The KPRC Radio Gardenline Tip By Randy Lemmon For 04-01-04 Printer-Friendly Version
March Mart Mania
Here in Houston, the vast majority of the lawns are of the St. Augustine variety. There are some Bermuda-based lawns, some are Zoysia and very few (if any at all) are Centipede.
Most people with St. Augustine yards have bits and pieces of Bermuda, but for those that are being overwhelmed with Bermuda, the question I usually get is "How do I get rid of the Bermuda in my St. Augustine?"
The obvious answer is to kill it, till it and replace it with new sod. But that's usually on for the extreme cases where the Bermuda is absolutely solid. In all the other cases where there is a mix of Bermuda and St. Augustine, cultural practices will help the St. Augustine win the battle.
Nine times out of ten the answer is in the MOWING. If you will mow as tall as you can, or as tall as your lawn mower will allow, the St. Augustine will almost always crowd out the Bermuda. Conversely, if you want to accelerate the Bermuda, mow shorter and shorter and more often and the Bermuda will win the battle.
The reason for this juxtaposition in MOWING HEIGHT works like this: Bermuda can't grow in shade, and 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 your yard at all. However, I promise your lawn will be a richer green and thicker texture than your shorter-cutting-neighbors. I call it the "Bring Your Neighbor Up to Your Level" debate.
And there are some added benefits to growing taller-than-normal St. Augustine. First, your irrigation/watering will last longer with the grass tall. There are a couple of reasons for this. One is that tall grass supports deeper roots. Deeper roots have more water available to them when the water is in the deeper reaches of the soil.
The second reason is more biotechnical. The grass blades have stomata on them to transpire CO2, oxygen, and water vapor. They open in the morning and close when they get their fill of CO2. If the plant has more stomata exposed (like from taller grass), then the stomata collect CO2 in all of them. At the same time, soil microbes are releasing CO2 in their normal metabolism. At the same time, CO2 is heavier than air and tends to remain close to the ground, especially in the morning and especially in tall grass where the wind needs to blow harder to blow the CO2 away.
When you combine all these events, you get the stomata getting more CO2 because there are more of them, and because the amount of CO2 is denser near the stomata due to the taller grass and microbial off gassing. So 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.
So, taller grass needs even less water than short grass for those two reasons. Yes, I know that was way more technical than most everyone needed. But it does show you how much I like researching this kind of stuff for you.
Finally, there are two more absolutes that you need to keep in mind when trying to weed-out the Bermuda from your St. Augustine. First, it can not suffer from drought damage - such as in a yard ignored during the summer while you are on vacation - and secondly it cannot suffer from Chinch Bug damage either. Here's that tip sheet just in case,
< http://www.950kprc.com/gardenline-chinchbugs.html >
Until next week, here's to Great Gardening from the GardenLine, heard exclusively weekend mornings from 8 to noon on Talkradio 950 KPRC.
Until next issue, here's to
Great Gardening from the GardenLine, heard
exclusively weekend mornings from 8 to noon
on Talkradio 950 KPRC.