When to Weed and Feed St. Augustine Grass for the Best Results

As a seasoned gardener, I’m often asked when is the best time to apply weed and feed fertilizer to St. Augustine lawns. Properly timing your weed and feed applications is crucial for maximizing weed control and lawn health. Doing it wrong can damage your grass or render the products ineffective.

Over many years of caring for St. Augustine turf, I’ve dialed in the ideal windows for spring and fall weed and feed treatments. The right timing takes some finesse based on factors like temperature, growth stages, moisture, and more.

In this article, I’ll share my proven tips for perfectly timing your weed and feed applications around peak growth periods. You’ll learn when to target tough weeds like crabgrass and dandelions while invigorating your St. Augustine without risk of burn. Proper watering techniques and safety precautions will also be covered.

If you want your neighbors envying your pristine, verdant lawn free of weeds, you’ll need to master the intricacies of weed and feed timing. Let’s dive in and explore the best practices I’ve discovered through trial, error, and extensive experience caring for St. Augustine grass. Healthy turf starts with properly timed inputs.

What Factors Determine the Best Time to Weed and Feed?

Properly timing your St. Augustine weed and feed applications is crucial for maximizing efficacy and lawn health. Based on my experience, there are several key factors that dictate the ideal window.

Temperature and Growth Stage

The most important consideration is temperature and where your grass is in its growth cycle. Weed and feed products require warm conditions to activate and be absorbed effectively.

Ideally, daytime highs should be consistently reaching 60-85°F before applying. Cool spring or fall temperatures will limit efficacy. Wait until sustained spring green-up or remain active in autumn.

Target feed and weed treatments for peak growing periods. For St. Augustine, this is summer and periods of rapid lateral growth driven by heat and rainfall. Weed and feed too early or late in dormancy won’t nourish the lawn.

Weather and Moisture

Avoid applying weed and feed products during or immediately before extreme heat, drought stress, or heavy rains. High temperatures increase the risk of burning or damaging the grass.

Dry conditions won’t allow the lawn to properly absorb and utilize the nutrients either. Wait until some rainfall or irrigation has moistened the soil before treatment.

Conversely, don’t apply right before an expected major downpour. Heavy rains can wash away granules before they are absorbed. Wait until soakings have leveled off.

Herbicide Tolerances

Weeding and Feeding St. Augustine Grass

Consider weed development stages and turfgrass herbicide tolerances when choosing application dates. Weeds should be young and actively growing for maximum contact and absorption of the weed killers.

Applying too early may miss the prime emergence of key weeds like crabgrass. Go too late, and maturing weeds will be harder to control. Time applications for ideal effectiveness against target weeds.

Certain lawn varieties also handle weed killers better at different points in growth. Know your turf’s stages to avoid overstressing the grass while maximizing weed impact.

Properly timed weed and feed keeps St. Augustine looking its best. Pay close attention to these key factors for success.

Spring Weed and Feed Timing Tips

The ideal window for spring weed and feed application in St. Augustine lawns depends on several factors. Based on years of spring care for my own St. Augustine, here are my top spring timing tips.

Fertilize 4-6 Weeks After Green-Up

In spring, wait until your St. Augustine has fully greened up and initiated active growth before weed and feeding. Rushing too early when soil temps are still cool won’t allow proper nutrient uptake.

I usually apply spring feed and weed around 4-6 weeks after my lawn initially greens up. This ensures the soil has warmed to at least 65°F for activation of the fertilizer and herbicides. The grass is also actively growing to utilize the nutrients.

The fertilizer surge provides energy for rapid spring growth. Weed control is also enhanced once the soil has warmed and weeds are young.

Target Young Crabgrass and Broadleaf Weeds

Spring weed and feed applications are most effective for controlling early crabgrass and broadleaf weeds before they mature. Targeting them while small maximizes results.

For crabgrass, I use a pre-emergent in the early spring window to prevent germination. Broadleaf weeds are best spotted sprayed when young. Identify and treat dandelions, clover, and chickweed early.

