7 Best Summer Fertilizer For St Augustine Grass | Dark Green

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A 7-in-1 liquid that turns your lawn dark green in under a week without the surge of growth that needs constant mowing.

The big number on this one is the volume: 64 fluid ounces, giving you 8,000 square feet of coverage per bottle. The PetraMax bottle contains 64 fluid ounces, compared to 32 fluid ounces for the Advanced 16-4-8 and the Maximum Green 28-0-0. The NPK analysis sits at 19-0-0, with 2.5% iron and humic acid blended in — that iron is what drives the deep color buyers rave about without relying purely on nitrogen to do it.

Buyers report that grass became thicker and darker green within 1-3 days of applying Neighbor’s Envy, and one reviewer noted their lawn was the thickest and darkest it had ever been by early June after combining it with overseeding. The formula also includes sea kelp and sulfur, which support root strength and drought resistance — useful for St. Augustine in peak summer heat. On the flip side, a few buyers found the price per bottle high for very large lawns, and noted that the fast green-up comes partly from staining, not just true greening, so reapplication every 2-4 weeks is needed for continued effect.

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The overnight green-up champion with a built-in sprayer — buyers saw results by the next afternoon.

This liquid comes ready to use with an attached sprayer that covers up to 3,200 square feet, and the mixing is zero: you hook it to the hose and spray. The NPK ratio is 28-0-0, with 70% of the nitrogen being quick-release for immediate uptake and 30% slow-release to keep feeding between applications. That rapid nitrogen hit is what produces the dramatic color change buyers describe.

One Florida buyer sprayed it around 5 PM and “by the next afternoon my entire front yard was already a very deep and beautiful green,” noting that a dead strip along the driveway sprouted new grass within days. Another reviewer mentioned it is pet-safe — you can let dogs back on the lawn right away — which matters for summer evenings. The attached sprayer makes it the easiest option to apply, but the 32-ounce bottle is small compared to the 64-ounce PetraMax, so if you have a larger lawn you will either need multiple bottles or a different solution. A minority of buyers said it did not make a difference, so results vary with soil condition.

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A gallon-sized liquid that is built specifically for St. Augustine, with a slower approach that keeps you cutting less.

This one stands out for its pure focus: it is labeled directly for St. Augustine grass, not just “all grass types.” The liquid volume is 128 fluid ounces — a full gallon, which is the biggest bottle in this list by liquid volume. That makes it a solid choice if you have a medium to large lawn and want a single bottle that will last several applications. It is designed to build strong roots for heat and wear resistance, which is exactly what St. Augustine needs in summer.

One buyer called it a “simple to use way to fertilize finicky St. Augustine,” noting that they water it down and use it twice as often to avoid over-watering, and that it produces a dark green color “just a little slower” — so less cutting and watering. Another reviewer said it greens up in about 4-5 days, especially on St. Augustine. The drawback is that the NPK ratio is not listed in the product specs, so you do not know the exact nutrient breakdown. A couple of buyers found it did not change a tough lawn situation, suggesting it works best when the lawn is not already severely stressed.

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A granular formula with double the potassium of nitrogen, built to protect St. Augustine from summer heat and disease.

This is the only pick here with a potassium-dominant NPK ratio: 10-0-20, plus iron and Nutrace micronutrients for deep green color. The idea is that potassium strengthens the cell walls and roots, making the grass more resistant to drought, disease, and wear — exactly what St. Augustine faces in summer. It covers up to 4,500 square feet from an 18-pound bag, and 45% of the nitrogen is slow-release, feeding steadily for up to 8 weeks without a growth surge.

Reviewers point out the lawn turned a deep green within a week, and one buyer mentioned they would definitely purchase again. The lack of phosphorus (the zero in the middle) is intentional — it is for lawns that already have enough phosphorus in the soil, so a soil test is a good idea before using this. The 18-pound bag is heavier than the liquid options, and you need a spreader to apply it, but the benefit is one application that lasts nearly two months, which is less work in the long run.

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An organic granular with iron and Bio-tone, designed to turn a yellow summer lawn green without harsh chemicals.

This is the only organic option in the lineup, made by the Espoma Company — a brand that has been in the natural organics space since 1929. The 30-pound bag covers up to 5,000 square feet, with an NPK of 8-0-0 that includes iron and their exclusive Bio-tone formula. It is approved for organic gardening and contains no sludges or toxic ingredients. The manufacturer says it will not burn lawns or leach out of the soil, which is a meaningful claim for summer heat when chemicals can scorch grass.

One reviewer who switched from chemical fertilizers said the Espoma Summer Revitalizer showed immediate improvement, and the real benefits increased the longer it was on, even through extreme temperatures. Another buyer noted the granules are “very large pieces,” so you need to adjust your spreader settings — the bag suggestions tend to be a bit light, according to that same reviewer. While the 8-0-0 ratio is lower in nitrogen than synthetic options, the trade-off is safety in heat and a slower, more natural greening process that builds soil health over time. Some buyers felt the price was high, but they also said it was worth it for the confidence and the lack of chemical runoff.

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A heavy-duty 50-pound granular with 6% iron, covering 12,000 square feet and turning neighbors green with envy.

This is the largest bag by weight in the list and the one with the highest coverage: 12,000 square feet from a 50-pound bag of granules. The NPK ratio is 24-2-11, which means high nitrogen for growth, low phosphorus (good if your soil already has it), and meaningful potassium for stress resistance. The standout spec here is the 6% iron content — the highest iron percentage of any pick in this guide — which is specifically listed for “excellent greening.”

Buyers consistently say it produces vigorous growth and a dark green color. One reviewer wrote, “My night is much greater with this fertilizer since I have St. Augustine grass. My neighbor’s envy my yard,” which echoes the sentiment of the PetraMax name. Another said the grass grew “vigorously with dark green color” after applying before heavy rain. The downside is the weight: a 50-pound bag takes some muscle to carry and load into a spreader, and you are committing to a large quantity. If you have a small lawn, you will have a lot left over. But for a large St. Augustine lawn, it is the most cost-effective per square foot.