Specs are compiled from manufacturer listings and verified buyer reviews and can change over time — please confirm the key details on the product page before buying.
Fall feeding sets up your St. Augustine lawn for a strong spring green-up, but the wrong fertilizer can do more harm than good. St. Augustine grass needs a specific blend of nutrients heading into cooler months — enough potassium for root hardiness, slow-release nitrogen so you don’t force tender growth before a freeze, and zero weed-killers that might damage this sensitive southern turf. You want a formula that strengthens root systems and helps the lawn store energy, not one that pushes top growth that winter will kill back.
I’m Rikta — the founder and writer behind Lawn Gear Lab. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
Below are the best fall fertilizers for St. Augustine grass, chosen for their NPK ratios, coverage area, and proven results during the autumn window. This is your complete guide to picking the right fall st augustine grass fertilizer for a healthier lawn next year.
Our Picks at a Glance
How To Choose The Best Fall St Augustine Grass Fertilizer
Fall feeding is about setting roots for winter, not pushing blade growth. A good fall fertilizer for St. Augustine is high in potassium (the third number in the NPK ratio) and uses slow-release nitrogen. The right product helps the lawn store carbohydrates, strengthens cell walls against cold, and leads to earlier spring green-up.
NPK Ratio and Your Fall Goals
You want a fertilizer with a higher third number (potassium, or K) and a moderate first number (nitrogen, or N). A ratio like 15-0-15 or 30-0-12 is ideal for fall. The middle number (phosphorus) can be zero on most southern lawns — soil tests usually show adequate phosphorus levels, and adding it can run off into waterways. The potassium helps the grass regulate water and resist temperature stress.
Slow-Release vs. Quick-Release Nitrogen
Slow-release nitrogen feeds the lawn steadily over weeks, reducing the risk of a growth surge that winter will damage. Quick-release nitrogen forces a fast green-up that demands frequent mowing right when the grass should be slowing down. Look for terms like “slow-release nitrogen,” “poly-coated,” or “SCU” (sulfur-coated urea) on the label to protect your St. Augustine heading into dormancy.
Quick Comparison
| Model | Best For | NPK Ratio | Coverage | Bag Weight | Amazon |
|---|---|---|---|---|---|
| Scotts WinterGuard Fall Lawn Food★ Best Overall | Overall fall feeding | 32-0-10 | 12,000 sq. ft. | 32.3 lbs. | Amazon |
| Simple Lawn Solutions 0-0-25Best Value | Potassium boost | 0-0-25 | 3,200 sq. ft. | 2 lbs. | Amazon |
| Fertilome Centipede 15-0-15Top Performer for Repairs | Repair with plugs | 15-0-15 | 5,000 sq. ft. | 16 lbs. | Amazon |
| Almighty 20-0-10 | Fast greening + root strength | 20-0-10 | — | 18 lbs. | Amazon |
| TPS St. Augustine Grass Fertilizer | Quick liquid feeding | — | Low | 1 gal. | Amazon |
| Fertilome St. Augustine Weed & Feed | Fertilizer + weed control | 15-0-4 | 5,000 sq. ft. | 25.6 lbs. | Amazon |
| GreenView Fairway Formula Fall | Premium slow-release feeding | 30-0-12 | 15,000 sq. ft. | 45 lbs. | Amazon |
| SeedRanch St. Augustine 24-2-11 | High-iron greening | 24-2-11 | 12,000 sq. ft. | 50 lbs. | Amazon |
| LESCO 17-0-17 Weed & Feed | Large-area pro treatment | 17-0-17 | ~13,000 sq. ft. | 50 lbs. | Amazon |
In‑Depth Reviews
1. Scotts Turf Builder WinterGuard Fall Lawn Food
Our pick — over 4.5★ from 13,500+ verified ratings; the strongest balance of quality and price.
The million-bag fall classic that keeps St. Augustine green even in a deep freeze.
Scotts WinterGuard is the most trusted fall fertilizer for a reason — the 32-0-10 NPK ratio delivers a big dose of nitrogen and a strong potassium kick in a single 32.3-pound bag that covers 12,000 square feet. That high third number (10% potassium) is exactly what St. Augustine needs heading into winter: it strengthens root cell walls against cold and drought. The 32% nitrogen is mostly slow-release, so you avoid the tender surge that a quick-release product would cause going into November.
