Applying ‘Weed and Feed’ Products to St. Augustine Grass

Few weed-and-feed products are safe to use. (arousa/Getty Images)

As you’ve likely discovered, many broadleaf weed killers also harm St. Augustine grass. There are a few herbicides available that are rated for St. Augustine, but most of them are weed control only, not weed and feed.

A couple of thoughts about weed-and-feed products:

Be sure to check warning labels for any product you choose to use, some can be more harmful to you. (groveb/Getty Images Signature)

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 can be killed by frost. Weed-and-feed products are best reserved for spring and summer in these types of lawns.

The most common herbicide for St. Augustine lawns is Atrazine. Simply put, Atrazine is nasty stuff. It’s known to cause cancer and birth defects, and it’s showing up at 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!

A healthy lawn is naturally weed-resistant. If you have a widespread weed problem, focus instead on getting your lawn healthy, or on replacing the unhealthy lawn with groundcover or planting beds.

Further Reading


  1. I use Expert St. Augustine weed and feed, and it does a great job. It’s by Expert and it’s just for St. Augustine grass, it will state on the bag, St. Augustine. After the St. Augustine weed and feed is down for about two months, I use the following mixture.

    Lawn Care Recipe (mix all items and put into a sprayer connected to hose)
    One full can of regular Cola pop (any kind-no diet soda)
    One full can of beer (no light beer)
    1/2 Cup of Liquid dishwashing soap (do NOT use anti-bacterial dishwashing liquid)
    1/2 Cup of household ammonia
    1/2 Cup of mouthwash (any brand)
    1/2 -1 Cup of soaked water from steel wood pads
    1/2 cup of Espsom salts (Use Epsom Salt on your lawn and in your garden)
    You will notice bushier plants and brighter color blooms and your lawn will be thicker and greener. Sulfur and magnesium are vital to seed germination, production of chlorophyll and the conversion of sunlight into food. You can sprinkle the Epsom Salt in your garden around rose bushes, tomato plants, pepper plants, evergreens, azaleas, and rhododendrons, always water thoroughly after applying to get the salt into the soil at the roots. You will not have to worry about over using Epsom Salt in your yard and garden as most of the sulfur and magnesium will wash away. The salt will also keep many bugs away from sensitive plants and will also kill grubs in your yard and garden. Sprinkle with Epsom Salt on soil and work in before seeding lawn. The magnesium and sulfates help to germinate the seeds and make them stronger and healthier. You can also do this when you are starting plants for the garden from seeds.)

    Magnesium is:
    * A critical mineral for seed germination.
    * Vital to the production of chlorophyll, which plants use to transform sunlight into food.
    * An aid in the absorption of phosphorus and nitrogen, two of the most important fertilizer components.
    Sulfur, the other major component of Epsom Salt, is also an important plant nutrient.

    Sulfer may:
    * Contribute to chlorophyll production.
    * Make the primary nutrients (nitrogen, phosphorus and potassium) found in most fertilizers more effective.

  2. Hi Julie-

    I have an area in my yard (Houston) where grass does not grow well. Each year, I replace the soil and add new sod, spray for grubs, etc., but it always starts to flourish, then dies, ending up as brown and hard ugliness.

    Question: the area in question is lighted with a nighteime flood light. Would this nightime light affect the growth cycle and inhibit it rooting properly?

  3. My long established St. Augustine lawn (in Mobile, AL) appears to be afflicted with “SAD” – St. Augustine Decline. Internet sources indicate the only way to fight this viral desease is to plant plugs of resistant strains – specifically: Floratam, Floralawn, Raleigh, and Seville. I have not been able to find a place in the Mobile, Alabama area that sells any of these varieties. Do you know where I could get some? Thanks!

  4. I have an established st. augustine lawn in terrell, texas. Unfortunately my lawn is over run with weeds. What household products can’t I use to weed & feed my lawn?

  5. I live in central Arkansas just northwest of Little Rock.

    I have a very large lawn, St Augustine grass that was probably planted in the late ’70’s. Now, a broadleaf weed has taken over part of the front lawn, north side, and the entire east side. The south and east sides are still lush, dark green and so soft. What should I use to kill the weeds, then what should I do to prepare for and re-seed the damaged areas?

    According to the Texas aggie information, my grass would probably be Florentine, considering the date it was probably started.

    Please respond. I would so hate to lose the rest of my grass.

    Thank you


  6. I live in coldest part of Canada. My back yard is full of weed, unfortunately all kind of weed. How do i get rid of it. I used so much weed control so far, works for just a few days and comes back in strong. will you advise please?

  7. I live just north of Fort Worth and have an acre. It is a mixture of St. Augustine and Bermuda in the front yard with Bermuda and just plain prairie grass in the back yard. What can I mix in a 20 gallon sprayer to put weed control on the whole yard at one time that will not harm the st. Augustine but still get weed control?

  8. I live the North Texas and accidentally put Vigoro 28-0-3 Weed and Feed on my St Augustine ? Will it die? What should I do?

  9. I’m slowly losing my St. Augustine grass. It was put down a little over three years ago. I’ve treated the lawn for grub, treated it for brown patch and may have stopped those problems. I would like to put down a winterizer and Pre-emergent for fall. Where can I find 5-10-20 in Mobile, AL.
    Thanks for your advice,
    Barbara Sharp

  10. I live in Augusta Ga and have St Augustine grass. I currently have a bug that is black w/wings and has a orange line down each side of its wing. it with fly or hop as you walk through the grass. it makes the blades of the grass rusty brown. I was told its a spittle bug but I don’t see any picture of it looking like one. What is it & how do I treat it ?
    thank you

  11. Hello, I’m from Texas and I love Saint Augustine grass. I now reside in Joliette, Quebec Canada. Cou you possibly tell me if I can have the variety floralawn here?

    I was told that that I have possibly two different kinds of bugs and I have a few varieties of weeds. I’m going crazy, please try to answer this note. I’m really going nuts and the professionals that have come to my home have only killed my grass.


  12. Since going fully organic 6 years ago I have had to learn how to let go of my OCD lawn care! I’ve learned to enjoy the flowers of dandelions…pulling them before they seed. And clover is not the problem for me that it was before when I see the kiddos pulling it and eating a few of the tasty leaves knowing that it won’t harm them! Thank you for your dedication to organic methods!

  13. I have been watering my St. Augustine Grass as It need help after the Drought in S. California affected a once lush lawn .I can see it is regrowing but certain area’s where the Grass once grew is now gone and the soil is now bare. What can I do to help the grass spread quicker ,Thanks for any advice.

  14. I re- seeded my lawn last year, germination results are extremely disappointing.
    Presently I see a lot of crab grass , what should my action be?
    I live in New Jersey.



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