Archive for Thursday, April 6, 2006

Put the ‘free’ back into ‘weed-free’ lawns

April 6, 2006

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Most home lawns in our area are either cool-season grasses, warm-season grasses or a combination of both. Unfortunately, across the middle United States, we live in a transition zone. The cool-season grasses fescue, rye and bluegrass grow better north of here during the hot summer months. And the warm season grasses zoysia and Bermuda survive winters better the farther south you go. Oftentimes turf managers refer to the transition zone as the "crabgrass belt" - appropriately named because in some years crabgrass is all that grows well. So, if you are one of the many who find themselves mowing crabgrass more than fescue, here are some tips to help put the "free" back into "weed-free" lawn:

Although crabgrass can be found in just about every corner of the county, it is not native to this area. It was introduced in 1849 as a low-maintenance, low-cost animal feed. Settlers quickly learned how easy it was to grow. As a result, it now can be found growing in all 48 continental states. With this in mind, crabgrass eradication takes more than just chemicals. As invasive as it may be, crabgrass is not the cause of an unhealthy lawn - it is the result.

As the desirable grass dies out, crabgrass moves in. The best way to stop the invasion is to focus on the care of the desirable grass. Start the defensive by raising the mowing height. The higher the mower is set, the less sunlight reaches the soil, resulting in fewer weed seeds sprouting. Next, water as needed. Too much or too little water weakens the roots of grass and causes the stand to be sickly and sparse. Finally, fertilize in May, September and November. Applying too much fertilizer or applying it at the wrong time may only give the crabgrass more energy for growth and development.

The second line of defense is to apply pre-emergent herbicides. Pre-emergent herbicides are chemicals that prevent the plants from emerging. However, many folks have been led to believe that they keep the seed from germinating. Not so. Rather, the germinating seed encounters the herbicide in the soil and is killed as it tries to emerge. This scenario is actually more beneficial than if these herbicides prevented germination because a germinated seed is no longer viable and can not cause future problems.

In most cases, pre-emergent herbicides need to be applied before weed seeds begin to germinate and grow. This is usually when the soil temperature reaches 55 degrees. A better method of gauging the time of application is when the redbud and forsythia are in full bloom. With that said, now is the time to fire up the fertilizer spreader.

Barricade and Dimension are two commonly available crabgrass preventers. Barricade can be applied in the fall for crabgrass control the following season. It should be fall-applied when it is combined with a fertilizer carrier. Dimension is unique in that it can be applied after the crabgrass has germinated, as long as the plants are still small.

And for all you procrastinators, Dimension can be applied through early May with good results. Both products have longer residual activity than other crabgrass preventers. This means two things: You can apply them early in the spring, and you will not have to make a second application like with other products. Other chemicals you may wish to use are Haults, Surflan and Team. When using the latter three chemicals, purchase them without a fertilizer carrier and make a second application eight to 10 weeks from now. With all five chemicals, water well to activate them and begin the prevention process.

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