September in the South Carolina Midlands can still feel like summer. Bermudagrass, centipedegrass, and zoysiagrass may still be green, temperatures are still warm, and winter weeds probably aren’t the first thing on your mind.
But this is exactly when you need to start thinking about them.
Many of the weeds that show up as bright green patches in dormant lawns during the winter and early spring begin germinating in the fall. By the time you can see them, they’ve already become established.
That’s why fall pre-emergent is an important part of winter weed prevention in South Carolina. The goal isn’t to kill weeds you can already see. It’s to get ahead of weeds such as annual bluegrass (Poa annua), henbit, chickweed, and other winter annuals before they become a problem.
For homeowners throughout Columbia, Lexington, West Columbia, Chapin, Irmo, and the surrounding Midlands, that makes early fall an important part of the annual lawn care cycle.
For established warm-season lawns in the Midlands, September is an important period for fall pre-emergent applications targeting winter annual weeds.
But we wouldn’t recommend choosing an arbitrary date on the calendar and assuming it’s right for every lawn, every year, or every product.
Pre-emergent needs to be applied before the target weeds germinate. Weather conditions, soil temperatures, the weeds being targeted, turf type, and the herbicide being used can all affect application decisions.
That’s why timing matters so much.
Wait until winter weeds are growing throughout the lawn, and you’ve missed the opportunity to prevent those particular plants. At that point, you’re dealing with established weeds and may need an appropriate post-emergent treatment instead.
This is one of the most common points of confusion about pre-emergent.
Your lawn can look perfectly fine when the application is made.
That’s actually the idea.
Winter annual weeds begin their life cycle before many homeowners realize there’s a problem. They germinate during favorable fall conditions and can continue developing as your warm-season turf begins slowing down and eventually enters winter dormancy.
Fall pre-emergent is designed to interrupt that cycle.
At Sprout Tech Turf Solutions, we’re not only looking at what your lawn needs today. We’re also thinking about what’s likely to happen next.
In the video, Andy shows the Specticle® FLO used by Sprout Tech Turf Solutions and explains why the company puts so much emphasis on fall pre-emergent.
Specticle FLO is a premium professional herbicide, but the product itself is only part of the equation. Effective weed prevention requires the right product, the right rate, the right timing, and an application program designed around the lawn and the season.
That’s the difference between simply putting a product on the lawn and having a weed-control strategy.
The exact weeds controlled depend on the herbicide being used, so homeowners should always refer to the product label. However, several common winter annual weeds are worth knowing about in South Carolina.
Annual bluegrass, commonly called Poa annua, is one of the most noticeable winter grassy weeds in warm-season lawns.
It can appear as lighter or brighter green patches and eventually produces distinctive whitish seedheads.
Poa becomes particularly obvious once bermudagrass, centipedegrass, or zoysiagrass has turned brown for winter.
That’s when homeowners sometimes discover that the green they see in January isn’t their lawn thriving.
It’s weeds growing through dormant turf.
If you’ve ever noticed small purple flowers scattered across a lawn in late winter or early spring, there’s a good chance you’ve seen henbit.
The important thing to understand is that henbit didn’t suddenly appear when those flowers became visible.
Henbit is a winter annual that can germinate in the fall, survive through the cooler months, and become much more noticeable as it matures.
So if you wait for the purple flowers before thinking about henbit, you’re reacting to an established weed rather than preventing it.
Chickweed is another winter annual broadleaf weed that can become established during cooler weather.
It often takes advantage of favorable conditions and thinner areas of turf. Like henbit and Poa annua, its life cycle illustrates why winter weed control begins well before winter.
Lawn burweed is particularly frustrating because homeowners may not realize it’s present until the plant develops the sharp burs that make walking barefoot through the lawn unpleasant in spring.
But the plant has been growing long before those burs become noticeable.
Again, the timing of the problem and the timing of prevention are two different things.
This is where fall weed prevention becomes especially relevant in the Midlands.
Bermudagrass, centipedegrass, and zoysiagrass are warm-season grasses. As temperatures fall, they eventually enter dormancy and lose their green color.
Winter annual weeds operate on a different schedule.
They can remain green while the surrounding warm-season turf is brown or tan, making even a relatively small weed problem highly visible.
As Andy puts it in the video:
“You don’t want to be the guy with green in your brown lawn this winter.”
