Yellow St. Augustine: Check for Thatch, Not pH

A Texas St. Augustine lawn at pH 7.8 stays yellow despite iron and nitrogen. pH 7.8 is high but not extreme; nutrient lockup unlikely. The real culprit: thatch.

St. Augustine builds thick thatch (dead stems/runners) that blocks water and fertilizer from reaching roots. Check: cut a 6" core; look for brown, felt-like layer >½" thick between green blades and soil.

If thatch >½": rent a dethatcher, run in multiple directions. Lawn will look damaged but recovers quickly. Then fertilize (late spring–early fall for warm-season grass) and water deeply twice weekly (45 min) on sand—3x in extreme heat.

Resources: thatch photos at OldHouseWeb, Versicolor.