The two types of grass most commonly grown in Texas are Bermuda grass and St. Augustine grass. There are several variables to consider when determining when to apply lawn fertilizer in Texas. With eastern Texas getting far more rain than western Texas, and the north being colder than the south, environmental conditions are chief among these variables.
A soil test will determine which nutrients your Texas lawn is lacking, guiding you as to the type of fertilizer to apply. Barring that, turfgrass specialists with Texas A&M University suggest that you use a 3-1-2 or 2-1-1 in the spring. In the fall, apply a fertilizer with a 2-1-2 analysis.
Again, the soil test will determine how much fertilizer to apply. As a rule of thumb, never apply more than 1 lb. of nitrogen per 1,000 square feet of lawn area.
Gardeners in the panhandle should apply their fertilizer in April and September. In mid-Texas the ideal time to fertilize your lawn is in March and October. You will need to also apply a nitrogen-only fertilizer in June. If you live in south Texas, apply the complete fertilizer in February or March and again in October or November, with a nitrogen-only application in May and again in August.