Is St Augustine Grass a Weed?

As a longtime gardener and lawn care enthusiast, I’m quite familiar with St. Augustine grass. This warm-season turfgrass is a popular choice across the Southern United States thanks to its adaptability and lush green blades. However, St. Augustine’s aggressive growth habit also lands it on some gardeners’ lists of undesirable “weeds.”

So, is St. Augustine grass considered a weed? The answer isn’t quite black-and-white. This grass exhibits some potentially weedy traits, like spreading rapidly and crowding out other plants. But it also offers benefits like good disease resistance and shade tolerance. Ultimately, whether you see St. Augustine as a weed or worthwhile lawn grass depends on your landscaping goals and tolerance for its vigor.

In this article, I’ll share my personal experience growing and managing St. Augustine grass. You’ll learn about its identification, growth habits, and invasiveness. I’ll also provide tips to control its spread if that’s a concern in your lawn. Finally, I’ll discuss some pros and cons to help you decide if St. Augustine is right for your yard or more trouble than it’s worth.

By the end, you’ll have a better understanding of this turf’s weed potential and make an informed decision about using it in your own landscape. So whether you already grow St. Augustine or are considering it for a new lawn, read on to get the full story! Let’s start by looking at exactly what makes St. Augustine grass distinctive.

Why Some Consider St. Augustine a Weed?

St. Augustine grass is well-adapted to hot, humid environments, which makes it a popular turfgrass choice across the Southern United States. However, some gardeners view St. Augustine as a problematic weed due to its aggressive growth habits and ability to invade flower beds, gardens, and neighboring lawns. There are a few key reasons why this grass gets labeled as a weed by some.

Aggressive Growth Habit

In the right growing conditions, St. Augustine grass can grow quite vigorously. As a warm season perennial grass, it actively spreads both above and below ground during the growing season. St. Augustine forms dense mats of stolons, stems that creep along the soil surface, allowing it to quickly spread laterally. It also produces rhizomes below ground that expand its reach.

This dense and rapid growth allows St. Augustine to crowd out neighboring plants with ease. In my experience managing gardens and lawns in Florida, containment becomes difficult once St. Augustine is established. The grass ably invades flower beds and the root system expands under walkways, patios and fences. Its vigor enables it to encroach on weaker plants and even overtake entire lawns.

Invasive Tendencies

A major concern with St. Augustine grass is its potential to invade new areas, acting as an exotic weed. St. Augustine propagates itself through above and below ground stems, allowing it to spread well beyond its original planting site. Bird and animal activity also enables the grass to spread via seed dispersal.

Once established, St. Augustine grows in thick mats that choke out native plants not adapted to competing with this aggressive grass. Here in Florida, I’ve seen St. Augustine escape confinement and overrun natural areas and parks. It displaces native grasses and wildflowers, reducing biodiversity. This earns it a spot on some invasive species watch lists.

Ability to Choke Out Other Grasses

St Augustine Grass

St. Augustine’s vigor also poses issues for lawns with a mix of grass species. Over time, St. Augustine’s dense growth and lateral spread allow it to overwhelm and choke out companion grasses like Bermuda and zoysia. The end result is often a monoculture St. Augustine lawn.

To create a mixed species lawn using St. Augustine, I learned that careful management practices are required. Regular mowing, edging, dethatching and aggressive division helps curb St. Augustine’s spread. Herbicides or physical removal of encroaching stolons may also be needed to maintain balance. Even with diligent care, however, St. Augustine tends to dominate over time.

In summary, St. Augustine’s rapid spread, invasiveness and ability to choke out other plants lead some gardeners to view it as a weed. Maintaining boundaries and balance requires a commitment to frequent maintenance and containment measures. For those desiring a lower maintenance landscape, less aggressive grass alternatives certainly exist. However, as we’ll explore next, St. Augustine also offers some compelling benefits.

Benefits of St. Augustine Grass

While St. Augustine grass exhibits some weedy traits, it also offers benefits that help explain its popularity, especially in the hot and humid regions of the south. As someone who has grown St. Augustine grass for over a decade, I’ve come to appreciate some of its advantages as a lush, soft turf.

Thrives in Hot, Humid Climates

St. Augustine grass thrives in the warm temperatures and high humidity found across zones 8-10. As a heat-loving grass species, it relishes summer’s high temperatures when cool-season grasses struggle and go dormant. I’ve found St. Augustine stays vibrant and green throughout Florida’s long, hot summers when few other turf options persist.

The grass also appreciates the high humidity prevalent in the south. St. Augustine actually performs best when relative humidity levels surpass 60 percent. Hot, muggy climates provide an ideal environment for lush St. Augustine growth.

Tolerates Salt, Shade and Drought

Beyond heat and humidity tolerance, St. Augustine exhibits other environmental adaptability that makes it well-suited for southern landscapes:

  • Salt Tolerance – St. Augustine withstands salt well, including saltwater flooding and salt accumulation in soils. This enables it to thrive along coastal areas.
  • Shade Tolerance – The grass tolerates moderate shade, enabling it to grow under light tree cover. Its shade tolerance exceeds that of Bermuda and zoysia grass.
  • Drought Tolerance – Once established, St. Augustine exhibits reasonable drought tolerance thanks to its deep root system. While it performs best with ample moisture, it can withstand temporary dry spells.

