Bermuda grass is a problem for all gardeners in the Houston area. The method by which it invades a garden makes Bermuda grass difficult to control.
First, it mixes in with the "good" plants. That makes the use of herbicides such as Roundup or Finale risky. This is especially true because Bermuda grass often grows "under" the canopy of good plants near their stems. It sends out runners from there. I use Roundup for everyday control of Bermuda grass, but I am careful to keep the Roundup off the green foliage of the plants I like.
A second problem involves the way Bermuda grass spreads. It grows by sending "runners" both above ground (stolons) and below ground (roots). Anyone who has tried to pull up Bermuda "by the roots" can attest to the extensive underground root system which makes it virtually impossible to eliminate this pest by "weeding."
Organic methods to remove it include tilling four to six inches deep and removing all roots or spraying with a soap based herbicide such as Safer Superfast brand Weed and Grass Killer. It will take three or more applications of the Safer product to kill the Bermuda. Patience is required.
Now there is a chemical solution which allows one to spray a chemical over most existing plants and kill only the Bermuda (and other thin bladed grasses such as St. Augustine). Wildseed Farms (800 848 0078) of Fredericksburg, Texas, sells Ornamec, a grass herbicide that will not hurt most plants but will kill Bermuda at the roots in about three weeks. Wildflower gardeners use it to kill Bermuda grass growing in the midst of their wildflowers "without injuring transplants, emerging wildflower seedlings or established plants in full bloom." Unfortunately, Ornamec does not kill nut grass. Also, Ornamec is not selective among grasses. That means you cannot use it to kill Bermuda growning in the midst of St. Augustine. Sorry.
The product literature lists scores of plants that Ornamec will not hurt. These plants include aloe vera, alyssum, bush lantana, chives, crepe myrtle, daylilly, hollyhock, hybrid tea roses, iris, ixora, japanese yew, jojoba, liriope, live oak, marigold, Mediterranean fan palm, morrow honeysuckle, olive tree, passion vine, pygmy date palm, red fountain grass, rose, rosemary, sago palm, sedum, Sweet William, sword fern, Texas privet, Texas sage, wax myrtle, weeping willow, and yucca.
The makers of Ornamec warn: "DO NOT APPLY TO ORNAMENTALS THAT MAY BE HARVESTED FOR FOOD WITHIN ONE YEAR AFTER APPLICATION."
The last time I ordered Ornamec it costs $19.99 for 20 ounces, which treats up to 5,000 square feet. Give it a try.