Does St Augustine Grass Spread?

As a lifelong gardener and landscaper, I’ve worked with all kinds of turfgrasses over the years. But few spark as much curiosity as St. Augustine grass and its reputation for aggressive spreading. Maybe you’ve noticed those thick, verdant lawns in your neighborhood, the ones that seem to creep steadily outwards, sending their wiry stolons onward in search of new ground to claim. Believe it or not, St. Augustine’s habit of lateral growth is both a blessing and a curse for homeowners.

On one hand, St. Augustine’s ability to spread rapidly allows it to fill in bare patches, choke out weeds, and repair damage quickly – advantages that explain its popularity across the southern United States. But left unchecked, St. Augustine can encroach on flower beds, vegetable gardens, and more. Even neighbors may find a creeping carpet of St. Augustine invading their turf!

The key is understanding what makes St. Augustine spread so prolifically and how to keep its growth under control. In this article, we’ll explore how fast St. Augustine can spread laterally under ideal conditions. We’ll discuss the specific factors that trigger rapid growth and examine different strategies to contain St. Augustine within defined lawn areas. Whether you’re dealing with gaps in your existing St. Augustine lawn or hoping to prevent its spread into unwanted zones, you’ll find the insight you need to strike the right balance.

So let’s get growing! Read on to master the art of managing St. Augustine grass and its infamous spreading habit.

How Fast Does St. Augustine Grass Spread?

As a warm season grass, St. Augustine thrives during hot, humid months. When conditions are ideal, this aggressive turf can expand at an astonishing rate. In my experience, a healthy St. Augustine lawn can easily spread a foot or more outward each month during peak growing periods.

Of course, lateral spread slows down when temperatures cool, moisture levels decline, or other environmental factors become less than optimal. But even during dormancy, St. Augustine continues to gradually broaden its reach via subsurface rhizomes. Once awakened by spring’s arrival, your St. Augustine will be primed for another season of rapid lateral growth.

St. Augustine’s Speed Depends on Its Growth Habits

What makes St. Augustine capable of spreading so quickly across lawns and landscapes? The answer lies in its habits of above-ground and subsurface growth.

St. Augustine spreads laterally primarily through stolons. Stolons are stems that creep along the soil surface, rooting at nodes to form new plants. As each segment develops roots and leaves, it becomes a new plant genetically identical to the parent.

Below ground, St. Augustine also expands via rhizomes – horizontal, underground stems that send up new vertical shoots. Together, these above and below ground stems allow St. Augustine to efficiently colonize areas well beyond its original planting zone.

I’ve seen single St. Augustine plants grow over ten feet wide in just one season thanks to prolific stolon and rhizome activity! Clearly, this grass earns its reputation as a fast and determined spreader.

Fertile, Moist Soil Accelerates Spread

During my time as a landscaper, I noticed certain conditions reliably turbocharge St. Augustine’s rate of spread. Rich, fertile soils with abundant nutrition provide the fuel for rapid stolon and rhizome growth. Ample moisture is also key, as drought stressed grass puts growth on hold.

Proper mowing height plays a role too. By cutting St. Augustine too short, you remove its food factory and force the plant to focus energy on lateral spread to survive. Letting grass grow taller channels more resources into root development rather than stolon growth.

Likewise, overwatering seems to accelerate spread. Soggy soils encourage shallow rooting, and without deep roots anchoring it, St. Augustine puts more energy into lateral expansion.

If you notice your St. Augustine invading flower beds or your neighbor’s yard, stepped up fertility and excessive irrigation may be the culprits. Adjusting your maintenance practices can help throttle back the spread.

Strategies for Slowing St. Augustine’s Advance

While St. Augustine’s rapid growth allows it to thrive, containment becomes necessary in cultivated landscapes. Based on my hands-on experience, here are some effective strategies for controlling St. Augustine’s spread:

  • Mow at 3 or 4 inches to strengthen roots over stolons. Never cut below 2 inches.
  • Water deeply and infrequently. Avoid frequent, light watering.
  • Improve drainage with organic matter to discourage shallow roots.
  • Use edging to sever rhizomes and contain growth within beds.
  • Consider applying growth regulators to stems to inhibit spread.

It takes some effort to keep St. Augustine in check. But the benefits of lush, vigorous turf are well worth the extra diligence required. Just remember: conditions that favor root growth over stems and stolons are key for controlling your St. Augustine lawn.

