This is essentially a re-do of the permanent tip sheet already posted on the GardenLine page at ktrh.com but with some added info on herbicides.
Few things are more frustrating that having unwanted Bermuda grass infiltrate your St. Augustine lawn. It seems to take over in no time at all, so it's best to deal with the problem as quickly as possible.
The first and most important step to take is to start mowing your St. Augustine taller than you already are. The taller St. Augustine is, the more it shades the lower-growing Bermuda. If you don't have your lawn mower set at its highest level, raise it today.
Second, keep the lawn well-fertilized and well-watered. For GardenLine listeners, that simply means following my schedule. Bermuda loves to take advantage of a stressed-out environment, while the St. Augustine will thrive in a well-maintained environment.
Third, if those techniques have little or no effect — or if the Bermuda seems to be getting thicker or stronger — there is an herbicide treatment known as liquid atrazine. Regular GardenLine listeners and newsletter subscribers might wonder how I could recommend such a product. Stay with me here. I absolutely detest weed-and-feed products that contain granular atrazine, because it kills nearby tree roots and poisons groundwater supplies. Atrazine, in the granular form, moves very quickly in the soil, but liquid atrazine, because it's a topical treatment, does not move and is not an environmental hazard.
Ironically, liquid atrazine will still need the addition of a surfactant to make the herbicide do its job properly. If you've been reading my weekly e-mail blasts, or if you have a copy of my new book "1001 GardenLine Questions," you already know the importance of using surfactants.
You should also know that atrazine doesn't necessarily "kill" Bermuda. It just stuns it for a couple of weeks — hopefully long enough to allow properly cared-for St. Augustine to overwhelm the sickly Bermuda. Currently, there are no herbicides that will kill only Bermuda without affecting the St. Augustine, too. (I know ... I mentioned one several weeks ago, but it turns out the information I got and passed along to you was flawed.)
Herbicides like Roundup that kill both grasses could also be used effectively, if you don't mind cleaning out the entire area after the kill, backfilling with some enriched topsoil, and allowing nearby grass to fill back in over time.
Besides high mowing, there's another practice can help keep Bermuda at bay. Since Bermuda tends to thrive in areas getting too much water, you could extend your irrigation times a bit. Lawns that are watered weekly, instead of daily, and mowed at the highest setting, are known to choke out Bermuda.
Ironically, Bermuda will also take advantage of a drought-stricken lawn. That's because such lawns tend to go into a dormant state quicker under the stress and respond quicker once provided with ample moisture. So, consistency in irrigation, mowing, and fertilizing will be the key.
If you like Bermuda grass and don't want the St. Augustine, then think about reversing almost everything we just talked about, especially lowering the mower deck. I should note, too, that if you want Bermuda to thrive, you really need to change your lawn mower to a "reel" mower. They cut the grass in an over-the-top fashion. The standard rotary mower isn't actually designed for Bermuda grass.
Plants 'N Things, 3900 Highway 36 South
For the first time ever, we are taking GardenLine to Brenham!
We will be at Plants 'N Things on Highway 36, just south of Brenham. It's a great opportunity to learn about this garden store, where they know what they are doing and with a staff that loves to help with gardening questions.
This visit is being sponsored by our friends at Nitro-Phos, and they are opening up their prize closet for us. I know we will have weed killers and surfactants to give away, plus fire ant killers and more. And, we'll do a drawing for a free bag of Nitro-Phos Super Turf. You have to register win, and we will do drawings every half hour 12:30-2 p.m. You have to be present to win.
By the way, note that we are starting this event an hour later than normal, because it will take me a little time to get to Brenham after I get off the air Saturday.
Randy Lemmon's GardenLine is heard 6-10 a.m. Saturdays and Sundays,
exclusively on NewsRadio 740 KTRH.
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