County Gardeners Extension Express

Are Weeds Killing My Lawn?

The answer to the question above is no! Although, I must admit, I’ve gotten that question many times, one must understand that weed growth is a result of a bigger problem, an unhealthy lawn, not a cause of decline. Likewise, killing the weeds will not cause the grass to grow. Weeds and turf are in competition, and the strong will survive.

There are many causes of turf decline: too much nitrogen on Centipede and St. Augustine, overwatering or underwatering, stresses or damage from drought, poor drainage, disease, insects, heat or cold, shade, lack of nutrients, or an accidental misuse of a pesticide. But, most issues begin with over management, applying too much of something for lawn improvement when it doesn’t want or need anything at all. Proper management, after all, is turf-type specific. Centipede needs less management followed by St. Augustine, Zoysia, and then Bermuda.

If you suspect a nutrition issue, a soil test will provide the needed information. Your local Extension office can assist, if needed. If you question shade being the problem, go outside and look up. St. Augustine followed by Zoysia are the two most shade-tolerant grasses but not for full shade. Centipede has some shade-tolerance and Bermuda has none. Keep in mind, trees grow and so do their canopies which produces more shade over time.

We cannot control the amount of rainfall we receive but we can control the amount of irrigation we apply. During early morning hours,1 inch total per week or 0.5 inch two times per week is a good rule of thumb during dry periods. You can increase it to 1.5 inches during periods of extreme heat. Measure the output using a flat-bottom container, such as a tuna can, by measuring the amount of water in the container after a run cycle. Adjust the output time as needed and correct areas with poor drainage, if possible. Turn your irrigation off when receiving periodic rainfall. Your lawn doesn’t have to be watered every week, rainfall or not.

Pesticides are handy tools for keeping weeds, insects, and diseases at bay. They must be used according to the label to be effective and not damage your turf. Many weed control products are ok to use on some grass type but not others. Application rates may also change depending on turf type. Timing of application is also important. There are many suggestions on a pesticide label to help prevent turf and/or environmental damage. Read and follow them!

The presence of a great number of weeds is a sign the turfgrass is not thriving. There are many stresses that affect desirable turf such as those mentioned above, including over-management. After the turfgrass is gone, weeds move in due to more available sunlight. For more information refer to Publication 1322, Establish and Manage Your Home Lawn.

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