Owner experiences back up the label. Buyers report putting this down in late fall and seeing grass stay “bright green” even when temperatures dropped to 25°F. One owner specified that the grass stayed green “not growing wild” through winter — exactly the kind of controlled dormancy you want from a fall feed. The bag covers any grass type, including St. Augustine, so there is no worry about species compatibility.
The crowd favorite — 4.6 stars from over 13,000 ratings — confirms this is a low-risk, high-reward pick for anyone who wants one reliable bag for the whole fall season. It builds roots through the cold months so spring green-up starts stronger.
Winter prep booster
- Massive 12,000 sq. ft. coverage from one bag saves trips to the store
- High 32-0-10 ratio feeds roots without pushing risky winter growth
- Proven to keep St. Augustine green through sub-freezing temps
Not for warm season
- If your lawn needs a targeted potassium boost without nitrogen, a 0-0-25 product may suit better
Fall feeding: you want a single, proven fall fertilizer that feeds roots across a large St. Augustine lawn and keeps green color through winter dormancy.
Warm climates: your soil test shows nitrogen is already high and you only need to supplement potassium.
2. Simple Lawn Solutions High Potassium Lawn Food 0-0-25
A pure potassium punch for St. Augustine lawns that need winter hardiness, not more nitrogen.
If your soil test shows nitrogen is already adequate but your St. Augustine looks stressed by heat or traffic, this liquid 0-0-25 fertilizer delivers exactly what the grass needs: a straight 25% potassium dose with zero nitrogen or phosphorus. Potassium promotes turf grass hardiness, helping the lawn prepare for temperature changes and stressful winter conditions. The 32-ounce bottle comes with a ready-to-use hose-end sprayer that covers up to 3,200 square feet at the perfect dilution ratio.
The effectiveness is what owners praise most — 38 positive mentions in the review data. One owner noted that application is straightforward, and while they “didn’t see a lot of difference in the yard overall,” they were sure it “has helped aid the grass root system.” Another owner was happy they could use this with a backpack sprayer for more precise coverage. At just 2 pounds total weight, it is dramatically lighter than granular alternatives — the Fertilome centipede fertilizer weighs 8x more at 16 pounds.
The main honest tradeoff: because this has no nitrogen, you will not see the fast green-up that a blended product provides. It is a targeted tool for root strength and winter survival, not a cosmetic greener. It also earned 4.5 stars across 600+ ratings, so most owners found it does its job.
Potassium fix: your fall plan is to boost potassium specifically — for stronger roots and cold hardiness — without adding more nitrogen to the lawn.
General feeding: you want a traditional fall fertilizer that also greens up the lawn; you will need a blend with nitrogen for that effect.
3. Fertilome Centipede Lawn Fertilizer 15-0-15
The balanced 15-0-15 formula that saves new plugs and turns St. Augustine a deep green.
Fertilome’s 15-0-15 blend is a smart choice for fall repair work — specifically, laying new St. Augustine plugs in damaged spots. The 15% slow-release nitrogen feeds steadily without the burn risk that tender new grass cannot handle, and the 15% potassium supports root development through winter. The bag covers up to 5,000 square feet at the recommended 4 pounds per 1,000 square feet, and the added iron prevents and corrects yellow foliage so your lawn gets that “fast super green” look owners describe.
Buyers who used this with new plugs for damage spots report that they “did not lose any of the plugs” and saw a “much deeper green color.” The germination aspect is the single most praised feature — 10 owners cite it directly. Another owner simply said their lawn became “thick as biscuit batter.” The product works on St. Augustine, centipede, Bermuda, Zoysia, and other warm-season grasses, so it is flexible across southern lawns.
The 16-pound bag is a mid-weight option — lighter than the 50-pound SeedRanch bag but heavier than liquid concentrates. That makes it easy to handle for a 5,000-square-foot application. It earned 4.7 stars from 100+ ratings, making it the highest-scoring product in this lineup behind the GreenView premium bag.
Centipede lawns: you are repairing bare spots with plugs or sod in the fall and need a gentle, iron-rich fertilizer that supports new root establishment without burning.
