Texas summer is a legitimate stress test for any lawn. Sustained heat above 100°F, low rainfall, and alkaline soils create a combination of problems that no other region faces quite the same way. Bermuda grass and St. Augustine — the two grasses that dominate Texas lawns — are tough, but they need specific management to make it through July and August without permanent damage.
Take-all root rot (TARR) is caused by the soil fungus Gaeumannomyces graminis and is the leading cause of unexplained lawn decline in Texas St. Augustine lawns. It's widely misdiagnosed as drought stress because the symptoms — yellowing, thinning, and irregular dieback — look similar. The key difference is that TARR doesn't respond to watering; you can irrigate heavily and the lawn continues to decline.
To confirm: pull up an affected plant. The roots will be short, dark brown to black, and rotted — compared to healthy white roots extending 3-4 inches. The stolons (above-ground runners) may have dark lesions. As Texas A&M AgriLife Extension's turfgrass pathology program notes, root discoloration is the single most reliable diagnostic indicator separating TARR from abiotic stress.
Take-all root rot is most active in spring and early summer when soils are wet, though symptoms often aren't visible until summer when the damaged root system can't support the plant through heat stress. The disease favors high soil pH (common in Texas), poor drainage, and excessive nitrogen applied in spring.
Treatment is challenging. The most effective approach is applying peat moss (sulfur-containing peat from Canada, pH 3.5-4.0) at 1.5 cubic feet per 100 square feet to acidify the soil surface and suppress the fungus. Fungicides containing azoxystrobin applied at the first sign of symptoms can slow progression. Avoid high nitrogen fertilization in spring.
If your St. Augustine or Bermuda lawn looks yellowed between the leaf veins while the veins themselves remain green — a pattern called interveinal chlorosis — you're almost certainly seeing iron deficiency, not disease and not drought. This is extremely common across Texas due to naturally alkaline soils (pH 7.5-8.5) that bind iron into forms plants can't absorb. Texas A&M's Soil, Water and Forage Testing Laboratory confirms that at pH levels above 7.5, iron precipitates into ferric oxide compounds that grass roots cannot take up regardless of total soil iron concentration.
You can have iron in your soil and iron-deficient grass simultaneously — alkaline pH makes the iron chemically unavailable. Adding regular fertilizer won't fix it. The solution is applying chelated iron directly to the lawn — a form of iron that remains available even at high pH.
Foliar application (spray directly on the grass blades) gives the fastest visible response. Granular chelated iron mixed into the soil works more slowly but can address deeper root-zone deficiency. The lawn will green up within a week of a foliar application.
Texas summer watering requires more precision than most of the country. The combination of high temperatures, low humidity, and often-alkaline soils that drain poorly creates a counterintuitive situation: you can overwater and underwater simultaneously in different parts of the same yard.
The target for most Texas lawns in summer is 1 to 1.5 inches per week applied in two deep sessions (Wednesday and Saturday, for example). Daily light watering keeps the surface perpetually wet without putting water into the root zone, promotes disease, and creates salt buildup near the surface on alkaline soils. According to University of Minnesota Extension's turfgrass watering guidance, infrequent deep irrigation consistently outperforms daily shallow watering for root depth development and drought tolerance — a principle that applies with even greater force under Texas heat stress.
Water before sunrise. In Texas summer heat, irrigation run during the day loses 30-50% to evaporation before it reaches the soil.
Stage 2/3 water restrictions: Many Texas municipalities impose watering restrictions in summer. Know your local restriction schedule — most allow twice-weekly watering on designated days, which happens to align with the agronomically ideal schedule anyway.
Scalping — mowing Bermuda grass very short (0.5-1 inch) once in early spring when the grass first starts to green — removes the dead winter growth and allows sunlight to warm the soil and reach new growth. It accelerates green-up by 2-3 weeks and removes thatch that would otherwise block fertilizer and water penetration.
The window: when Bermuda is 50% green and nighttime temperatures are consistently above 50°F. In Houston and San Antonio, that's typically late February to early March. In Dallas and Fort Worth, early to mid-March.
St. Augustine should not be scalped — it doesn't respond the same way and scalping damages the stolons that spread new growth.
Texas summer heat demands higher mowing heights than most homeowners use. A taller canopy shades the soil, reduces surface temperatures, retains soil moisture, and lets the plant photosynthesize more efficiently under stress.
Take-all root rot, iron chlorosis, chinch bugs, and drought stress all cause yellowing. They need different treatments. Get an accurate diagnosis before you treat.
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