Spreading St Augustine Grass

What Conditions Cause St. Augustine To Spread?

St. Augustine grass thrives in warm, humid environments like the American south. This aggressive grass capitalizes on favorable growing conditions to expand via above and below ground stems. Through years of experience, I’ve learned to recognize the specific factors that trigger St. Augustine’s most prolific spreading.

Heat and Humidity Propel Growth

As a C4 photosynthetic plant originally from tropical regions, St. Augustine relishes heat. Optimal day temperatures for vigorous growth range from 80-95°F. Nights should remain above 70°F. St. Augustine will continue growing in 100+ degree weather, whereas cool season grasses shut down.

Humidity is also integral to St. Augustine’s performance. Leaf surfaces must remain moist for efficient photosynthesis. St. Augustine flourishes when relative humidity exceeds 60%.

St. Augustine lawns in southern states like Florida and Texas enjoy an ideal climate. Long summers with ample warmth and humidity allow for luxurious green growth and aggressive lateral spread via stolons and rhizomes.

Northern grasses simply can’t compete with St. Augustine’s summer production under these conditions. Even winter dormancy can’t curtail its steady advance via subsurface rhizomes.

Soil Fertility Powers Vigorous Growth

During my time as a gardener in Florida, I observed extremely rapid spreading across lawns planted with St. Augustine. Upon soil testing, invariably these lawns showed elevated nutrient levels.

St. Augustine thrives in fertile soils abundant in nitrogen, phosphorus and iron. Adequate potassium and micronutrients are also essential for vigorous growth and spread.

By ensuring pH stays between 6.0-7.0, you guarantee nutrients remain plant-available. Routine fertilization replaces nutrients used for rapid growth.

When St. Augustine has all the nutritional tools it needs, the turf channels its energy into above and below ground stem production. Stolons and rhizomes surge outward seeking new territories to colonize.

Moisture Levels Influence Growth Habits

St. Augustine performs best when soil moisture is maintained without extremes. As a landscaper, I found overwatering triggered rampant spreading across lawns. Excess irrigation leads to shallow rooting, forcing St. Augustine to focus less on developing deep roots and more on lateral spread.

Conversely, severe drought stresses St. Augustine, causing it to concentrate on survival rather than spread. Growth slows considerably.

The ideal approach is deep, infrequent irrigation. This encourages deeper rooting for better heat and drought tolerance. Less energy goes toward stolon and rhizome growth.

Proper Mowing Height Affects Growth Habits

During my early days mowing lawns, I didn’t realize cutting St. Augustine too short forced it to morph from a bunch-type grass into a sprawling carpet. Removing too much leaf tissue causes St. Augustine to sacrifice vertical growth in favor of lateral spread.

Cutting higher – 3 to 4 inches – leads to improved density and deeper roots. Longer leaf blades allow better photosynthesis. St. Augustine responds by focusing less on stolon growth.

So in summary, factors like heat, humidity, fertility, moisture and mowing height all influence whether your St. Augustine concentrates on roots or lateral spread. Adjust these elements correctly to find the right balance.

How To Slow Down St. Augustine Spread?

As a landscaper, I constantly receive requests to “reign in” homeowners’ invading St. Augustine lawns. This robust grass happily marches beyond its boundaries, smothering flower beds and vegetable gardens in its path.

While St. Augustine’s vigorous spreading habit makes it resilient, containment strategies are necessary for a neatly manicured landscape.

Through years of trial and error, I’ve discovered proven cultural practices that throttle back St. Augustine’s rate of lateral growth. By tailoring these maintenance techniques, you can still enjoy the benefits of a lush, verdant lawn while keeping your St. Augustine in check.

Mowing Height Matters

Out of all cultural factors, mowing height is one of the most influential for controlling St. Augustine spread. As a general guideline, you should maintain St. Augustine at 3 or 4 inches tall. Here’s why this mowing height is ideal:

  • Longer leaf blades allow for more efficient photosynthesis. With a larger food factory, the plant focuses energy on developing deep roots rather than lateral spread.
  • A taller canopy shades the ground, reducing soil temperatures. This slows stolon growth.
  • More leaf area means deeper roots to support additional transpiration. Deep roots decrease the need for rhizome spread.

Conversely, cutting too short starves St. Augustine of its food factory. The plant is forced to morph from an upright bunch grass into a horizontally spreading carpet.

