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Healthy turf defense against weeds
The Coast Gardener Newspaper and Web Column - February 2, 2002

What exactly is your definition of a weed? I'm sure I would get many different answers to this question, and some of the answers might cause some gardeners' blood pressure to rise a bit. Just mentioning the word "dollar weed" evokes a sense of anger among many South Mississippians.

By definition, a weed is any plant out of place. Most of the time, however, we associate the term weed with unsightly, sometimes aggressive plants that are unattractive in the landscape. Sometimes they may even compete with desirable plants such as vegetables and turf.

While I can't get into specific control recommendations for individual weeds, I will try and give a general weed control strategy for your lawn. Ultimately, the best defense against weeds is a healthy, vigorously growing turf. This helps to minimize bare spots and keep the weeds shaded and choked out.

Always follow an approved liming, fertilization, and mowing program for your specific turf. A soil test is the best way to know exactly what lime and fertilizer, if any, you should add to your lawn. Too much of a good thing is as bad as not fertilizing at all. Don't guess&emdash;soil test!

If your lawn is still fighting a losing battle, always identify the problem weeds. Remember, it is nearly impossible, especially in the hot, humid South, to have completely weed-free lawns. If it's green, mow it! Sometimes this seems like the easiest and most logical approach. Other times, however, the weeds are too aggressive and need to be controlled.

What times of the year are your weed problems the worst? Do you have a problem with winter weeds or summer weeds? What is the name of your weed? Is it a broadleaf weed, grassy weed, or sedge? These are a few questions that need to be answered before trying to manage them. Notice I didn't say eliminate them.

Chemical control is sometimes required when the weed situation gets out of hand. Selective herbicides kill some plants but not others. The undesirable plants are killed, but the turf grass is not harmed. Moreover, nonselective herbicides such as glyphosate kill everything. Glyphosate is the active ingredient in products such as Roundup‚.

Preemergence herbicides are applied to the soil surface or turf canopy before the weeds come up. If you fail to treat weeds in the way, you are taking the defensive against weeds for the rest of the year. These herbicides are applied in late winter to control summer weeds that will sprout during this time. Next year's winter weeds are controlled by an application of a preemergence herbicide again in late summer.

Postemergence herbicides are those that are applied while the weeds are actively growing. These herbicides will help to clean up what the preemergence herbicides missed. Weeds are best controlled in this manner when they are less than three inches tall, and several applications are usually necessary throughout the season.

Next week, I will further explain the methods of herbicide application and offer suggestions to choosing the right ones for your lawn. Remember, however, that a relatively weed free lawn starts with a healthy turf.

These archived gardening columns were written by Chance McDavid, former Harrison County Extension Agent.