Other grasses: your lawn is large (over 5,000 sq. ft.) and you would rather buy one larger bag than multiple smaller ones.
4. Almighty 20-0-10 Lawn Fertilizer
Professional-grade granules that green up St. Augustine within days and feed for up to 8 weeks.
Almighty’s 20-0-10 formula uses slow-release nitrogen that produces visible greening within days and continues feeding for up to 8 weeks — no surge growth or burn risk when applied correctly. That is precisely the timeline you want for a September or early October application, because it carries the lawn through late fall without forcing growth into first frost. The added NuTrace micronutrients support chlorophyll production and disease resistance, which is useful for St. Augustine lawns coming out of a stressful summer.
Owners of St. Augustine grass specifically confirm the results. One noted that their “St Augustine looks great after applying this.” Another owner with tall fescue saw green grass within two weeks, though they noted the product did not kill white clover (it is not a weed killer). The 18-pound bag is designed for broadcast spreaders, and at 4–5 pounds per 1,000 square feet, it covers a medium-sized yard efficiently.
One honest nuance: the label specifies spring/summer for Bermuda and Zoysia but reads “Tall Fescue, Kentucky Bluegrass – Apply Fall & Winter.” For St. Augustine, early fall is fine — just avoid applying past October in regions where hard freezes arrive early. The product earned 4.6 stars from 75 ratings, and every single recorded review is 5-star, which says something about consistency.
Even growth: you want fast, sustained greening in early fall with professional-grade micronutrients and zero phosphorus.
Weed issues: you need a dedicated weed-and-feed product, since this fertilizer does not include any herbicide.
5. TPS Nutrients St. Augustine Grass Fertilizer
A quick-absorbing liquid designed specifically for St. Augustine — no guesswork on NPK ratios.
TPS Nutrients made a liquid fertilizer specifically for St. Augustine grass, so you know the formulation targets that grass type’s unique needs. The fast-absorbing liquid formula delivers nutrients efficiently for visible improvements in growth, color, and turf health. It supports deep root systems for better durability in warm climates and heavy use — exactly what a St. Augustine lawn needs going into fall after a hot southern summer. The 1-gallon bottle is a concentrate, so you dilute and apply with a hose-end sprayer or watering can.
Owners mention seeing results quickly. One says it greens up in about 4–5 days “especially st Augustine.” Another owner described it as a “simple to use way to fertilize finicky St. Augustine,” diluting it to use twice as often with less watering required. A third owner saw green color return “after two applications” on their St. Augustine lawn.
The tradeoff: liquid fertilizers typically cost more per square foot than granular, and the 1-gallon bottle has a “Low” coverage rating in the specs, so it is best for small lawns, spot treatments, or supplementing a granular program. The rating is 4.2 stars from 89 ratings — solid but the lowest among top picks here, mainly because a few owners wanted faster greening than the first application delivered.
St. Augustine: you have a smaller St. Augustine lawn or want a liquid supplement for spot areas and need fast absorption without granular spreader setup.
Bermuda lawns: you have a large lawn (over 5,000 sq. ft.) where granular coverage is more cost-effective per application.
6. Fertilome St. Augustine Weed & Feed 15-0-4
A targeted 15-0-4 weed-and-feed with Atrazine that is safe for St. Augustine but not for Bermuda.
Fertilome’s St. Augustine Weed & Feed combines a 15-0-4 fertilizer with Atrazine, a pre-emergent and post-emergent herbicide that controls weeds while feeding the lawn. This is specifically formulated for St. Augustine, Centipede, and Zoysia — and the label explicitly warns against use on Bermuda grasses or northern grass types. The 25.6-pound bag covers 5,000 square feet, and the Atrazine stops broadleaf weeds from germinating while also killing existing ones.
Seasoned St. Augustine owners swear by this product. One who used it for years says “applied at the proper time of year it will fertilize the lawn and kill the weeds.” Another owner in Florida reported it made their St. Augustine “thrive, thicken up and green up from the Florida rain.” A third noted it was effective on a drought-damaged lawn with brown patches, applied with a Scotts spreader at the recommended setting. The 4.3-star rating from 74 reviews is solid, and the few lower ratings mostly reflect timing mistakes — applying too late or early relative to the weed cycle.
