One of the worst weeds we have in Louisiana turfgrass is Virginia buttonweed. The spread of this weed has increased tremendously over the past few years.
Virginia buttonweed (Diodia virginiana) is a prostrate-growing, mat-forming summer perennial with radially spreading branches. It is easily identified by its opposite leaf arrangements and its four, white star-shaped petals, which sometimes can also have pink streaks through the center of two of the sepals. Virginia buttonweed typically thrives in moist-to-wet soils in the lawn.
This weed gets its name from the seed capsules that resemble buttons that hang on the underside of the stems. Every seed capsule contains two seeds and has close to a 100 percent germination rate. Virginia buttonweed can reproduce by seeds, roots and stem fragments. The combination of these characteristics allows this weed to become the number one weed problem in Southern turfgrass.
This weed will continue to thrive in the lawn even while being mowed at a half inch. If the lawn is being mowed at the appropriate height, 1 to 3 inches depending on variety, then the weed will continue to thrive, set flowers, drop seed and reproduce. Unlike other broadleaf weeds in the lawn, mowing will not inhibit this process.
If you had Virginia buttonweed last year in your lawn, you can expect to see the mother plant re-emerging from the soil and the seeds of the mother plant germinating this month. Chemical control options for Virginia buttonweed include Celsius, Metsulfuron (MSM, Top Shot, or Mansion) Weed Free Zone or Weed-B-Gon. Repeated applications of these herbicides suppressed buttonweed in LSU AgCenter trials. Celsius and Metsulfuron are safe for all Southern turf, except bahiagrass.
Top Shot may be more widely available at your local nurseries and garden centers. Weed-B-Gon and Weed Free Zone are not quite as effective as Celsius and Metsulfuron. But with repeated applications, you will begin to see some suppression of Virginia buttonweed in your turf. Do keep in mind that St. Augustine and centipede grasses can become severely injured by the herbicides Weed Free Zone and Weed-B-Gon if they are applied when temperatures are above 90 degrees. Always be sure to read and follow labeled directions of all pesticides.