Catching these weeds early prevents major summer infestations. I time my spring treatment to tackle the first waves.

Water Thoroughly After Application

After spring application, irrigate lightly to dissolve the granules, then deeply water the root zone. This prevents burning while carrying nutrients and weed killers down to the roots.

Syringe the lawn to moisten the blades, but avoid runoff. Then soak the soil profile, typically applying 1-1.5 inches of water. Proper watering is key.

Follow these tips for well-timed spring St. Augustine weed and feed, maximizing control and growth. Monitor soil temp, green-up, and young weeds to optimize results.

Fall Weed and Feed Schedule

While spring weed and feed cares for emerging weeds, a fall application controls mature weeds while preparing St. Augustine for winter. Here are my top tips for perfect fall timing.

Apply 6-8 Weeks Before First Fall Frost

For the fall schedule, I recommend applying weed and feed 6-8 weeks prior to the average first frost in your area. This late summer to early autumn window boosts winter preparation.

Fertilization in early fall helps St. Augustine grass build strong roots before going dormant. Weed control also benefits from warm soil and air temps still conducive to herbicide efficacy and absorption.

Target weeds like dandelions at this stage before they go to seed. Time applications well before cold sets in.

Control Perennial Broadleaf Weeds

While spring targets young weeds, fall weed and feed helps control mature perennial broadleaf weeds like dandelions, clover, and wild violets. Hitting them in autumn helps weaken their overwintering root system.

Spot spraying severe weed patches may also be necessary. But a broad application in the fall window will weaken and thin many mature weeds.

Let Lawn Dry Before Heavy Frosts

When applying fall weed and feed, be sure to leave ample drying time before heavy frosts set in. This prevents frozen foliage from damaging the grass.

Don’t fertilize too late when cold weather is imminent. Allow at least 4 weeks between application and expected frost. Proper timing prevents winterkill.

Follow these tips for properly timed fall weed and feed on St. Augustine. Tackle those persistent broadleaf weeds and prep for winter while still in prime conditions. Proper timing optimizes results.

Frequently Asked Questions

Proper weed and feed application often raises common questions for homeowners caring for St. Augustine lawns. Here I’ll address some of the key FAQs I regularly receive.

How often should I apply weed and feed to St. Augustine grass?

I recommend applying weed and feed to St. Augustine twice per year for the best results – once in early spring and again in early fall. Spring targets young weeds, while fall controls mature weeds. An annual split application provides balanced care. Avoid overapplying, as St. Augustine is sensitive to overfertilization.

What weeds does weed and feed work best on?

In spring, target early crabgrass as well as chickweed and clover. Fall applications work well on mature dandelions, wild violet, and clover. Combining pre and post-emergent herbicides controls a broad spectrum. Spot spray severe patches separately.

Are there any tips for applying weed and feed safely?

Follow label directions carefully and sweep any product off impervious surfaces. Apply on a calm, dry day avoiding exposure to rain, and water in thoroughly after application. Wear protective gloves when handling weed and feed products. Check St. Augustine tolerance before applying at higher rates.

Let me know if you have any other questions! Proper weed and feed application keeps your St. Augustine lush and weed-free.


Properly timed weed and feed applications are crucial for nourishing a lush, weed-free St. Augustine lawn. As we’ve covered, ideal timing depends on several factors like temperature, growth stage, moisture, and target weeds.

In spring, apply 4-6 weeks after green-up when the soil has warmed and young crabgrass and broadleaf weeds are emerging. In fall, treat 6-8 weeks before your first expected frost while weather is still conducive to herbicide efficacy and translocation to perennial weed roots.

Follow label directions carefully and water in thoroughly after application. Take care to allow adequate drying time before any expected frosts. Split programs attack weeds at different life stages while powering growth when it matters most.

While it takes some finesse, properly timed weed and feed leads to a thriving St. Augustine lawn. Evaluate your climate and target weeds, then plan split spring and fall treatments accordingly. With the right schedule, your grass will flourish weed-free with no danger of burn. Healthy turf starts with products timed to perfection.

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