Aside from mowing high, also be sure to sharpen mower blades regularly. Ragged cuts create openings for disease and stimulate the grass to expand laterally.

Water Deeply and Infrequently

Overwatering is another culprit behind rapid St. Augustine spread. Too much moisture leads to compressed, poorly aerated soil that restricts deep rooting. The grass compensates by expanding sideways via stolons and rhizomes.

The solution is less frequent but deeper irrigation. Allow the top half inch to inch to dry between watering. Then apply a thorough soaking to moisten the soil 4-6 inches down.

This encourages deeper rooting and stronger turf with less tendency to spread out. Drier soil at the surface also inhibits stolon growth.

Improve Drainage

St. Augustine thrives in moist, fertile soils. But those same conditions can also cause problems with poor drainage, compaction and accelerated lateral spread.

Adding organic material like compost improves moisture retention while maintaining pore spaces for drainage and air circulation. Topdressing with compost or an organic fertilizer provides slow-release nutrition without overfeeding.

You can also aerate compacted areas to alleviate surface pooling and improve permeability. Healthy drainage keeps soils moist without being waterlogged.

Edge Beds

Installing a sturdy border between lawn and garden areas serves multiple purposes. Burying edging several inches deep severs wandering rhizomes before they sneak into planting beds. This forms an underground barrier complementing the visible border.

Edge material choices include plastic, aluminum, steel, bricks, stones and timber. I prefer steel – it offers durability and flexibility for curving borders. Even sharp V-cut trenches can deter subsurface spread.

Whatever edging you choose, regular maintenance like trenching or trimming back encroaching grass remains necessary. But a good edging system gives you a fighting chance against St. Augustine’s stealthy advance!

Consider Growth Regulators

In extreme cases, growth regulating products can be selectively applied to areas where St. Augustine continues spreading despite cultural controls.

Growth regulators like trinexapac-ethyl (T-Nex) inhibit enzymes for stem and stolon growth. This forces the grass to channel its energy into roots instead.

Use caution with growth regulators, as improper applications can damage turf. Always follow label directions. Conservative use alongside cultural practices leads to the best results.

Maintain, Don’t Restrain

Rather than fighting St. Augustine’s natural habit of spreading, work with it by fine-tuning maintenance practices. Nourish roots over rhizomes and stolons. Set limits but avoid over-restraint.

With adaptive care, you can continue enjoying the unique benefits of St. Augustine while keeping expansion manageable. A lush, vigorous lawn and elegant landscape design aren’t mutually exclusive!

What Are The Benefits Of St. Augustine’s Spread?

While St. Augustine’s vigorous spreading habit requires maintenance, this growth trait also provides distinct advantages. Through years of experience landscaping coastal lawns, I’ve come to appreciate the special assets that St. Augustine’s lateral expansion lends.

Let’s examine some of the key benefits you can expect from this grass’s propensity to spread.

Quickly Fills in Bare Spots

St. Augustine’s dense network of above and below-ground stems allows it to quickly cover open areas in a lawn. Damaged areas from pet urine spots, heavy foot traffic, or dead patches rapidly green up again as stolons creep across bare soil. Rhizomes also emerge from the edges to accelerate infill.

This energetic re-sodding ability saves the homeowner time and money compared to re-seeding. You can rely on St. Augustine to actively repair itself, provided growing conditions are favorable.

Chokes Out Weeds

An aggressively advancing St. Augustine lawn leaves little room for weeds to take hold. The thickening mat of grass chokes out competition, denying weed seeds the light and space needed to germinate.

St. Augustine even secretes allelopathic chemicals from its roots that chemically inhibit weed seed germination. This biological weed barrier complements the physical suppression from the expanding grass canopy.

This weed-controlling tendency means less need to apply herbicides. Allowing the St. Augustine to fill in is often the best weed management strategy.

Forms a Dense, Wear-Resistant Turf

The tangled network of stems that St. Augustine sends out across the lawn results in a dense, tight-knit turf. This vigor and concentrated growth habit allows St. Augustine to withstand moderate foot traffic without damage.

Kentucky bluegrass lawns, for example, easily show footsteps and compressed areas as their vertical growth habit leaves crowns exposed. Meanwhile, St. Augustine’s horizontally aligned leaf tissue better tolerates being walked across.

Pet activity and play also diminish once the stems interweave to create a wear-resistant living carpet. St. Augustine’s durability suits its popularity in family neighborhoods.

