St Augustine Grass Florida: The Ultimate Seasonal Care Calendar

The Florida Microclimate Divide: North vs. South

Managing St Augustine grass in Florida requires abandoning the idea of a single, statewide schedule. Florida spans USDA Hardiness Zones 8b through 11, creating distinct microclimates that dictate turfgrass behavior. North Florida (Panhandle to Jacksonville) experiences winter frost and true dormancy, while Central and South Florida (Orlando to the Keys) maintain active, albeit slowed, growth year-round.

As of 2026, the dominant cultivars planted across the state include Floratam (the legacy standard), Palmetto (for partial shade), and CitraBlue (the UF/IFAS release that has rapidly overtaken Floratam in new commercial installations due to superior shade tolerance and drought resistance). Your seasonal calendar must adapt not just to your latitude, but to your specific cultivar's genetic thresholds.

Spring Awakening: Breaking Dormancy (March – May)

Spring is the most critical window for St Augustinegrass. The goal is to stimulate stolon growth without triggering gray leaf spot (Pyricularia grisea) or pushing tender new growth into a late freeze.

Pre-Emergent and Fertilization Timing

Do not fertilize St Augustine in Florida until the lawn has fully greened up and you have mowed it twice. Applying nitrogen to dormant or semi-dormant roots invites large patch fungus (Rhizoctonia solani).

• North Florida: Apply pre-emergent (prodiamine 65 WDG at 1.5 lbs per 1,000 sq ft) by February 28. Fertilize no earlier than April 15.
• Central Florida: Pre-emergent by February 15. Fertilize by March 20.
• South Florida: Pre-emergent by January 30. Fertilize by March 1.

According to the UF/IFAS St. Augustinegrass guidelines, slow-release nitrogen sources are mandatory in spring to prevent rapid flush growth that attracts southern chinch bugs later in the season.

Summer Survival: Heat, Humidity, and Blackouts (June – August)

Florida summers subject St Augustine to extreme physiological stress. High nighttime temperatures (above 75°F) combined with 90% humidity create a breeding ground for fungal pathogens, while the sandy soils drain rapidly under intense sun.

The Urban Fertilizer Blackout

Most Florida counties enforce a strict fertilizer blackout period from June 1 through September 30. During this window, the application of nitrogen and phosphorus is illegal to prevent aquatic nutrient loading. You can, however, apply Potassium (K) and micronutrients.

Summer Mowing and Irrigation Specs

Mow Floratam at 3.5 to 4.0 inches and CitraBlue at 2.5 to 3.0 inches. Lower mowing heights in summer expose the soil to UV radiation, increasing evaporation and inviting weed invasion. Calibrate your sprinkler system to deliver exactly 0.5 to 0.75 inches of water per irrigation event, running only when the grass blades fold in half (a sign of wilting). The Florida Department of Environmental Protection strictly monitors summer runoff, making precise irrigation calibration both an ecological and legal necessity.

Fall Transition: Disease Prevention (September – November)

Fall in Florida is deceptive. Air temperatures drop, but soil temperatures remain warm, creating the exact environmental parameters for Large Patch (Rhizoctonia solani). This disease attacks the leaf sheaths at the base of the plant, causing circular, sunken, brown patches that can expand to 10 feet in diameter.

Winterizer Misconceptions

Do not apply high-nitrogen "winterizer" fertilizers to St Augustine in Florida. Pushing late-season vegetative growth depletes the plant's carbohydrate reserves right before winter. Instead, focus on potassium and preventative fungicides.

1. October 1-15: Apply a preventative fungicide containing azoxystrobin (Heritage G) or propiconazole (Banner Maxx) at the preventative label rate.
2. November: Apply 1.0 lb of Potassium (K2O) per 1,000 sq ft using a 0-0-22 or similar N-free formulation to harden the stolons against frost.
3. Late November: Raise your mower deck by 0.5 inches to allow the canopy to insulate the crown during cold snaps.

Winter Dormancy: Weed Control (December – February)

In North and Central Florida, St Augustine will turn brown or purple and enter dormancy. South Florida lawns may only slow their growth. This is the optimal time to tackle broadleaf weeds and annual grassy weeds without risking chemical burn to the active St Augustine turf.

Herbicide Selection for Dormant Turf

Avoid herbicides containing 2,4-D when daytime temperatures exceed 85°F, but winter provides a safe window. For tough broadleaf weeds like dollarweed and Virginia buttonweed, use a product containing metsulfuron-methyl (Blindside). It is highly effective at low temperatures and safe for St Augustine when applied at 0.25 oz per acre. For annual bluegrass (Poa annua), spot-treat with atrazine, ensuring you do not exceed 1.5 pints per acre per application to prevent root stunting.

Regional Month-by-Month Quick Reference Matrix

Use this matrix to cross-reference your specific Florida region with the required monthly maintenance tasks.

Common Timing Mistakes That Kill Florida St Augustine

Even experienced homeowners make fatal errors when treating St Augustinegrass. Avoid these specific failure modes:

• Overwatering in Winter: St Augustine requires 70% less water during December and January. Running summer irrigation schedules in winter saturates the sandy soil, suffocating roots and triggering Pythium root rot.
• Scalping in Spring: Never "scalp" St Augustine down to the dirt in spring to remove brown winter blades. Unlike Bermudagrass, St Augustine stores its energy in above-ground stolons. Scalping removes the plant's energy reserves, leading to severe thinning and weed invasion. Instead, mow at your normal height and bag the clippings to remove the brown tips.
• Ignoring Soil pH: Florida's native soils and fill sands often have a pH above 7.0. At high pH, iron and manganese become locked out, causing severe yellowing regardless of how much nitrogen you apply. If your soil pH is above 7.2, apply elemental sulfur at 1 lb per 1,000 sq ft in the fall, or rely entirely on foliar chelated micronutrient sprays during the growing season.

Expert Insight: The transition from Floratam to CitraBlue is changing mowing dynamics in Florida. Because CitraBlue has a denser, more upright growth habit and shorter internodes, it tolerates lower mowing heights (2.5 inches) compared to Floratam's sprawling 4-inch requirement. Adjust your mower deck based on your specific cultivar, not generic St Augustine advice.