St. Augustine grass differs from Bermuda and Zoysia in three ways that affect fertilizer selection: it tolerates shade (and often grows under tree canopy where soil pH drifts higher and iron becomes less available), it has lower drought tolerance (so high-nitrogen summer pushing can stress the grass), and it is sensitive to atrazine — an herbicide found in some weed-and-feed products. At 6BC Botanical Garden, iron deficiency is the most common St. Augustine complaint we encounter, and in nearly every case the root cause is high soil pH locking out existing iron rather than an actual iron shortage in the soil.
| St. Augustine Liquid Grass Fertilizer – 1 Gallon |  |
Best for Consistent Green | Targeted for St. Augustine: Formulated specifically for St. Augustine grass | Product Form: Liquid | Primary Use: Lawn food / fertilizer for turf health and color | VIEW LATEST PRICE | Read Our Analysis |
| Scotts Green Max Lawn Food with Iron Supplement |  |
Fast Greening Boost | Targeted for St. Augustine: Suitable for any grass type (includes St. Augustine) | Product Form: Granules | Primary Use: Lawn food with iron for feeding and greening | VIEW LATEST PRICE | Read Our Analysis |
| St. Augustine Liquid Grass Fertilizer – 8 oz |  |
Concentrated Spot Treatment | Targeted for St. Augustine: Formulated specifically for St. Augustine grass | Product Form: Liquid | Primary Use: Lawn food / fertilizer for turf health and color | VIEW LATEST PRICE | Read Our Analysis |
| Sunniland Weed & Feed for St. Augustine Grass |  |
Weed Control Combo | Targeted for St. Augustine: Designed for St. Augustine grasses | Product Form: Granules | Primary Use: Weed & feed (fertilizer plus weed control) | VIEW LATEST PRICE | Read Our Analysis |
| Andersons Professional PGF 16-4-8 Fertilizer (5,000 sq ft) |  |
Professional Performance | Targeted for St. Augustine: Intended for lawn grasses including St. Augustine | Product Form: Super-fine granules | Primary Use: Complete turf fertilizer and soil conditioning | VIEW LATEST PRICE | Read Our Analysis |
More Details on Our Top Picks
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St. Augustine Liquid Grass Fertilizer – 1 Gallon
Best for Consistent Green
Our Take: St. Augustine needs more iron than Bermuda in alkaline soils. If iron deficiency is chronic — yellowing returns each season — the root cause is pH above 7.0 locking out iron. Lime or sulfur correction addresses the cause; iron applications address only the symptom.
If you’ve got St. Augustine grass, you’ll like this 1-gallon liquid from TPS NUTRIENTS. You’ll apply a balanced formula made in the USA that’s tailored for warm-season lawns, promoting thicker turf, stronger stolons, deeper roots and a rich, consistent green. It’s gentle to reduce nutrient burn, so you can use it regularly without stressing your yard. The 128 fl oz liquid targets residential and commercial turf, yards and landscapes, and aims for long-lasting seasonal results while avoiding nutrient buildup. Coverage is listed as low, so plan applications accordingly and follow label directions for best outcomes.
Our Take: Liquid iron bypasses the soil chemistry problem by delivering iron directly to leaf tissue — pH interference doesn’t affect foliar absorption. Results are visible within 48 hours and last 3–4 weeks before the treated leaf tissue grows out.
- Targeted for St. Augustine:Formulated specifically for St. Augustine grass
- Product Form:Liquid
- Primary Use:Lawn food / fertilizer for turf health and color
- Coverage or Unit Size:128 fl oz (1 gallon) — labeled coverage: Low (concentrated)
- Season / Application Timing Guidance:For warm-season lawns; regular program through growing season
- Additional Nutrient / Additives:Balanced nutrition; gentle formula (no specific extra micronutrients listed)
- Additional Feature:Gentle low-burn formula
- Additional Feature:Promotes stolon strength
- Additional Feature:Made in USA
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Scotts Green Max Lawn Food with Iron Supplement
Choose Scotts Green Max Lawn Food with Iron if you want a fast, easy way to feed and deeply green your St. Augustine. This 16.67 lb bag covers 5,000 sq. ft., combining fertilizer and 5% iron for visible greening in about three days. Use a Scotts spreader (broadcast/rotary 3¾ recommended, drop 7½) and lightly water after application. It’s suitable in spring, summer, and fall and works on any grass type. People and pets can re-enter immediately. Follow directions to avoid staining on hard surfaces. Manufactured by The Scotts Company LLC; model 44615A, UPC 032247446150.
