Of all the warm-season grasses growing in North Texas yards, St. Augustine is the most recognizable — and the most misunderstood. Its wide, flat blades, lush blue-green color, and ability to handle partial shade make it a popular choice throughout Arlington, Grand Prairie, and the surrounding DFW area. But St. Augustine is also the most chemically sensitive common lawn grass in this region, and treating it like Bermuda is one of the fastest ways to turn a beautiful lawn into a patchy, discolored mess. Here’s what makes this turf different and what it actually needs to look its best.
Why St. Augustine Behaves Differently
St. Augustine (Stenotaphrum secundatum) spreads only by stolons — above-ground runners — not underground rhizomes like Bermuda. This means it recovers from damage more slowly and is less able to fill in bare spots on its own. It prefers well-drained soil and thrives in full sun to partial shade, making it the go-to choice for yards with mature trees where Bermuda would thin out and die.
The most common variety in North Texas is Floratam, which offers good chinch bug resistance and handles heat well but is notably more cold-sensitive than Bermuda. A hard freeze that barely phases a Bermuda lawn can push St. Augustine into extended dormancy or cause real winter injury in northern DFW. This cold sensitivity shapes the entire treatment calendar for this grass.
Fertilizing St. Augustine: What It Wants and When
St. Augustine has a respectable nitrogen appetite, but not as aggressive as Bermuda. Over-fertilizing — especially with high nitrogen in late summer and fall — is one of the leading causes of problems with this turf. Excess nitrogen late in the season drives lush, tender new growth that’s highly susceptible to two things: cold damage and brown patch fungus.
A healthy St. Augustine fertilizer program for North Texas looks like this:
- Spring application: Once the lawn fully breaks dormancy and nighttime temps stay above 55°F, a balanced nitrogen application jumpstarts growth. Mid-April through May is typically ideal in DFW.
- Summer feeding: A split application in June and again in August maintains color and density through peak heat. Iron supplementation is highly effective for St. Augustine — it delivers the deep green color without the growth flush of additional nitrogen.
- Fall cutoff: Stop nitrogen applications by early September at the latest. This is where many homeowners go wrong. Late nitrogen on St. Augustine is a direct invitation to brown patch disease and cold injury.
The Herbicide Sensitivity Issue
This is where St. Augustine treatment gets genuinely different — and where using the wrong product can cause lasting damage. St. Augustine is sensitive to herbicides that Bermuda tolerates with no problem, and vice versa. Key points every St. Augustine homeowner should know:
- Atrazine is safe; many broadleaf products are not: St. Augustine is one of the only common warm-season grasses that can handle atrazine applications. Ironically, common broadleaf herbicides containing 2,4-D that are safe on Bermuda can injure St. Augustine at normal rates, especially during summer heat stress.
- MSMA is a no: Products in the MSMA/DSMA family cause significant injury to St. Augustine and should never be applied to this turf type.
- Celsius WG is one of the few post-emergent options that handles both grassy and broadleaf weeds safely on St. Augustine. Application timing and rate still matter — heat and drought stress change what the turf can handle.
The practical takeaway: read the label carefully, and when in doubt, have a professional handle post-emergent applications on St. Augustine. The cost of re-sodding an injured lawn far outweighs the cost of a professional treatment. Our full program for St. Augustine and other North Texas grasses is detailed on our weed control and fertilizer services page.
Pre-Emergent on St. Augustine
The good news: St. Augustine handles the standard pre-emergent herbicides — prodiamine, pendimethalin, and dithiopyr — well. Spring pre-emergent targeting crabgrass should go down when soil temps hit 55°F, typically February–March in DFW. Fall pre-emergent for cool-season weeds targets the September–October window when soil temps drop below 70°F.
One caveat: atrazine (which is safe for St. Augustine post-emergent) also has pre-emergent properties and is sometimes used in fall for both pre-emergent and residual broadleaf control on this turf type. This isn’t a standard choice for all lawn programs but is an option worth knowing about.
The Big Three St. Augustine Problems and How Treatment Ties In
Beyond weeds, three issues disproportionately affect St. Augustine in North Texas, and all three are connected to fertilization and treatment timing:
- Brown patch fungus: The most common St. Augustine disease in DFW, showing up as circular brown patches in fall and spring. High nitrogen going into fall is the primary trigger. Preventive fungicide applications and stopping fall nitrogen early are the most effective management tools.
- Chinch bugs: These tiny insects suck plant fluids and cause irregular brown patches in summer, often confused with drought stress. Healthy, well-fertilized turf is more resistant, but infestations need targeted insecticide treatment.
- Take-all root rot: A soil-borne fungal disease that causes irregular decline, often in spring. Connected to soil pH and organic matter levels — another reason soil health matters as much as surface treatments.
St. Augustine vs. Bermuda: Why You Can’t Use the Same Program
If you moved from a Bermuda lawn to a St. Augustine lawn (or have both in adjacent areas), the adjustment can be jarring. What worked perfectly on Bermuda may injure St. Augustine. The fertilizer timing is different. The safe herbicide list is different. The disease risks are different. Recognizing that your lawn’s grass type defines every treatment decision is the most important shift any North Texas homeowner can make. For a deeper look at how Bermuda responds to these same inputs, our post on Bermuda grass weed control and fertilizer lays out the contrast clearly.