
The reason is Bermuda can’t grow in shade — taller St. Augustine will shade the slower growing Bermuda. Yes, you still have to mow once a week, but if your neighbors don’t come up to your level, it is going to look like you don’t mow at all. However, I promise your lawn will be a richer green with a thicker texture than your shorter-cutting-neighbors. I call it the “Bring Your Neighbor Up to Your Level” debate. And there is an added benefit to growing taller-than-normal St. Augustine. You won’t need to irrigate as frequently. First, because tall grass supports deeper roots which have more water available to them far down in the soil. Grass blades have microscopic pores (stomata) to transpire carbon dioxide (CO2), oxygen and water vapor. The stomata open in the morning and close when they get their fill of CO2. Since taller grass has more stomata exposed, it more readily collects CO2 released by soil microbes. And, as CO2 is heavier than air and tends to remain close to the ground, it’s harder for wind to blow it away in taller grass. Therefore, tall grass gets more CO2 because it has more stomata and because the amount of CO2 is denser near the stomata. And, as a consequence, the stomata close off earlier in the day shutting off the transpiration of water vapor from the plant and allowing the plant (and soil) to retain water better.