For Release October 15, 2002

Fall Is the Time to Control Many Lawn Weeds

by Chuck Otte, Geary County Extension Agent

The rains that we had the first week of October did a lot of good things for us. I noticed one of those good things as I was walking across lawns last week. In between the grass plants were lots of little green seedlings. These little seedlings have such wonderful names as henbit, dandelion, chickweed and speedwell.

These tiny young plants will grow for the coming weeks until the ground becomes cold enough that they go dormant. They don’t look like much now and won’t look like much even by the time they go dormant in November or early December. But along about late February or March they will start growing with a vengeance. And then, before you know it, they are covering parts of your lawn with yellow, white, purple and blue flowers.

Once they start blooming next spring, it is all over. Even if you spray them, they will still make seed before they die. In fact, once they start blooming, they are on the downhill side of their life cycle. By the time spring has become summer, most of these plants will be dead and seeds sown for another generation. These plants are called biennials or winter annuals, with the exception of dandelions which are short lived perennials. They start their life cycle in the fall. They go dormant in the winter and finish growing in the late winter and spring. Think of them as the winter wheat of the weed kingdom.

The time to control these weeds in your lawn, is now. Right now, these plants are small. They have little bitty root systems but they are concentrating on building up a big healthy root system. A herbicide applied at this time of year is going to be very quickly taken up by the plant and will be very efficient at controlling these tiny weed seedlings.

Spraying in the fall has several other benefits. The herbicides that we use to control these weeds are potentially toxic to any broadleaf plant in your yard. These herbicides can curl the leaves of tomatoes, grapes, walnuts and redbuds just from the vapors that come off the chemicals when they are applied on warm days in the spring. But it is fall now. The leaves are turning color and falling off the plants. With scattered frost over the weekend, many plants have, or are, shutting down. A little drift, while never desirable, is going to have much less effect. In the spring, all those plants have young tender leaves that are very sensitive to the vapors.

Most all of these fall lawn weed killers have to come in contact with the leaves of the weeds. Most of these weeds have just sprouted in the last ten days. If you applied a weed and feed product in early September, you may very well have missed all those seedlings that are just now sprouting. Wait a couple more weeks and see if the young weeds are wilting and dying. If not then a second application may be necessary. The good news is that we probably have another good month of being able to treat these weeds if a re-treatment is necessary.

However, keep in mind that weeds are not the real problem, but merely a symptom. The real problem is that your lawn is not thick enough and tall enough to keep the ground all covered. If it was, you would have very few weeds and a herbicide treatment wouldn’t be necessary. So take advantage of the time we have left this fall to finish overseeding thin spots, fertilizing your lawn to make it more aggressive and raising your mower’s cutting height. An aggressive lawn is the best weed control you can have!


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