The weather, overall health of your turf grass, and soil will greatly affect the speed in which your grass grows. Lots of rain means your grass will need to be mowed more often. Periods of drought mean you will mow less frequently. But, the general rule of thumb is to try and remove around one third of the grass blade at each mowing. But why is this and how do you stick to it?
Grass plants have a “growing point” where the leaves or blades originate from. This growing point will stay close to the soil if the grass is mowed often and the rule of thumb is followed. If you let your grass grow too tall before mowing it, then this growing point will move up from the soil, reducing density, opening the door to weeds, and placing the growing point at risk of being chopped off by the mower. If the growing point is cut, the plant may not be able to recover. So, if you mow your St. Augustine grass to around 3 inches, you should mow it when it reaches between 3.5–4 inches. For Bermuda grass, when mowing to 2 inches, you should mow it when it reaches between 2.5-2.6 inches.
Check out Texas AgriLife’s Turf mowing recommendations for optimal mowing height for each type of grass. https://aggieturf.tamu.edu/answers4you/mowing.html And remember, deep infrequent watering is best for your landscape. Not only does it build deep, strong roots, it saves precious water too!