- Targeted for St. Augustine:Suitable for any grass type (includes St. Augustine)
- Product Form:Granules
- Primary Use:Lawn food with iron for feeding and greening
- Coverage or Unit Size:16.67 lb bag — covers 5,000 sq ft
- Season / Application Timing Guidance:Recommended spring, summer, fall applications
- Additional Nutrient / Additives:Includes 5% iron supplement (micronutrient) for fast greening
- Additional Feature:Fast deep greening (~3 days)
- Additional Feature:Includes 5% iron
- Additional Feature:Spreader-specific settings
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St. Augustine Liquid Grass Fertilizer – 8 oz
For homeowners and landscapers who want a concentrated, easy-to-use feed specifically for St. Augustine grass, TPS NUTRIENTS’ St Augustine Grass Fertilizer – Liquid Lawn Food (8 oz) delivers targeted nutrition. You’ll apply a concentrated liquid that’s formulated for warm-season turf to promote thicker turf, denser growth, stronger stolons and roots, and a richer green color. Its gentle, balanced formula minimizes nutrient burn and buildup, so you can include it in regular lawn-care programs for consistent, long-lasting results. Made in the USA and suited to residential or commercial lawns, this low-coverage product works well for established St. Augustine turf.
Our Take: A formulation labeled specifically for St. Augustine carries an NPK ratio weighted for the grass’s typical requirements — moderate nitrogen with iron and micronutrient support. The premium over a generic high-N formula is justified when your soil shows signs of micronutrient deficiency.
- Targeted for St. Augustine:Formulated specifically for St. Augustine grass
- Product Form:Liquid
- Primary Use:Lawn food / fertilizer for turf health and color
- Coverage or Unit Size:8 fl oz (small concentrate) — coverage: Low (concentrated)
- Season / Application Timing Guidance:For warm-season lawns; regular program through growing season
- Additional Nutrient / Additives:Balanced nutrition; gentle formula (no specific extra micronutrients listed)
- Additional Feature:Concentrated small bottle
- Additional Feature:Gentle low-burn formula
- Additional Feature:Promotes stolon strength
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Sunniland Weed & Feed for St. Augustine Grass
Homeowners with St. Augustine lawns will find Sunniland St. Augustine Weed & Feed Lawn Fertilizer a straightforward option. You’ll cover 5,000 sq ft per 20‑lb bag of easy‑to‑spread granules formulated for all St. Augustine types. Apply twice yearly—spring and fall—to feed turf and control most broadleaf weeds and dollarweed. The product lists a 1:0:0 mixing ratio, comes in a single bag, and carries model number 128820 (ASIN B0DWHJ2F6R). Manufacturer and brand are generic, and it’s sold in Patio, Lawn & Garden fertilizer categories. User feedback is positive: 37 reviews average 4.6 out of 5.
Our Take: Verify herbicide active ingredients before applying any weed-and-feed to St. Augustine. Atrazine at high rates or in heat stress conditions can cause significant turf damage. Not all weed-and-feed products are St. Augustine-safe.
