Ridding St. Augustine of Bermudagrass
The following was written by my friend Randy Lemmon of
radio station KPRC 950 AM in Houston. Great show called GardenLine.
For more great articles from Randy,
In Texas, the vast majority of the lawns are of the St. Augustine variety.
There are some Bermuda-based lawns, however, along with some of Zoysia, and
very few (if any) Centipede. Most
people with St. Augustine yards have bits and pieces of Bermuda, but some
are overwhelmed with it. The obvious answer to removing Bermuda is to kill
it, till it and replace it with new sod. But that's usually just for extreme
cases where the Bermuda is absolutely solid. In most cases ... where there
is a mix of Bermuda and St. Augustine ... cultural practices will help St.
Augustine win the battle. Simply mowing properly is the answer nine in 10
times. If you mow as tall as your mower will allow, the St. Augustine will
almost always crowd out the Bermuda. Conversely, if you want to accelerate
the Bermuda, mow shorter and more often — then the Bermuda will win.
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.
A second reason is more biotechnical.
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.
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