These tolerances give St. Augustine an advantage in urban and seaside landscapes common in the south. The turf remains resilient through heat waves, moderate shade and periodic dryness or salt exposure better than most alternatives.

Few Pest or Disease Problems

Compared to other warm season grasses, St. Augustine experiences relatively few serious pest or disease issues. It has better natural disease resistance than Bermuda and zoysia varieties. The dense mat of stolons resists weed invasions, so herbicides are rarely needed. Chinch bugs can be an issue, but prompt treatment controls outbreaks.

In my experience, a well-maintained St. Augustine lawn stays lush and healthy with minimal pesticide use. Its vigor and natural disease resistance keep it looking great with limited chemical inputs once established. This saves time and money compared to constant spraying and treatment required by some grasses.

While St. Augustine has some weedy tendencies, its environmental adaptability, lush texture, and low maintenance needs in warm climates explain its popularity across the south. With proper care and containment, it can make an attractive, resilient lawn. Next, we’ll look at some frequently asked questions to further understand its risks and rewards.

FAQs About St. Augustine Grass

Over my many years of growing and managing St. Augustine grass, I’ve fielded plenty of frequently asked questions about caring for this turfgrass. Here I’ll address some common St. Augustine grass FAQs, drawing from my hands-on experience to provide helpful insights.

Is St. Augustine grass hard to control?

St. Augustine’s aggressive spreading habit definitely makes containment a challenge. Given the right growing conditions, the grass can certainly overtake flower beds, gardens, and weaker neighboring turf. However, proper mowing, edging, and division practices make St. Augustine’s spread manageable.

Here are some tips I’ve learned for keeping St. Augustine grass growth contained:

  • Mow frequently, at the highest recommended height for your variety. This discourages lateral spread.
  • Install physical borders like metal edging between lawn and garden beds. This acts as a root barrier.
  • Vigilantly prune back stolons that creep beyond borders. Catch them before they root.
  • Aggressively divide dense patches by slicing inward from the edge to encourage outward growth.
  • Consider growth-regulating herbicides if other methods fail to restrain spread.

With diligent attention to mowing, edging, pruning and division, St. Augustine’s potential to overrun nearby areas can be controlled. Proper cultural practices prevent it from becoming a unruly weed.

Does St. Augustine grass spread quickly?

St. Augustine’s ability to spread rapidly is what earns it a reputation for being weedy. Given adequate moisture and nutrients, St. Augustine spreads aggressively via above-ground stolons and below-ground rhizomes. It easily outpaces the growth rate of common grasses like Bermuda and zoysia.

In fact, St. Augustine can fully fill in an area through lateral spread within one growing season under optimal conditions. I’ve seen it spread several feet outward within a single season when irrigated and fertilized well. So yes, St. Augustine’s potential growth rate is quite substantial.

However, responsible management that encourages deep root growth over lateral spread keeps the grass’ vigor in check. Mowing high, watering deeply but infrequently, and limiting nitrogen fertilizer prevents it from spreading too quickly.

Is St. Augustine grass good for all lawns?

While St. Augustine offers benefits like lushness, shade tolerance and drought resistance, it isn’t the ideal grass for every landscape due to its aggressive growth.

Here are some factors to consider before planting St. Augustine:

  • Climate – St. Augustine thrives in warm, humid climates only. It fails in cool, arid regions.
  • Sun Exposure – Partial shade tolerance makes it suited for light shade, but dense shade will thin it out.
  • Maintenance Level – Expect to mow, prune and divide frequently to control rapid spread.
  • Mixed Grasses – St. Augustine tends to choke out Bermuda, zoysia and other companion grasses over time.
  • Invasiveness – Its spreading nature can overtake flower beds, curb strips and neighboring lawns if unchecked.

While a top performer in the south, St. Augustine may prove overly aggressive and high maintenance for other regions or low-care landscapes. Consider your climate and lawn goals carefully.

I hope these insights help explain St. Augustine’s strengths and weaknesses to determine if it fits your unique needs. Maintenance practices and containment regimen must match the grass’ vigor to prevent weed-like overgrowth.


After growing St. Augustine grass for over a decade in Florida, I’ve experienced both its benefits and challenges firsthand. While at times unruly, overall I’ve found it to be a lush, attractive turf when properly managed.

St. Augustine certainly exhibits aggressive growth tendencies that require an attentive maintenance routine. However, for warm southern climates its environmental adaptability can’t be matched by many alternatives. With adequate mowing, edging and division practices, the vigor that earns it a reputation as a weed can be contained.

The keys to success are realistic expectations and commitment to proper care. St. Augustine’s rapid lateral spread and shade tolerance may overwhelm the unprepared. But knowledgeable gardeners find it rewarding with modest inputs of time and effort. Before planting, consider your regional suitability, site conditions and readiness to implement control measures.

If these factors align, St. Augustine can likely thrive. Embrace its lively expansion and champion its deep verdant hues. With a bit of diligent care, your lawn will flourish as a showcase, not a weed. For those in cooler climates or seeking lower maintenance grasses, steer clear. But here in the south, I continue to value St. Augustine as the pinnacle of lush, resilient lawns.

In closing, weigh St. Augustine’s pros and cons against your own climate, site and needs. When properly managed in its ideal habitat, this heat-loving grass can create a vibrant landscape showpiece. Yet, without control measures its vigor crosses over to weedy. Take my experiences shared here to make the right choice for your lawn.

Scroll to Top