Knowing when to fertilize St Augustine grass is the key to a thick, green, and healthy lawn. This essential seasonal feeding guide will walk you through the best times and methods to nourish your turf.
St. Augustine is a popular warm-season grass, loved for its lush appearance and tolerance to heat. But to keep it looking its best, it needs the right nutrients at the right time. Feeding it incorrectly can lead to weak growth, disease, and damage. Let’s break down the annual schedule so you can plan your lawn care with confidence.
When To Fertilize St Augustine – Essential Seasonal Feeding Guide
Your fertilization schedule revolves around the grass’s natural growth cycles. St. Augustine is actively growing in the warm months and goes dormant (turns brown) when temperatures drop. You should only fertilize during its active green growth period.
The Best Time to Start Fertilizing
Begin your fertilization schedule in late spring, after the last frost has passed and the soil has warmed up. A good rule of thumb is when daytime temperatures consistently stay above 70°F and the grass is fully green and actively growing. For most regions, this is around April or May.
- Watch for green-up: Don’t fertilize while the lawn is still dormant or just starting to wake up. The roots can’t absorb the nutrients yet.
- Soil test first: If possible, conduct a soil test. This tells you exactly what nutrients your soil lacks, preventing over-application.
The Core Growing Season Schedule
During the peak of summer, your St. Augustine is growing rapidly. It needs regular feeding to support that growth and maintain its color and density.
- Late Spring (First Application): Apply a balanced, slow-release nitrogen fertilizer.
- Early Summer (Second Application): Follow up 6-8 weeks later with another feeding.
- Mid-Summer (Third Application): A third application 6-8 weeks after that sustains the lawn through heat stress.
Always follow the specific instructions on your fertilizer bag for rates and timing. Over-fertilizing is a common mistake that can harm your lawn and the environment.
The Final Fall Feeding
Your last fertilization is crucial. Apply a fall fertilizer in early to mid-fall, about 6-8 weeks before your regions first expected frost date. This timing is vital.
- Use a low-nitrogen, high-potassium fertilizer: Look for a product labeled for “winter guard” or “fall feed.” The potassium helps strengthen the grass’s roots and cell walls, improving its cold tolerance and disease resistance over the winter.
- Do not fertilize too late: Fertilizing too late in the fall with high nitrogen can promote tender new growth that will be killed by frost, weakening the entire lawn.
What Type of Fertilizer Should You Use?
Choosing the right product is as important as the timing. Here’s what to look for:
- Slow-Release Nitrogen: This is non-negotiable for St. Augustine. It feeds the grass gradually over time, providing even growth and reducing the risk of fertilizer burn. It also minimizes nutrient runoff.
- N-P-K Ratio: The three numbers on the bag (e.g., 15-0-15, 10-10-10). For most summer feeds, a balanced ratio or one slightly higher in nitrogen works well. For the fall, a ratio like 5-10-30 is ideal.
- Contains Iron: St. Augustine benefits from iron, which enhances its deep green color without causing excessive growth spurts.
Avoid “Weed and Feed” Products
Be cautious with combination herbicide-fertilizer products. St. Augustine is sensitive to many common herbicides, especially during hot weather. It’s often safer to fertilize and control weeds separately.
How to Apply Fertilizer Correctly
Proper application ensures your lawn gets the benifit without waste or damage. Follow these steps:
- Mow: Cut your lawn a day or two before applying fertilizer. Bag the clippings to get a clean surface.
- Calibrate Your Spreader: Whether using a broadcast or drop spreader, set it to the rate recommended on the fertilizer bag. This prevents uneven application.
- Apply to Dry Grass: Fertilize when the grass blades are dry to prevent them from sticking and burning.
- Water Thoroughly: After application, water the lawn lightly. This helps move the fertilizer granules off the grass blades and into the soil. About 1/4 inch of water is sufficient.
Regional Considerations for Timing
Your local climate will shift the calendar slightly. Here’s a general guide:
- Deep South (Florida, Coastal Gulf): Start earlier (March-April) and may have a longer season, sometimes requiring 4 feedings. The final fall feeding is later, around October.
- Transition Zone & Southeast (Georgia, Carolinas, Texas): Typical schedule begins in May, with 3 summer feedings and a final fall feeding in September or early October.
- Subtropical (Southern California): Can follow a similar schedule to the Deep South, adjusting for local rainfall patterns.
Signs You Are Fertilizing Wrong
Your lawn will tell you if the schedule or product is off. Watch for these warnings:
- Yellowing quickly after feeding: Could indicate fertilizer burn from over-application or applying to wet grass.
- Excessive thatch buildup: Over-fertilizing, especially with fast-release nitrogen, can cause the grass to grow too quickly and contribute to thatch.
- Increased disease or pest problems: Lush, over-fertilized growth is more suceptible to fungal diseases like brown patch and attracts insects like chinch bugs.
- Weak growth or pale color: This likely means the lawn isn’t getting enough nutrients or the soil pH is off, locking up available food.
Essential Lawn Care Partners to Fertilization
Fertilizing alone won’t guarantee a perfect lawn. These practices work hand-in-hand with your feeding schedule:
- Watering: St. Augustine needs about 1 inch of water per week, including rainfall. Deep, infrequent watering is best to encourage deep roots.
- Mowing: Keep your mower blade high. St. Augustine should be mowed at 3.5 to 4 inches tall. This height shades the soil, conserves moisture, and discourages weeds.
- Aeration: If your soil is compacted, core aerate in the early summer. This helps water, air, and fertilizer reach the root zone more effectively.
Frequently Asked Questions (FAQ)
Can I fertilize St. Augustine in the winter?
No. You should never fertilize St. Augustine during winter dormancy. The grass is not actively growing and cannot use the nutrients, which can then pollute waterways or harm the dormant grass.
How often should I feed my St. Augustine lawn?
Typically, 3-4 times during the active growing season is sufficient. A common schedule is late spring, early summer, mid-summer, and early fall with a special fall formula.
Is it okay to fertilize St. Augustine in hot summer heat?
Yes, but with caution. Use only slow-release fertilizer and apply it during a cooler spell if possible, following with good watering. Avoid fertilizing during extreme drought or heat stress unless you can irrigate properly.
What is the best St Augustine fertilizer schedule for my area?
Contact your local county extension office. They provide free, scientifically-backed lawn care calendars tailored to your exact location and soil conditions, which is the most reliable method.
Can I use the same fertilizer as my neighbor with Bermuda grass?
Not always. While needs can overlap, Bermuda often tolerates more frequent feeding and different herbicides. It’s best to choose a product specifically recommended for St. Augustine’s needs, particularly its sensitivity.
Following this essential guide for when to fertilize St Augustine grass takes the guesswork out of lawn care. By aligning your feeding with the seasons, choosing the right products, and applying them correctly, you’ll provide the steady nutrition your lawn needs to thrive. Remember, a consistent and thoughtful approach yeilds the best results, giving you a robust and beautiful turf season after season.