Express-News Weekly Article
Saturday, April 22, 2006
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
 “Weeds and their Control”  

            Last year at this time our lawns were loaded with weeds because we had considerable rain over the winter.  This year, however, the lawns are relatively empty of weeds.  What you may see on the lawn are declining winter grasses like rescue grass, rye grass and annual blue grass.  They form seed heads now, and decline with the heat.  The key to their control is to keep the lawn mowed, preferably before the seed heads mature.  There is no advantage in spraying a herbicide for these weeds.  They are dying anyway.

 

            Some folks look at the dying weed grasses and think they are part of the lawn, and in an attempt to renew them, they begin watering in earnest, and also fertilize the lawn.  The good news is that our regular St. Augustine, zoysia, and Bermuda grasses will benefit by the water and the fertilizer now.  The weather has been warm enough, long enough to support growth. 

 

            Bermuda grass makes a great lawn if it receives full sun and is mowed frequently.  Bermuda grass is also a major weed.  The grass is perennial and nearly invincible in terms of traffic and drought.  There is hope, however.  There are many herbicides that work well to kill Bermuda grass.  Contact herbicides like Roundup and Finale work very well if sprayed on Bermuda when it is growing vigorously.  Use these products to spray the weed when it is isolated.  Both products will kill other plants if it gets on their foliage or green stems.  The grass specific contact herbicides, however, can be sprayed on Bermuda grass that is growing in your flower gardens, ornamentals, and groundcovers.  Spray the Bermuda foliage, and within a few weeks the grass will die, including roots.  You can make straight lines between garden beds and lawn with the spray, and used every month it will keep Bermuda grass completely in check.  The spray will not hurt your roses, zinnias, Asiatic jasmine or other broadleaf plants even if the spray wets the leaves.  Products like Over the Top, Grass be Gone, Poast, Fusilade, and Vantage are easy to use, but you must follow the label instructions exactly as written.

 

            I have been asked about vinegar as a control for Bermuda grass.  Vinegar is effective in killing the tops of growing weeds, but does not kill the roots.  It works well for young annual weeds, but for perennials like Bermuda grass it is only as effective as mowing for control.  Remember, vinegar will also kill the foliage of your flowers and shrubs.

           

            If you listen to Gardening South Texas on KLUP radio you know that I occasionally recommend the herbicide Remedy for Tough Weeds such as hackberries along fencelines. It operates a lot like Roundup, but also has the capability of penetrating bark of woody weeds.  The chemical does not require a license to buy and use, but it is volatile and expensive.  Volatile means that it floats in the air and can damage plants downwind.  This characteristic can be partially controlled by using a carrier like linseed oil, but Remedy is not a product for casual use.  Read the instructions well before you purchase it.

 

            In your rose beds and shrub borders the best way to control hackberry, mulberry, ligustrums, and other pesky woody weeds is pull them when very young or cut them off at ground surface if they are too large to pull.  The cutting will have to be done every month for a while, but gradually they will decline and die. 

           

            Sandburs are a special problem in many landscapes.  Their control is not an easy process.

 

·      Apply a pre-emergent herbicide such as Amaze, XL, Balan, or Betasan sometime in March or April.  Follow the instructions closely.  If the product is applied haphazardly, you will be disappointed in the results.

 

·      Apply a second dose two months later.

 

Follow this procedure for two years running and you should win the battle with sandburs – at least until neighborhood pets track in some new burs to serve as seed.-