Weed Problems Common In Poorly Managed Lawns Says LSU AgCenter Agronomist

Ronald Strahan  |  4/30/2005 1:02:34 AM

Henbit is one of many annual spring weeds that actually started its life cycle the previous fall. Learn how to prevent the cycle from starting over this year in this article.

News You Can Use For May 2005

Weeds are unwanted plants that compete with your lawn for water, nutrients and light. Practically every lawn has lingering winter weed problems during spring, according to LSU AgCenter agronomist Dr. Ronald Strahan.

Winter weeds that started emerging in early October are now flowering and completing their life cycle. With a few exceptions, most of these weeds are winter annuals.

"The good news is, as our daytime temperatures approach the 80s, winter annuals like chickweed, henbit, annual bluegrass and creeping bedstraw (the one that sticks to your clothes) die rapidly," Strahan says, adding, "The bad news is these plants will not die before they produce thousands of seed for next winter’s crop."

The agronomist explains that each year, winter annuals deposit more seed to their soil seed bank, ensuring that your weedy mess will return next spring.

So what can a homeowner do?

"I hate to tell you this, but if your lawn is a weedy mess, it’s usually caused by mistakes in turf management," Strahan says, explaining, "In other words, you don’t see a lot of weed problems in lawns that are fertilized at the proper time with right amount of fertilizer and mowed correctly (yes, there is a correct way to mow)."

The agronomist asserts, "I am convinced that we are our lawn’s worst enemy. We mow too low and rarely or improperly fertilize."

Believe it or not, Strahan says, you can significantly reduce your winter weed problems next spring by adopting simple management practices for this growing season. Fertilizing on schedule and mowing your lawn at the correct height contribute more to weed control than any weed killer. Weeds don’t like competition any more than your lawn does.

"What you are actually accomplishing with good lawn management is making your lawn thicker and healthier and more competitive with weeds," the agronomist says.

The three most common lawns in Louisiana are St. Augustinegrass, bermudagrass and centipedegrass. Unfortunately, all three of these lawns are susceptible to weed problems if they do not receive good care.

St. Augustinegrass is a shade tolerant, dark green, coarse-textured turf that requires a good bit of maintenance. The biggest problem between homeowners and St. Augustinegrass is mowing height. If you mow St. Augustinegrass too short, it will thin out, and the weeds will simply take over. Therefore, raise your mowing deck to the highest or next highest setting and maintain this lawn around 3 inches.

St. Augustinegrass likes to be fertilized at least three or four times during the growing season at a pound of actual nitrogen per application, such as 12 pounds of 8-8-8 fertilizer per 1,000 square feet. Your soil pH needs to be near neutral, or 7, for optimal growth.

Increasing the mowing height and fertilizing will create a lush green carpet that out-competes weeds during the summer. During the winter, the thick dormant lawn acts almost like mulch that will work as a barrier to reduce winter weed infestations.

Bermudagrass is one of the most common lawns of north Louisiana. It is a very aggressive, wiry, narrow-leafed grass known for its wear tolerance. Bermudagrass will not tolerate scalping with a lawn mower, but it can be mowed lower than most other lawns. Maintain bermudagrass at 1 to 1 1/2 inches.

Bermudagrass comes in several different types. Improved seeded and hybrid bermudagrass may require fertilizing every month during the spring and summer for optimal performance. Common bermudagrass needs to be fertilized at least three or four times during the growing season to reduce weed competition. Well-maintained bermudagrass has few weed problems in the summer or winter.

Centipedegrass is a slow-growing, pale green grass that has become our most popular turf in Louisiana over the past few years. It is often called "the carefree lawn of the South" or "the lazy man’s lawn." In other words, centipede requires very little maintenance, prefers acidic soil and has few pest problems. In fact, you can over-fertilize centipedegrass and cause serious problems.

Homeowners see centipede’s slow growth and natural pale green color and try to make the turf greener by fertilizing too much. In reality, centipedegrass should receive no more than 2 pounds of actual nitrogen per year. Fertilize only once or twice during the growing season. Maintain it at 2 inches tall. It will be slow to recover if it gets scalped by a mower. Also, the grass does not tolerate drought very well. During dry spells, weeds have the upper hand, so make sure to water centipedegrass sufficiently.

Even if your yard may look like a disaster now, lawns are so forgiving you can actually correct years of mismanagement in one growing season, according to Strahan. Begin by getting a good representative soil sample and dropping it off at your local county agent’s office for analysis. (Prices vary according to the extent of the analysis.) This measurement will give you your soil pH and an idea about any deficient nutrients.

For related topics, look for Gardening and Get It Growing links in the Feature section of the LSU AgCenter Web site: www.lsuagcenter.com. Additional yard and garden topics are available from an extension agent in your parish LSU AgCenter office.


On the Internet: LSU AgCenter: www.lsuagcenter.com/
On the Internet: www.louisianalawnandgarden.org
Source: Ron Strahan (225) 578-2392, or Rstrahan@agcenter.lsu.edu

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