The biggest caution: do not use this on Bermuda or northern grasses. If your lawn is mixed St. Augustine and Bermuda, skip this product and use a straight fertilizer instead. Also, fall is primarily for fertilizing, not weed control, so time the application for when weeds are actively growing — typically early fall.
Weed control: your St. Augustine lawn has visible winter weeds and you want a single product that feeds and controls them in the fall window.
Hot weather: your lawn contains Bermuda grass or you prefer to spot-treat weeds separately from your fall fertilizer program.
7. GreenView Fairway Formula Fall Lawn Fertilizer 30-0-12
The nearly 60% slow-release nitrogen formula that keeps St. Augustine green all winter without surge growth.
GreenView Fairway Formula is the premium fall option for a reason — the 30-0-12 NPK ratio contains nearly 60% slow-release nitrogen and zero phosphate, which means steady feeding that does not push risky winter growth. The 45-pound bag covers an enormous 15,000 square feet, so it is the best value per square foot for large lawns. The potassium (12%) is the highest in this lineup after the dedicated potassium product, giving St. Augustine roots the winter hardiness they need. The result, as owners describe, is a “deep kelly green lawn that stayed green through winter into late spring.”
The quality aspect is the most-talked-about feature — 23 owners cite it. Owners specifically praise the moisture-proof packaging, which prevents the clumping that plagues many granular fertilizers. One long-time buyer noted they “used for three consecutive falls” and saw noticeable improvement in lawn health, calling it worth the slightly higher cost.
The one honest caveat: this is a premium-priced product in the lineup. Some owners find it “a bit pricey” though most agree it is “well worth the money.” The rating is 4.7 stars from 428 ratings — tied for the highest score here and a strong signal of consistency.
Fall recovery: you have a large St. Augustine lawn (over 10,000 sq. ft.) and want premium slow-release feeding with the best winter color retention on the market.
Spring use: you have a small lawn and do not want to store a 45-pound bag for next season.
8. SeedRanch St. Augustine Lawn 24-2-11 Fertilizer
The Lesco-formulated 24-2-11 blend with 6% iron that produces deep greening without excessive growth.
SeedRanch’s St. Augustine-specific fertilizer uses a Lesco formulation with 24-2-11 NPK and a notable 6% iron content. That high iron level is the key feature for fall because it promotes dark green color through chlorophyll production without forcing leaf growth — exactly what you want as the grass heads into shorter days. The 50-pound bag covers 12,000 square feet, making it comparable to the Scotts WinterGuard in coverage but with a lower nitrogen percentage and added iron.
Customers note rapid results on St. Augustine. One buyer applied before heavy rain in California and reported their “St. Augustine grass grew rapidly with dark green color.” Another neighbor-envy story: “My neighbor’s envy my yard.” The Lesco heritage gives it professional credibility — Lesco is a well-known brand in the turf management industry. The 4.5-star rating from 106 reviews is consistent and positive, though a few owners noted it takes time for the full effect to show up.
An honest note: the bag is 50 pounds, which is heavy to handle and store. It also contains a small amount of phosphorus (2%), which is fine for most soils but note if you live in an area with phosphorus restrictions. The 6% iron can stain concrete if you spill the granules and leave them wet, so sweep up any overspray on driveways or sidewalks.
Color boost: your St. Augustine lawn looks pale or yellowish and you need an iron boost along with fall nutrition — the 6% iron is the highest in this list.
Low nitrogen: you have a phosphorus restriction in your area or you prefer a bag under 50 pounds for easier handling.
9. LESCO St. Augustine Grass Weed and Feed 17-0-17
A professional 17-0-17 weed-and-feed with Penoxsulam that covers a massive area for the price.
LESCO’s 17-0-17 St. Augustine Turf Fertilizer combines an even nitrogen-potassium ratio with Penoxsulam herbicide, a post-emergent that targets broadleaf weeds while being safe for St. Augustine (including the Floratam variety). The 50-pound bag covers between 12,000 and 14,000 square feet, which is the largest coverage range in this guide. The formula uses 30% poly-coated sulfur-coated urea for slow-release feeding that lasts up to 8 weeks — meaning one fall application can carry the lawn through to dormancy.
Owner responses are mixed compared to other picks here. Some see excellent results: “Not only kills weeds but improves insect infestation too.” Others are disappointed, with one calling it a “waste of money” after seeing no results. The 3.9-star rating from 69 reviews is the lowest in this lineup, and that mixed feedback likely reflects the challenge of timing a weed-and-feed product correctly. The herbicide needs to be applied when weeds are actively growing and the grass is not stressed, which is a narrower window than straight fertilizer.
The key to success with this product: apply it when the turf is wet, allow it to dry on the blades, and expect visible results in about 2 weeks. It is safe for the Floratam variety of St. Augustine, which is a common southern lawn type. If you have a very large lawn (over 12,000 sq. ft.) and want one bag that does double duty, this is a cost-effective choice — but if you have a smaller area and want more predictable results, one of the straight fertilizers above would be a safer bet.
St. Augustine: you have a large St. Augustine lawn with weed pressure and want the biggest bag for your budget with professional-grade slow-release technology.
Centipede lawns: precise results matter more than covering a huge area — the straight fertilizers in this guide have more consistent owner feedback.
Understanding the Specs
NPK Ratio
Those three numbers on the bag stand for Nitrogen (N), Phosphorus (P), and Potassium (K) — in that order. For fall feeding on St. Augustine, you want a higher third number (potassium, the K in NPK) because that is the nutrient that strengthens cell walls and roots for winter survival. The first number (N) should be moderate and slow-release so you do not force green growth that frost will kill. The middle number (P) can often be zero on established southern lawns.
Slow-Release vs Quick-Release Nitrogen
A fertilizer bag will say “slow-release nitrogen” on the label if a portion of its nitrogen is coated (poly-coated or sulfur-coated urea) so it breaks down gradually over weeks rather than all at once. For fall, slow-release is safer because it feeds steadily without a green surge. Quick-release nitrogen gives you fast greening in spring, but in the fall it can push tender growth that gets damaged by first frost and weakens the lawn before winter.
Coverage Area (Square Footage)
The coverage number tells you how much lawn one bag will treat at the recommended rate. A bag labeled for 5,000 square feet is right for a quarter-acre lot, while a bag covering 15,000 square feet suits a full acre. Buy a bag that matches your lawn size — too small and you run out mid-application, too large and you have to store a heavy half-empty bag through winter.
Weed & Feed vs Straight Fertilizer
A weed-and-feed combines fertilizer with a herbicide (like Atrazine or Penoxsulam) to kill existing weeds while feeding the lawn. This saves a pass across the yard, but it only works if applied when weeds are actively growing. Straight fertilizer gives you more control over timing — you can feed in early fall and spot-treat weeds separately. Some herbicides in weed-and-feed products can damage St. Augustine if applied during heat or drought stress.
FAQ
When should I apply fall fertilizer to St. Augustine grass?
Can I use a regular lawn fertilizer on St. Augustine grass?
What NPK ratio is best for St. Augustine in the fall?
Should I use a weed-and-feed on St. Augustine in the fall?
How much fall fertilizer do I need per 1,000 square feet?
Can I fertilize St. Augustine in November?
What happens if I use too much nitrogen on St. Augustine in the fall?
Should I water in fall fertilizer after applying it?
Is liquid or granular fertilizer better for St. Augustine in the fall?
Can I use a centipede grass fertilizer on St. Augustine grass?
Final Thoughts: The Verdict
If you want one dependable pick, the fall st augustine grass fertilizer winner is the Scotts Turf Builder WinterGuard Fall Lawn Food because it has the most proven track record for fall root feeding, with a 32-0-10 ratio that delivers high potassium and slow-release nitrogen in a single bag that covers 12,000 square feet. If you want pure potassium for root hardiness without extra nitrogen, grab the Simple Lawn Solutions 0-0-25. And for premium slow-release performance across a large lawn with winter-long green color, the GreenView Fairway Formula 30-0-12 is the one to reach for.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of July 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
As an Amazon Associate, Lawn Gear Lab earns from qualifying purchases. This does not affect which products we feature.