- Targeted for St. Augustine:Designed for St. Augustine grasses
- Product Form:Granules
- Primary Use:Weed & feed (fertilizer plus weed control)
- Coverage or Unit Size:20 lb bag — covers 5,000 sq ft
- Season / Application Timing Guidance:Two applications recommended: spring and fall
- Additional Nutrient / Additives:Weed-control ingredients included (broadleaf and dollarweed control)
- Additional Feature:Controls broadleaf weeds
- Additional Feature:Two recommended applications
- Additional Feature:5,000 sq ft coverage
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Andersons Professional PGF 16-4-8 Fertilizer (5,000 sq ft)
If you want a high-performance feed that gives an immediate green-up and up to eight weeks of extended nutrition, the Andersons Professional PGF 16-4-8 is a smart pick—its super-fine granules and 7% Humic DG deliver even particle distribution and added soil-conditioning benefits for St. Augustine. You’ll apply an 18-pound bag to cover about 5,000 sq ft, getting a 16-4-8 N-P-K blend with iron and micronutrients. Its mix of quick- and slow-release nitrogen provides instant color and sustained growth. It’s designed for lawn grasses, conditions soil, and isn’t available for sale in California.
- Targeted for St. Augustine:Intended for lawn grasses including St. Augustine
- Product Form:Super-fine granules
- Primary Use:Complete turf fertilizer and soil conditioning
- Coverage or Unit Size:18 lb bag (288 oz) — covers 5,000 sq ft
- Season / Application Timing Guidance:Provides immediate + extended feeding (up to ~8 weeks) — general lawn use periods
- Additional Nutrient / Additives:Includes iron, micronutrients and 7% Humic DG; mix of quick + slow release nutrients
- Additional Feature:16-4-8 N-P-K formula
- Additional Feature:Quick + slow release
- Additional Feature:Contains 7% Humic DG
Factors to Consider When Choosing Fertilizer for St. Augustine Grass
When choosing a fertilizer for your St. Augustine grass, consider your soil type and the grass’s growth stage so you can match nutrients to actual needs. Look at the nutrient ratio and decide whether a slow‑release or quick‑release formula fits your timing and maintenance plan. Also plan applications around season and weather to get the best uptake and avoid runoff.
Soil Type
Because soil texture controls how water and nutrients move, you should match your fertilizer strategy to the type of soil hosting your St. Augustine. If you have sandy loam to loam, use standard formulations and apply at rates assuming moderate nutrient retention and quick percolation. On heavy clay, favor slow‑release nitrogen and add organic matter to prevent nutrient lock‑up and reduce salt stress. For coarse sandy soils with low cation‑exchange capacity, split fertilizers into smaller, more frequent applications and incorporate compost to boost nutrient holding and limit leaching. Always test soil pH first—St. Augustine prefers about 5.0–8.5—and amend with lime or sulfur per recommendations. Use a full soil test to set exact fertilizer types and rates and correct deficiencies.
Grass Growth Stage
Match your fertilizer plan to how your St. Augustine is growing. When grass is in active spring and summer growth, apply higher-nitrogen products to promote stolon expansion and a dense canopy. For newly established turf, use a gentle, balanced feed with lighter, more frequent applications to encourage root and stolon development without burning or forcing excessive top growth. Cut back or stop nitrogen as growth slows in fall and winter; uptake drops during cool stress and dormancy, raising leaching and imbalance risks. Always monitor turf color, vigor, compaction, and recent precipitation, and adjust rate and frequency so you fertilize to growth stage rather than calendar dates. Matching timing to growth maximizes efficiency and turf recovery.
Nutrient Ratio Needs
Picking the right N-P-K balance matters for St. Augustine grass. You’ll typically favor higher nitrogen during the active growing season to drive thick, green leaf and stolon growth. For established lawns, choose formulas with moderate-to-low phosphorus and relatively higher potassium—too much phosphorus can accumulate, while potassium boosts stress and disease tolerance. Use slow-release nitrogen or a blend of quick- and slow-release sources so you get steadier growth, fewer clippings, and less burn risk. Base rates on a soil test and turf condition, targeting common warm-season annual totals (about 2–4 lbs N per 1,000 sq ft) divided into multiple applications. Increase nitrogen in late spring/early summer and reduce it in fall to avoid winter-vulnerable late growth.
