When it comes to keeping your St. Augustine grass looking lush and healthy, applying a weed and feed product is essential. Not only does it provide essential lawn food, but it also helps control dandelion, henbit, and other grassy weeds that can quickly take over your turfgrass. If you’re dealing with unwanted weeds and brown patches on your lawn, a weed-and-feed can be the solution you need, especially during early spring when weeds start to sprout.

Applying these products to St. Augustine grass requires a bit of know-how. Since many broadleaf weed killers can harm this type of grass, it’s crucial to choose the right product and use the proper technique. In fact, only a few herbicides on the market are rated to treat St. Augustine without harming it, but most of them are weed-control products only — not weed-and-feed products. 

In this article, I’ll discuss how to apply weed-and-feed products to your St. Augustine grass to keep your lawn healthy and lush.

What Is St. Augustine Grass?

If you’re living in a warm, southern climate like Florida, St. Augustine grass is an optimal choice for your lawn. Its lush, green appearance and ability to thrive in the heat make it a go-to for homeowners wanting a yard that can handle those scorching summers. This grass creates a thick, carpet-like lawn that’s as attractive as it is resilient.

St. Augustine grass is known for giving your yard that rich, dark green color. It spreads easily, thanks to its horizontal stems, which help it fill in quickly and form a dense lawn. While it loves soaking up the sun, it can also manage in partially shaded spots, making it versatile for different areas of your yard. However, keep in mind that it’s not as tough as other grasses like fescue or bluegrass in withstanding cold weather.

Maintaining your St. Augustine lawn doesn’t have to be complicated. A balanced lawn fertilizer, like Scotts Turf Builder, can keep it looking healthy and green. Just be sure to watch out for common lawn weeds like crabgrass, chickweed, and dollarweed, which can sneak in if you’re not careful.

Weed and Feed Basics

Unless you live in a frost-free climate, you should stop using any fertilizers at least six weeks before your average first frost date. St. Augustine is a warm-season grass that goes dormant for the winter, and you don’t want to stimulate growth that a cold front could kill.

I recommend spring and summer applications of weed-and-feed products for these types of lawns.

The most common herbicide for St. Augustine lawns is Atrazine. However, use it at your own risk and with extreme caution, as Atrazine is nasty stuff. It is a possible cancer-inducing chemical that could also cause birth defects, and it shows up in alarming levels in drinking water. One look at the stern warnings on the label should make you think twice about putting it on your lawn. I’ll dig more into this chemical and it’s risks below.

person applying weed killer to a lawn

A healthy lawn is naturally weed-resistant. If you have a widespread weed problem, focus on keeping your lawn healthy or on replacing the unhealthy lawn with groundcover or planting beds. Weed-and-feed products contain both fertilizer and herbicide in one formulation. The combination can provide convenience but needs proper precautions.

When To Avoid Weed and Feed Products

Weed and feed products contain fertilizer and herbicides. The combination works well for reviving St. Augustine grass but carries some risk. Here are reasons to avoid putting weed and feed on St. Augustine grass:

  • It’s fall or winter. The fertilizer component can stimulate growth that is susceptible to frost damage. Instead, reserve weed-and-feed for the active growing seasons of spring and summer.
  • It’s six weeks or less before your average first frost date. Find your average first frost date from the Farmer’s Almanac, and don’t apply a weed-and-feed product in this six-week window. This way, you give your grass time to harden off before cold weather arrives.
  • There’s a drought or heat stress. Fertilizers can push growth that requires more water than the lawn is getting. This practice leads to grass burnout.
  • You’re overseeding. The herbicide component will inhibit the germination of grass seed. Wait until new grass is established before applying weed and feed.
  • Spreading sod. The chemicals can leach into the soil under the sod and inhibit root establishment. I recommend you let new sod take root for four to six weeks before applying a weed and feed product.
Today’s Homeowner Tips

Proper timing is important when using these combination products on St. Augustine grass. Pay attention to weather patterns and the health of your lawn.

The above timing recommendations are specific to warm-season grasses like St. Augustine. Cool-season grasses may have different guidelines, so always check the product label.

Problems With Atrazine (and What To Use Instead)

Atrazine, a herbicide often included in weed and feed products for St. Augustine grass, poses several risks that make it worth avoiding. The U.S. Environmental Protection Agency (EPA) labels Atrazine as a potential carcinogen and endocrine disruptor. Research links high exposure to increased cancer rates in people.

