Part Two: Managing Weeds In Warm Season Grasses

Weed control in warm season grasses begins with proper management practices.
These management practices include mowing height and frequency, watering rate and frequency, liming, core aeration to reduce soil compaction, de-thatching, and fertilizer analysis, rate and timing.
It is recommended that each warm season grass should be mowed so that no more than 1/3 of the blade is removed. Cutting off more than 1/3 of the leaf blade at one time can stop the roots from growing and would require more frequent watering during hot, dry summers.
By following the 1/3 rule, you produce smaller clippings that will decompose quicker by filtering down into the soil surface. Mowing at the proper height for the particular turfgrass will encourage a dense, healthy lawn.
Mowing heights may be raised slightly for turfgrass in partial shade. If the height of your grass becomes too tall between mowings, raise the mowing height and gradually reduce the height of the grass until the recommended height is reached.
See the table for the recommended mowing heights for warm season grasses:

Typically, lawns need 1 inch of water per week, either through rainfall or irrigation. A simple way to measure rainfall at your home is with a rain gauge.
One inch of irrigation water will wet the soil 6 inches deep and will encourage a healthy, extensive root system. In the sandy soil regions of the Pee Dee, irrigation may be required every 3 to 4 days during hot and dry periods.
Watering more frequently (more than 3 or more) times a week will keep the soil surface moist and will promote weed seed germination and will encourage a shallow root system for your grass.
Stretch the interval between waterings to as many days as possible to encourage the development of a deep root system.
The most beneficial time to water a lawn is in the early morning.
Water evaporation is minimized so more water is going to the grass and less to the atmosphere.
Early morning irrigation also helps decrease the development and spread of diseases. The grass blades dry off quickly and reduce the probability of fungus spores from germinating and infecting the leaf tissue.
The most efficient way to water a lawn is when the lawn begins to show signs of stress from lack of water.
There are several techniques to identify when your lawn may be stress due to lack of water. The color test is when your lawn a blueish-gray.
Another method to determine lack of water is by the footprint test.
Walk across your lawn late in the day and scan the lawn behind you to see if you see your footprints.
Low water levels in the plant tissue prevent the grass blades from springing back up. If you observe your grass wilting, rolling, or folding, that is the grass’ response to drying out and you should water your grass to prevent it from turning brown and becoming dormant.
Stay tuned for upcoming news articles for more information on best management practices on turfgrass and controlling weeds using herbicides.
For more information on types weeds in warm season lawns, please visit the HGIC website at hgic.clemson.edu. Tune in on Tuesday nights to watch “Making it Grow” at 7 p.m. on SCETV or mig.org.
E-mail Callen Outen at [email protected] or call at 843-627-7113.
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