Application Timing
When choosing when to fertilize St. Augustine grass, apply during active warm-season growth—usually late spring through summer—when soil temperatures stay above about 65°F so the turf can take up nutrients. Don’t fertilize before green-up in early spring or after growth slows in late fall; timing around dormancy wastes product and risks burn. Space applications of slow‑release or balanced fertilizers about every 6–8 weeks during the growing season to maintain steady nutrition and lower burn risk. Avoid applying just before heavy rain or major irrigation to prevent runoff; water lightly after application only if the fertilizer label recommends it. Get a soil test first to identify nutrient needs and pH, and adjust timing for local climate nuances.
Slow‑Release Versus Quick‑Release
Decide whether you want steady, long-term feeding or a quick color boost, because slow‑release and quick‑release fertilizers behave very differently and suit different needs. Slow‑release nitrogen delivers nutrients gradually over weeks to months, so you’ll get steady root and stolon growth, fewer growth surges, less frequent mowing, and reduced leaching during hot, rainy periods. Quick‑release gives an immediate spike—useful when you need fast greening or corrective feeding—but it drives rapid top growth, increases mowing, and raises scorch and burn risk in high temperatures. You can also choose a blend: quick‑release for initial color and slow‑release for sustained nutrition, balancing short‑term appearance with longer‑term turf health. Apply quick‑release cautiously in heat.
Iron And Micronutrients
Recognizing that St. Augustine grass often benefits from iron applications because iron promotes deep greening and chlorophyll production without stimulating excessive top growth like high-nitrogen fertilizers. You should test soil or tissue before routine micronutrient programs since pH and organic matter affect availability; alkaline soils commonly cause iron and manganese deficiencies. Apply iron as a chelated form or sulfate at recommended rates (typically 0.5–2 lb Fe per acre for sulfate or label rates for chelates) to avoid foliar burn and staining. Remember micronutrients—manganese, zinc, copper—are needed in small amounts for enzyme function and stress tolerance; deficiencies show as interveinal chlorosis or stunting. Use micronutrients only as supplements to a balanced N-P-K plan and avoid overapplication, which can create antagonisms and harm turf.
Application Method
Although the nutrient form matters, you should pick an application method that matches your schedule, equipment, and turf goals. Liquid fertilizers give faster uptake and quicker greening, so use them when you want rapid response; dilute and apply with a hose‑end or backpack sprayer at the labeled rate, and water in lightly to move nutrients into the root zone. Granular slow‑release products feed longer and cut applications—apply them with a calibrated broadcast or drop spreader using manufacturer settings to avoid streaks or burn. Time all applications for active growth (spring through early fall) and avoid dormancy or extreme heat. Measure your lawn area and calibrate equipment so you apply the correct rate per 1,000 sq ft and prevent over‑application.
Environmental Safety
You’ve picked an application method that fits your schedule and equipment, but you also need to consider environmental safety when choosing a fertilizer for St. Augustine grass. Choose balanced N-P-K formulas with controlled-release nitrogen to cut leaching and runoff that fuel eutrophication. Don’t overapply—measure your lawn and follow label rates to avoid groundwater contamination and algal blooms. Prefer products with a low salt index and mild soluble salts to reduce root burn and soil salinization that stress turf and nearby plants. Time applications for active growth and avoid fertilizing before heavy rain to minimize surface runoff. Test soil every two to three years for pH and nutrient levels so you only add what’s necessary, preventing unnecessary environmental loading.
Expert Selection Notes from 6BC
If St. Augustine shows chronic iron chlorosis (yellow leaves, green veins), test soil pH before buying more iron. pH above 7.0 locks out iron regardless of application rate. Lower pH with sulfur as the long-term fix; use liquid chelated iron for immediate cosmetic correction while the pH program takes effect.
For liquid iron products specifically formulated to correct chlorosis across all grass types, see our liquid iron guide. Full framework: lawn care guide.