It’s funny, but it’s also a pretty accurate description of what happens.
A brown dormant lawn isn’t necessarily unhealthy. That’s part of the normal life cycle of warm-season turf. Bright green patches scattered throughout it, however, may be winter weeds.
This is also why fall pre-emergent shouldn’t be confused with the pre-emergent applications used earlier in the year.
Both are preventative weed-control strategies, but they’re aimed at different weed cycles.
Spring pre-emergent is commonly used to get ahead of warm-season annual weeds such as crabgrass before they germinate.
Fall pre-emergent targets susceptible weeds that germinate during the cooler portion of the year.
If you’d like to understand more about the timing earlier in the growing season, read our When Should You Apply Pre-Emergent in West Columbia, SC? article.
The important takeaway is that one pre-emergent application doesn’t provide year-round weed prevention. Different weeds germinate at different times, which is why weed control needs to follow the seasonal life cycles of the weeds we’re trying to manage.
The names provide a pretty good clue.
Pre-emergent herbicides are used before susceptible target weeds become established.
Post-emergent herbicides target weeds that have already emerged.
If you’re looking at a mature weed in your lawn and wondering whether putting down pre-emergent will kill it, the answer is generally no. That’s not the job of a pre-emergent herbicide.
A year-round lawn care program may use both strategies at different times: prevent what we can and appropriately control what still emerges.
Timing is one of the most important parts of successful pre-emergent weed control.
If the target weed has already germinated and become established, applying a pre-emergent isn’t going to make that existing plant disappear.
That doesn’t mean there’s nothing that can be done.
An appropriate post-emergent herbicide may be an option for weeds that have already emerged, while a pre-emergent application may still be useful for susceptible weeds that haven’t yet germinated. The appropriate approach depends on the weed, turf species, product, and conditions.
This is why identifying what’s actually growing in the lawn matters.
Many pre-emergent herbicides require rainfall or irrigation after application to move the active ingredient into the area of the soil where weed seeds germinate.
But this isn’t something homeowners should guess about.
Always follow the label for the specific herbicide being applied. Watering requirements, application rates, approved turf species, timing, and restrictions can vary from one product to another.
The label—not a generic lawn care schedule found online—should be the final authority.
Not always.
Depending on the product and weed-control program, a second fall application may be appropriate to extend control later into the season. Clemson Cooperative Extension notes in its warm-season turf recommendations that some pre-emergence programs may call for a second application approximately eight to ten weeks after the initial treatment.
That doesn’t mean every lawn should automatically receive the same treatment eight weeks later.
It means pre-emergent has a period of effectiveness. The product being used, application rate, target weeds, turf species, weather, and label directions all need to be considered.
Effective weed control is a program, not a one-time spray.
This is one situation where homeowners need to be particularly careful.
Pre-emergent herbicides work by interfering with the establishment of susceptible germinating plants. Depending on the product, that can include grass you’re intentionally trying to grow from seed.
If you’re planning to seed or overseed, don’t assume a fall pre-emergent application is compatible with that plan.
Check the herbicide label for seeding restrictions or work with a turf professional who understands how the different applications interact.
For established warm-season lawns, Sprout Tech Turf Solutions builds weed prevention into the overall treatment program based on the turf species, season, and conditions.
There’s a tendency to think lawn care ends once summer growth begins slowing down.
It doesn’t.
Your warm-season grass may be approaching dormancy, but weeds follow their own life cycles. Decisions made in September and throughout the fall can have a major impact on what you see growing through your dormant lawn this winter and next spring.
That’s why fall pre-emergent deserves attention before there’s an obvious weed problem.
If you remember having Poa annua, henbit, chickweed, or other winter weeds last year, don’t wait for them to reappear before thinking about weed control.
At Sprout Tech Turf Solutions, our lawn care program changes throughout the year because your lawn—and the weeds competing with it—change throughout the year.
Fall pre-emergent is one part of that strategy. By getting ahead of susceptible winter annual weeds before they become established, we can help keep dormant warm-season lawns cleaner through the cooler months and into spring.
If you’re in Columbia, Lexington, West Columbia, Chapin, Irmo, or another community in the South Carolina Midlands, request a quote from Sprout Tech Turf Solutions and let us build a lawn care program around what your turf needs throughout the year.
When it comes to winter weeds, the best time to think about them is before you can see them.