This chemical lingers in soil and groundwater, leading to contamination of drinking water sources nationwide. Moreover, Atrazine runoff contributes to toxic algae blooms in ponds, lakes, and other surface waters, posing a danger to pets and wildlife. Although many countries have banned Atrazine, it remains legal in the United States, though some states have imposed partial bans or restrictions.

Over the years, I transitioned away from Atrazine to safer options, such as corn gluten meal, vinegar, and plant-based herbicides. These have less environmental impact.

Given the health and environmental risks of Atrazine, avoiding it may be the wisest choice for you, your lawn, and your community. Talk to your lawn care company about chemical-free options or products without Atrazine.

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How To Maintain a Healthy Lawn

The best defense against weeds is a healthy, thriving lawn. Here are some tips:

  • Mow your lawn at the proper height for your grass type. Proper mowing height encourages deeper root growth. Keep mower blades sharp for clean cuts. 
  • Water thoroughly and infrequently to encourage deep root growth. Avoid frequent, light watering. Deep watering promotes stronger grass plants.
  • Dethatch and aerate your lawn annually to alleviate soil compaction. Thatch removal improves air and nutrient flow to the soil.
  • Apply a slow-release fertilizer two to three times a year. I recommend natural organic options like organic fertilizers break down slowly for steady feeding.
  • Overseed bare patches in spring and fall. Cover the new seed with straw. Seeding fills in thin and bare areas.
  • Raise your mowing height before the summer heat and lower it for fall. Adjusting height helps the grass stay healthy in changing weather.
  • Apply corn gluten meal in spring to deter new weed seedlings. Corn meal inhibits root formation in emerging weeds.

With proper cultivation, your lawn can out-compete weeds. Then spot treatments, or hand-weeding may be all you need for problem areas.

Final Thoughts on Weed and Feed Products

Using weed and feed products on your St. Augustine grass is a great way to keep your lawn looking lush and healthy. Timing is everything — spring and summer are your best bets for applying these products because your grass is actively growing and can benefit the most. Just be sure to skip the weed and feed in late fall or winter or during droughts/extreme heat to keep from stressing your lawn.

To keep weeds at bay, it’s important to maintain a healthy lawn. Regular mowing, proper watering, and the right fertilizing practices are key. Don’t forget about dethatching and aerating your lawn and overseeding when needed to help fill in any bare spots. With consistent care and the right products used at the right times, you’ll keep your lawn in top shape and enjoy a beautiful yard all year long.

FAQs About Applying Weed and Feed to St. Augustine Grass

When is the best time to apply weed-and-feed?

For St. Augustine grass, apply weed-and-feed during the active growing season of spring and summer. Avoid use in fall and winter. Discontinue at least six weeks before your average first frost.


How often can I apply weed-and-feed products?

You can apply most products every six to eight weeks during the growing season. Don’t exceed the labeled application frequency and annual use limits.


What precautions should I take when using weed-and-feed?

Read the label thoroughly and follow all instructions. Wear gloves, long sleeves, and closed-toe shoes when handling the product. Keep children and pets off-treated areas until the lawn is dry. Sweep any product that lands on driveways back onto the lawn to prevent runoff.


Are weed-and-feed products safe for the environment?

Some common herbicides in weed-and-feed products, like Atrazine, are linked to environmental harm. Some countries have banned the use of Atrazine as a result. Consider alternatives like corn gluten meal or natural weed killers instead.


Can I use weed-and-feed on newly laid sod or after overseeding?

Avoid using a weed-and-feed product on new sod or after seeding new grass. Wait four to six weeks for new sod to root before applying weed and feed. Allow new seedlings to fully establish before treatment as well.


Editorial Contributors
avatar for Coty Perry

Coty Perry

Expert Writer & Reviewer

Coty Perry is a lawn and garden writer for Today’s Homeowner. He focuses on providing homeowners with actionable tips that relate to the “Average Joe” who is looking to achieve a healthier and greener lawn. When he isn’t writing he can almost always be found coaching youth football or on some trail in Pennsylvania in search of the next greatest fishing hole.

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Laurie Engle

Expert Writer & Reviewer

Laurie Engle is a freelance writer who provides insights to homeowners on topics such as the home warranty industry, relocation issues, and real estate trends. As a licensed Realtor since 2001 Laurie has acquired extensive expertise in dealing with home warranty companies and navigating the intricacies of the real estate market. In addition to her commitment to helping clients with their home buying and selling needs, she maintains a sharp awareness of market dynamics, including property values, interest rates, and local regulations.

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