Question
I live in South Carolina and my back yard is covered with crabb grass.  I've had centipede grass in the front and back, but only the back yard became infested with this weed.  How do I kill it?  I've already been pulling them out, but there is too much.  Thank you.

Answer
Hi Debbie K.,

ABOUT a WEED CALLED 'CRABGRASS':

 "Crabgrass" is a common name for a plant usually better identified in the U.S. as a species of DIGITARIA. There are about 20 or so species and some people are actually using it as a ground-cover for shady areas; it will grow to give a grassy coverage where many turf-grasses will fail.  It is also now being included in commercial birds seed products which can be fine for the birds but a persistent source for the weed in residential areas.  Crabgrass is also a classic pasture grass for live-stock.   So there are some good qualities for this very common weed.

The seeds are medium-sized and can be carried some distance by the wind. If you live near pasture and wild areas,...you will have an eternal crabgrass invasion. Keeping it from making seeds within your perimeter is a primary control, especially if you live where cold weather kills it until the next spring spring.  It helps to have neighbors who also work to keep this weed in check.

 As almost all weeds can be divided into two main groups, namely, the Broad leaf versus the "grassy-type" weeds, Crabgrass is controlled by herbicides sold to use on GRASSY-TYPE WEEDS.  Any garden center or hardware store should have one or more popular brands you can try.  Look for the common and/or technical name on the product label to be sure the chemical targets 'Crabgrass,...Digitaria species'.  

 MSMA and DSMA are also excellent for killing crabgrass, but because these contain a salt of arsenic and may not be available in your county or state.  If these arsenic salts are sold in your town, they should not be used near water supplies, rivers or streams.  Most soils will have so much natural arsenic in it, but the EPA does not want any more than what exists naturally because Arsenic is very toxic to all living things in certain amounts.

 Most grassy weed-killers will also have some effect on your wanted lawn grass if these get sprayed in the herbicide using process, so you may want to use the chemical slightly diluted and in more treatment applications ...the effected plant slowly turns yellow, blanches and shrivels up while slightly dosed turf grasses just get a slight set-back, turn yellowish and, with proper doses of the chemical,...the turf-grasses should recuperate.

Information about turf-grasses affected by a grassy-type herbicide should be on the product label; you can also find out more about many lawn and garden chemicals by logging on to the manufacturers web-site.

 As state,...Crabgrass is an annual warm weather loving weed and if you can prevent it from producing and dispersing its tiny seeds you can do much to prevent its proliferating. Mow it low before it can send up its seed heads or manually pull it up, taking care to dispose of its seeds.  The plants die totally with the first frost and it all starts anew when warm weather returns.

If you live where night temperatures rarely drop below the mid-fifties,...you may have more of a problem with Crab-grass.  A pre-emergent herbicide is the remedy for this.


 Use a PRE-EMERGENT HERBICIDE regularly and especially in the early fall and mid winter and crabgrass and many other weeds will not even get started.  These herbicides prevent germination.  Some fertilizers are sold with "crabgrass preventer" supplements in them; these also may be pre-emergent herbicidal granules. You must read the label on granular products to be sure if or not there is a PRE-EMERGENT chemical in the bag, some products will state it is preventive, but the chemical is a granular version of a POST-EMERGENT chemical.  The PRE-EMERGENT chemicals are the more expensive  products, but are well worth the extra costs if you want a consistent weed-free lawn eventually.

Again, check the labels and take the time to read and learn about what you are using, to avoid problems,..and to know what to expect.

In summary, using Pre-emergent herbicides, and preventing the seed production/dispersal of this weed is the best way to remain crabgrass free for the long haul.
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