Best Weed and Feed for St. Augustine Grass

When choosing weed-and-feed products for your lawn, you’ve got to be careful as some herbicide additives can have side effects on different turfgrasses. I always want to check the active ingredient and the NPK ratio to make sure they’re safe and appropriate for St. Augustine grass and the type of weeds I’m targeting.

The best weed and feed for St. Augustine grass lawns is Scotts Southern Tripple Action Turf Builder. Alternative products you can also use are Spectracide Weed and Feed, Pennington Ultragreen Southern Weed and Feed, and Ferti-Lome Weed and Feed. I’ve reviewed them below in detail.

Best Weed and Feed for St. Augustine Grass

Weed and feed products comprise mineral ingredients that add nutrients to the soil as well as systemic or contact herbicides that kill weeds on your lawn. They’re available in either granular or liquid form.

The best weed and feed products for St. Augustine lawns are those that effectively get rid of weeds while simultaneously boosting St. Augustine turf growth.

Below, we detail some of the best weed and feed products, factoring in various benefits like the versatility of use, affordability, NPK ratio, and potency.

1. Scotts Southern Triple Action Turf Builder

• It is a 29:0:10 NPK fertilizer.
• It acts as an insecticide for your lawn.
• Kills dandelions, chickweed, and dollarweed.

Scotts Tripple Action weed and feed contains Atrazine, a herbicide that effectively gets rid of stubborn turf weeds like dandelions, dollarweed, and chickweed. It also infuses your lawn with nutrients that boost the turf’s capacity to withstand heat and drought.

Scott’s Turf Builder Southern Triple Action weed and feed is a 3-in-1 product that also contains Bifenthrin, an insecticide that kills common St. Augustine lawn pests like fire ants and chinch bugs. I found that it is best applied on St. Augustine grass after the third mowing of the growing season and shouldn’t be used during winter dormancy.

2. Ferti-Lome St. Augustine Weed and Feed

• 15:0:4 NPK fertilizer
• Controls crabgrass, sedge, spotted spurge, etc. in lawns
• Contains zinc and iron that green up your lawn.

Ferti-Lome St. Augustine Weed and Feed are specially formulated to get rid of common St. Augustine lawn weeds like Paspalum and Crabgrass. It works well as both a pre-emergent and post-emergent herbicide. This herbicide-cum-fertilizer has a 15:0:4 NPK ratio.

Ferti-Lome comprises 0.79% Atrazine, a potent herbicide that effectively kills several types of warm-season turf grass weeds. This weed and feed product is also laden with micro-nutrients like iron, zinc, and boron.

Take note though, that Ferti-Lome St. Augustine Weed and Feed is only half as powerful as Scott’s Southern Triple Action Turf Builder.

3. Spectracide Weed and Feed

Spectracide Weed and Feed is a ready-to-spray lawn treatment with an NPK ratio of 20:0:0. It consists of the following active ingredients:

• 2, 4-D dimethylamine salt- an auxin-type herbicide that effectively eradicates broadleaf weeds without affecting St. Augustine grass.
• Dichlorprop-p dimethylamine salt- a post-emergence herbicide that’s effective in controlling brush weeds like dandelion and clover.
• Mecoprop-p dimethylamine salt- a common broadleaf weed controller.

Depending on how healthy your St. Augustine lawn is, it may take a repeat application to completely get rid of clover and dandelion weeds from your lawn using Spectracide Weed and Feed.

You may also have to be patient, as the product may take up to four weeks to fully get rid of weeds, factoring in the turf conditions.

4. Sunniland St. Augustine Weed and Feed

It is a 20:0:6 NPK fertilizer

Sunniland St. Augustine Weed and Feed is an excellent choice for St. Augustine turfs because it can be applied both in the spring and in the fall. With an NPK ratio of 20:0:6, this weed and feed formulation for St. Augustine grass infuses lawn soil with ample amounts of nitrogen and potassium nutrients to spur healthy turf growth and disease resistance.

From my own use, I found that Sunniland Weed and Feed is unbeatable as a weed killer, as it effectively gets rid of a wide range of weeds like crabgrass and spurge.

Note that it Sunniland Weed and Feed for St. Augustine grass has no phosphorus, which means it may not be very suitable for a newly established lawn as a root-boosting fertilizer. I’d advise you to choose a high phosphorus content fertilizer for your turf after sodding such as Milorganite (6:4:0 NPK) or its alternatives.

5. Pennington Ultragreen Southern Weed and Feed

• 34:0:4 NPK fertilizer
• Kills henbit and clover in lawns
• Has 5% iron that makes grass greener

Pennington Ultragreen Southern Weed and Feed’s biggest selling point is that it’s both a quick-release and slow-release fertilizer. The fast-acting nitrogen will turn your St. Augustine turf into a lush green and dense lawn within a short period while the slow-release nitrogen ensures the turf stays fed for up to three months.

List of weeds it controls: henbit, clover, and chickweed.

Pennington Ultragreen Southern Weed and Feed is best applied during summer when St. Augustine is actively growing. You may, however, need to reapply it after a month if the weed problem on your St. Augustine lawn is severe.

6. Southern AG, 2, 4-D Amine Weed Killer

2, 4-D Amine Weed Killer by Southern Agricultural Insecticides is an effective herbicide against most broad leaf lawn weeds including poison ivy, clover, and dandelions. It contains other active ingredients that stimulate the growth of St. Augustine grass.

2, 4-D Amine Weed Killer is one of the most economical weed and feed products out there, with 1-4 pints being enough to cover up to an acre of St. Augustine turf.

What I found from my tests is that this Southern AG formulation is rather at eradicating oxalis weeds as they regenerate quickly via underground rhizomes.

7. Sta-Green Weed and Feed

• Kills up to 250 weeds
• Safe for St. Augustine grass
• 26:0:12 NPK fertilizer

Of all the weed control + fertilizer product on the market right now, Sta-Green Weed and Feed is arguably the most potent, as it can kill up to 250 different types of weeds. This product also works well on a wide variety of turfs, including St. Augustine lawns. When applied during the fall, it will protect your St. Augustine tough against extreme winter weather.

Sta-Green weed and Feed has an NPK ratio of 26:0:12, with the high potassium content ensuring your turf can effectively withstand diseases and dry weather. The only drawback against this product is that it’s ineffective when applied during the spring or the summer, which is St. Augustine’s active growing season.

Note: Weed and feed granules are tiny, herbicide-coated fertilizer pellets that stick onto weeds when applied on a wet lawn. Liquid weed and feed is usually diluted before being sprayed over dry or damp grass. These formulations promote a healthy, weed-free turf resulting in a thick St. Augustine grass lawn.

St. Augustine weed and feed schedule

The best time of the year to apply weed and feed product blends on St. Augustine lawns is during the growing season (spring-summer) when the grass is actively growing and the weeds are still young. You can also apply weed and feed that contains pre-emergent herbicides early in the spring before the weeds sprout.

Meanwhile, to ensure proper fertilizer timing (usually three weeks after the turf greens up), use a weed and feed that contains slow-release nitrogen. This type of weed and feed will still be releasing nitrogen into the soil for up to three months after it was originally applied as a weed killer.

Note: Some weed and feed products, like Sta-Green Weed and Feed are not meant to be applied during the spring or the summer.  

More information

• Dr. Chrissie Segars: Assistant Professor and Extension, Turfgrass Specialist at Texas A&M AgriLife Extension: Turfgrass Maintenance – Summer Annual and Perennial Weeds
• Gene R. Taylor II, Jason Gray, Texas A&M University Extension Turfgrass Specialists: Maintaining St. Augustinegrass