KENNEWICK -- I recently heard a group of gardeners talking about the problem of controlling Bermudagrass in landscape beds.
Calling it a problem is an understatement. Control of Bermudagrass is a colossal challenge and can't be achieved easily. Before we talk about control, let's talk a little about this pernicious grassy invader.
Bermudagrass didn't come from Bermuda. This low-growing, blue-green perennial grass was introduced to this country from southeast Africa in 1751, and has been used as a forage grass for livestock and as a lawn grass in the warmer regions of the country, where cool-season grasses are difficult to grow. In fact, there are cultivated varieties of Bermudagrass that don't produce seed, developed for use in these regions.
In this area, few people purposely plant Bermudagrass lawns, but end up with lawns and landscape beds invaded by this aggressive warm-season grass. Bermudagrass can propagate itself from plentiful seed that develops in late summer. Seeds stay viable in the soil for at least two years.
Bermudagrass also spreads by tough, wiry rhizomes (rootlike stems in the soil) and stolons (trailing above-ground stems that can root at base of every leaf or node).
Pulling or simple cultivation are not effective ways to control Bermudagrass because pieces of rhizomes or stolons left behind can grow into new plants. However, a persistent program of cultivation and withholding water over an entire season can end in success, if there are no desirable plants in the bed that will suffer from a lack of water and regular cultivation.
Many gardeners use glyphosate (such as Roundup or other brand names) in their attempts to control Bermudagrass. To be effective, glyphosate should be applied when the grass is actively growing in mid-summer. Two to four applications timed three to four weeks apart may be needed for satisfactory control of any regrowth. Perseverance is essential.
The problem with using glyphosate in landscape beds near established trees, shrubs and perennials is that it's "nonselective." If glyphosate is applied to green leaves, stems or even thin young bark, it can enter these desirable plants and cause damage. I have had several plants brought in to me this year that were exposed to glyphosate last summer or fall and were showing signs of herbicide injury this spring. Symptoms include stunted, distorted and narrowed yellowing leaves along with dieback of growth. To avoid this problem, many gardeners will use a shield of cardboard between their desirable plants and the Bermuda grass when applying glyphosate.
Some gardeners have discovered that there are "selective' herbicides that will kill perennial grasses, including Bermudagrass, but will not harm most nongrasses including trees, shrubs, roses and perennial flowers to which they are applied. The two selective grass herbicides available to home gardeners are sethoxydim (Monterey Grass Getter) and fluazifop (Ortho Grass B-Gone). They work best in spring, when the Bermudagrass runners are 4 to 6 inches long and not drought stressed. Retreatment will usually be necessary and should be done when the regrowth reaches 6 inches again throughout the season.
Any of these herbicides are not a one-time "silver bullet" for control of Bermudagrass in landscape beds. Tenacity in using the nonselective glypho-sate or the selective grass herbicides will be needed.
Garden note: Many gardeners now have ornamental grasses in their landscape beds that can be damaged if exposed to these herbicides. Before using any of these products, read and follow the label directions.
* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension.