Every year about this time lawn and garden supply stores will put up the signs saying it is now time to control grassburrs. Anyone with a grassburr problem certainly wants to do everything that they can to control this problem grass but it sure seems early to control them when the lawn hasn’t even started to green up.
The real problem with controlling grassburrs is that we want to get them before they put out those pesky seedheads. This particular weed is in the monocot or grass family and it is one of the warm season grasses. It functions like most other annual grasses in that it produces seed, that seed lays dormant on the soil until the right combination of light and moisture occur to germinate. It takes fairly warm air temperatures along with warm soil temperature to get grassburr seed to germinate since it is a warm season grass. The problem for the homeowner is knowing when all the right conditions will happen so that you can apply a PREEMERGE HERBICIDE before they do happen.
Herbicide is simply a herb killer meaning that it will kill plants. A preemerge herbicide is applied before the plant emerges from the soil and so it kills the plant before it has a chance to really grow. In order for preemerges to work they must be applied before all the conditions are right to germinate the seed. Some of these warm days it certainly feels like spring has sprung. It may feel warm but the soil is still cold and so the seeds wont germinate. In a few weeks though we will have seen our last frost and the days and nights will start warming quickly and then grassburrs will come alive. Because we don’t know for certain when all this will happen we apply preemerges early, usually the first two weeks in March to be ahead of the warm weather. The problem with applying them this early is that they don’t last long enough in the season. Many homeowners have complained that preemerges don’t work when what really happened is that the homeowner didn’t make a second application later in the season. These products are good but they are not so good as to last forever.
One question I also get asked a lot about is, “does corn gluten meal work?” Well for good information I like to go to the source so I looked up Dr. Nick Christians’ website in the Department of Horticulture, Iowa State University. Dr. Christians did the initial research on corn gluten meal as a preemerge in turf and he holds the U.S. government patent for its use as a preemerge. This is what he says, “Consumer acceptance of corn gluten meal as a natural herbicide has been good in the turf market. To date, most of its use has been on home lawns, but professional use has been increasing. Like any natural product, it has some disadvantages. You should time its application in the 4- to 6-week period before target-weed germination, which means that you must have a good knowledge of weeds and their life cycles. Use in the first year generally results in a reduction of 50 to 60 percent of the target weeds and 2 to 3 years are necessary to match the results of synthetic pre-emergence herbicides. The product is also more expensive than synthetic weed-and-feed materials. The target market for the product is the growing number of people who refuse to use synthetic pesticides and fertilizers but still want to do something about their weed problem and are willing to pay the higher price.” He recommends 20#’s per 1000 square feet of lawn. The price of this is around $21.90 per 50# bag or $8.76 per 1000 square feet of lawn.
To sum up this discussion you first need to get everything ready and put out a preemerge. You need to buy a good product that is okay for your grass and of course has grassburr control on the label and hopefully how long they will be controlled. Here is a list of products that Jim McAfee, Extension Turfgrass Specialist put together (Click Here for list of Pre-emerge Products) When you apply the product it is very good to go in two directions for complete coverage. Just split the material in half and go one way then go the opposite direction with the other half. The lastly make sure you put on the second application based on what the label says. Satisfaction guaranteed!