Adapts and Spreads to Diversify the Lawn

Within St. Augustine grass, there are several cultivars bred for unique traits. And due to stolons freely spreading and mingling, a lawn of one variety will naturally incorporate genetics from surrounding cultivars over time.

For example, shade tolerant Seville St. Augustine may creep into areas of drought hardy Raleigh. Their stolons intertwine to create a diverse turf blended from multiple cultivars.

This adaptation allows the lawn to incrementally acquire beneficial characteristics. The result is a patchwork quilt of blended grasses uniquely adapted across microclimates.

Spreads to Choke Weeds and Fill Gaps

While St. Augustine’s spread requires maintenance, it’s this same trait that allows the grass to resist weeds, recover from damage, and blend cultivars. Embrace the spreading habit positively as a protective mechanism.

With care not to overfeed and overwater, you can enjoy both the beauty and resilience of St. Augustine. Its vivacious growth keeps your lawn lush, green and weed free.

FAQ About Spreading St. Augustine Grass

Does St. Augustine Grass Spread Above Ground?

Absolutely. St. Augustine’s primary method of lateral spread is via above ground stems called stolons. Stolons are horizontal shoots that creep along the soil surface. At nodes where they contact the ground, they send down adventitious roots to establish new plants.

Over time, these extending stolons interweave to form a solid mat of grass. I’ve seen aggressive St. Augustine cultivars spread several feet in all directions over a single growing season thanks to proliferating stolon growth.

So in short, stolons are the main avenue for St. Augustine to spread rapidly across your lawn. Keep an eye out for these long, wiry above ground stems radiating out from the parent plant. If you see stolons expanding into unwanted areas, adjustments to your maintenance regime may be needed.

Does St. Augustine Grass Spread Underground?

St. Augustine doesn’t rely solely on above ground stolons for propagation. This grass also uses below ground stems called rhizomes to spread laterally.

Rhizomes form a network of horizontal stems down in the soil. Unlike stolons, rhizomes lack nodes and leaves. But they do contain meristematic tissue capable of generating new upward-oriented shoots.

Through branching and growth, rhizomes expand the subterranean footprint of St. Augustine steadily outward. Then new vertical shoots emerge outside the bounds of the original planting area as rhizomes extend the edges.

The combination of aggressive above ground stolon spread and below ground rhizome activity makes St. Augustine a highly successful colonizer. Even during winter dormancy, rhizomes continue advancing the subterranean frontier.

Is St. Augustine Considered An Invasive Grass?

While St. Augustine grass can certainly invade and overrun landscape beds, vegetable gardens and neighboring lawns, it is not categorized as an invasive plant from an ecological perspective.

True invasive grasses displace and disrupt native plant communities. St. Augustine remains confined to cultivated landscapes like residential lawns and commercial properties. Although capable of spreading several feet per year via stolons, it does not pose a threat to native ecosystems.

With proper cultural controls like mowing height adjustment, edging, and diligent confinement of runners, St. Augustine can be maintained as a non-invasive lawn. Let it grow unchecked and you’ll likely hear complaints from the neighbors! But managed correctly, St. Augustine makes a fine turfgrass.

The bottom line: this aggressive spreader requires vigilance to prevent encroachment. But ecologically, it is no threat to displace native plants in natural environments. With care, St. Augustine is a well-behaved, non-invasive lawn grass.


After years of firsthand experience nurturing St. Augustine lawns, I’ve learned to work with this grass’s innate habit of spreading rapidly. With the right maintenance approach, you can enjoy thick, resilient turf while keeping growth contained.

St. Augustine’s lateral expansion through stolons and rhizomes enables quick fill-in of bare areas, natural choking out of weeds, and blending of beneficial traits from different cultivars. Yet left uncontrolled, the grass can encroach where it’s not wanted.

The key is finding the sweet spot through proper mowing, watering, edging and fertilization. Nourish the roots and rhizomes while restricting the stolons. Maintain St. Augustine without trying to completely restrain it.

With adaptations like mowing higher, irrigating deeply, and setting physical barriers, you can strike a balance between vigorous spread and excessive encroachment. Take advantage of St. Augustine’s natural vigor while guiding it politely back into place.

St. Augustine’s reputation as an aggressive spreader arose for good reason. But don’t let that dissuade you from enjoying this lush, resilient turfgrass. With proper care and containment, you can happily embrace all the benefits of St. Augustine!

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