In the summer heat, proper care for St. Augustine grass is vital to maintain a vibrant, healthy lawn. Essential practices include mowing at the ideal height for St. Augustine, watering efficiently to prevent excessive moisture and choosing fertilizers that bolster St. Augustine during stressful conditions. Equally important are effective weed and pest control strategies and disease prevention tailored to St. Augustine's specific needs. This guide delivers expert advice for nurturing St. Augustine grass, ensuring it flourishes throughout the summer months.
Be sure to also check out our series of Homeowner Maintenance Guides for generic St. Augustine, Palmetto® St. Augustine and CitraBlue® St. Augustine.
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1. Keep Up with Summer Mowing (and Reduce the Time Spent on This Chore)
Summer mowing can be challenging due to the heat and the need for frequent cuts to manage grass growth. For St. Augustine grass, ideal mowing heights are 2–4 inches, with shaded areas needing 3–4 inches. Recommended heights for specific varieties are:
- Palmetto: 2–2.5 inches
- CitraBlue: 2–3 inches
- Floratam: 3–4 inches
Always trim no more than a third of the grass blade to prevent stress and browning. If you go on a vacation or break and your grass gets too tall while you’re gone, mow gradually to the desired height, allowing 3–5 days between mowings. Taller blades benefit the lawn by shading the root system and retaining moisture.
Note: Get ahead of summer mowing and check out our tips on reducing time spent mowing your lawn as it gets hotter outside: How to Mow Your Lawn Less During the Summer.
2. Keep Your Heat-Stressed St. Augustine Strong with the Right Summer Fertilizer
St. Augustine grass needs tailored nutrients as seasons change, especially to combat summer heat stress. It requires less nitrogen in summer to avoid scorching under intense heat and sunlight.
Sod University suggests two summer fertilizer options, but recommends using only one:
- Lawnifi® Summer Fertilizer Box: A liquid fertilizer set designed for St. Augustine lawns, including one bottle of Maintain (16-0-4) for potassium, amino acids, and carbon, and two bottles of Recover (13-0-0) for an optimal nutrient balance plus essential micronutrients. It attaches easily to a garden hose for application.
- Lawnifi Foundation: A 25-pound bag of granular fertilizer with a 29-0-5 NPK ratio, providing slow-release nitrogen and 2 percent iron for a prolonged, healthy lawn growth without nitrogen overload.
Both products cover 5,000 sq. ft.
3. Make Sure Your St. Augustine is Hydrated...But Not Too Hydrated
Despite the temptation to water more in summer, St. Augustine grasses typically need only 1 inch of water weekly, including rainfall, to avoid disease-promoting waterlogged conditions. Aim for one or two deep waterings early in the morning each week to minimize dew duration and reduce disease risk and take rainfall into consideration.
Watering in the early morning decreases the amount of time dew is present, which is helpful for managing any potential disease outbreaks. Unsure of measuring water? Try an irrigation audit. If heat stress appears, top dressing may help cool and protect your lawn.
4. Be Cautious with Weed Control
Applying weed control to St. Augustine grass in summer can harm it, especially when temperatures exceed 85°F. It's safer to apply post-emergent herbicides when it's cooler and use pre-emergent herbicides in spring and fall to manage seasonal weeds.
If below 85°F, you can cautiously apply post-emergent herbicides, but it's advised to wait for cooler fall conditions to avoid risk, as subsequent hot days can still cause damage.
For more details, see How to Control Weeds During the Summer. Common summer weeds include dollarweed, knotweed, spurge, lespedeza, crabgrass, goosegrass, nutsedge and sandspur.
Pictured above: Dollarweed.
Be sure to read herbicide labels thoroughly before application.
5. Watch Out for Insect Infestations or Damage
Summer brings insect challenges to lawns, including fire ants, mosquitoes, chinch bugs, grub worms, mole crickets, fall armyworms, and sod webworms, all capable of causing significant damage.
Pictured above: A sod webworm.
To identify grub worm issues, look for increased activity from burrowing animals like moles or inspect the soil directly. Preventative insecticide applications against grubs, particularly from beetles like the Japanese and May/June beetles, are recommended around June, using products like Acelepryn.
Chinch bugs, problematic in St. Augustine grass, manifest as patchy, drought-like damage. Dylox 6.2 is effective against them. Sod webworms and fall armyworms chew on grass blades, leaving a transparent, "windowpane" appearance, with the latter distinguishable by a green or brown color and a black stripe.
Mole cricket damage is visible through their soil-uplifting tunnels and the brown, dying grass they leave behind.
Before using any insect control products, thoroughly read the label. For more on lawn insects, see Insect Identification. Be sure to read labels thoroughly before application.
6. Relax About Disease Control
Disease outbreaks in St. Augustine lawns are rare but can occur with summer overwatering, with gray leaf spot being the most common due to warm, wet conditions.
Pictured above: Grey leaf spot in St. Augustine grass.
Preventative cultural practices from the St. Augustine Homeowner Maintenance Guide can help avoid diseases. These practices promote a resilient, healthy lawn.
For disease control, consider the recommended products below, ensuring to read their labels carefully. For more information on lawn diseases, refer to Identifying Common Lawn Diseases. Be sure to read labels thoroughly before application.
Summer lawn care tips for your St. Augustine lawn are mostly about keeping it healthy and stress-free during the hot summer temperatures. This will help it continue to thrive when temperatures eventually cool down and we enter into the fall season. We will see you back here in the fall for our updated fall maintenance tips for St. Augustine.
And remember…if you want lawn care made simple, the Lawnifi Complete Subscription provides your lawn with what it needs during the current season and for years to come.
