0 inches
- 2026 Sod Pricing: $0.55 to $0.75 per square foot
- Primary Weakness: Severe shade intolerance; rapid thatch accumulation.
CitraBlue: The Modern Disease-Resistant Challenger
Developed by the University of Florida and released to the commercial market around 2020, CitraBlue (cultivar 'FSA1602') has rapidly captured market share from Floratam. It is identified by a distinct blue-green hue and a slightly finer leaf texture than Floratam. Its primary agronomic advantage is superior resistance to gray leaf spot (Pyricularia grisea) and large patch (Rhizoctonia solani), drastically reducing the need for preventative fall fungicide applications. CitraBlue also exhibits a denser growth habit, which naturally suppresses weed invasion during the establishment phase.
- Optimal Mowing Height: 2.5 to 3.5 inches
- 2026 Sod Pricing: $0.85 to $1.10 per square foot
- Primary Weakness: Higher upfront establishment cost; limited availability in northern transition zones.
Palmetto & Seville: The Fine-Leaf Shade Specialists
When properties feature heavy canopy cover from live oaks or pines, broad-leaf cultivars like Floratam will inevitably thin and fail. Palmetto and Seville are the standard solutions for shaded environments. Palmetto features a darker emerald green color and can survive on 3 to 4 hours of filtered sunlight. Seville is a dwarf cultivar with the finest leaf texture of the group, allowing it to be mowed as low as 2.0 inches, though it suffers from poor cold hardiness and will experience severe winter kill if temperatures drop below 25°F for extended periods. Both cultivars are highly susceptible to chinch bug damage and require strict moisture management to avoid fungal pathogens in low-light conditions.
⚠️ CRITICAL WARNING: St. Augustine Decline (SAD) Virus
If you are identifying an existing lawn that exhibits yellow mottling on the leaf blades and a general failure to thrive despite adequate fertilization, suspect the SAD virus. Older, unimproved types of St. Augustine and the cultivar 'Raleigh' are highly susceptible. There is no chemical cure for SAD. If confirmed via tissue testing, the only remediation is complete eradication and replanting with a certified SAD-resistant cultivar like Floratam, Palmetto, or CitraBlue.
Environmental Stress Tolerance Comparison
Selecting the correct cultivar requires matching the grass's genetic thresholds to your property's specific environmental stressors. NC State TurfFiles provides baseline data for transition zone plantings, emphasizing that cold hardiness is the limiting factor for St. Augustinegrass expansion.
- Cold Hardiness: Bitter Blue > Floratam > Palmetto > CitraBlue > Seville. (Bitter Blue can survive brief dips into the low 20s°F, making it the preferred choice for the northern edges of Zone 8).
- Shade Tolerance: Seville > Palmetto > CitraBlue > Bitter Blue > Floratam. (Seville can maintain density with as little as 2.5 hours of dappled sunlight).
- Drought Recovery: Floratam > CitraBlue > Bitter Blue > Palmetto > Seville. (Floratam's massive stolon network allows it to recover from dormancy faster than fine-leaf varieties once irrigation resumes).
- Salinity Tolerance: All St. Augustine types tolerate salt spray well, but Floratam and CitraBlue exhibit the best recovery rates in coastal soils with electrical conductivity (EC) levels up to 16 dS/m.
Microclimate Decision Framework
Use this step-by-step framework to determine which type of St. Augustine grass to install or overseed (via plugs) in your landscape:
- Map Your Sunlight: Track direct sunlight hours in mid-July. If the area receives 6+ hours, plant Floratam or CitraBlue. If it receives 3 to 5 hours, plant Palmetto. If it receives under 3 hours, abandon St. Augustine entirely and consider shade-tolerant groundcovers or mulch beds.
- Assess Pest History: If your neighborhood has a documented history of severe chinch bug infestations, avoid Seville and Palmetto. Invest in CitraBlue and implement a preventative systemic insecticide program in May.
- Evaluate Winter Extremes: If you live in the northern panhandle of Florida, coastal Georgia, or the Carolinas (Zone 8a/8b), prioritize Bitter Blue or Raleigh (if SAD is not present in your county) to prevent catastrophic winterkill.
- Calculate Budget: For large properties over 5,000 sq ft, Floratam's lower per-square-foot cost ($0.65 avg) saves thousands upfront compared to CitraBlue ($0.95 avg), though CitraBlue may offset this via reduced fungicide and water costs over a 5-year period.
Frequently Asked Questions
Can I mix different types of St. Augustine in the same lawn?
No. Mixing cultivars (e.g., plugging Palmetto into an existing Floratam lawn) results in a visually fragmented canopy. Because the cultivars have different optimal mowing heights, growth rates, and color profiles, one will inevitably outcompete the other or create distinct textural zones that look like weed patches. Always identify the dominant existing cultivar and match it exactly for repairs.
How do I identify SAD virus versus iron chlorosis?
Iron chlorosis typically presents as uniform yellowing of the youngest leaves while the veins remain green, often occurring in high-pH soils. The SAD virus presents as a distinct, uneven yellow mottling or stippling across the entire leaf blade, affecting both old and new growth. A soil test for pH and a tissue test for the panicum mosaic virus are required for definitive diagnosis.
Which St. Augustine type requires the least water?
While no St. Augustine grass is considered truly drought-tolerant compared to Zoysia or Bermuda, CitraBlue has demonstrated superior water retention and deeper root mass development in recent university trials, allowing it to maintain turgor pressure longer during scheduled irrigation deficits than older cultivars like Floratam.
