For starters, crabgrass is a nasty little weed once you get it in your lawn. No, not as nasty as the guy shown to the right. For most people, they are plagued by its annual appearance and are unsure as to how to get rid of it. The most common crabgrass you will likely encounter are: Large Crabgrass (Digitaria sanquinalis) or Smooth Crabgrass (Digitaria ischaemum).
Both of these can thrive in areas that most grasses do not fair very well. Once established, they can be difficult to get rid of. A single crabgrass plant can produce as many as 150,000 seeds in a single season!
So, how do we kill it or keep it out? The first trick is hopefully the easiest and makes the most sense. Start with a healthy, lush lawn. Dense lawns that are properly fertilized, watered and mowed at the correct height should be your first defense. How does this work? The lawn acts as a shade, and blocks out the sun for the newly emerging crabgrass seedlings.
If some of them do manage to break through, do not worry. You still have options. Look no further than good old fashioned manual labor! As the crabgrass gets bigger, pick it out with a garden spade or by hand. If there is simply too much to pull out, you may want to consider using a postemergent herbicide. Be careful to read all the instructions on the label and follow them carefully. It may take several applications depending on how big the crabgrass has become.
So you didn’t catch the crabgrass early enough. Don’t give up hope. It will die off with the coming winter. Next year you may consider a pre-emergent herbicide. Wait too long and you may face the same problem. All those seeds left behind lay dormant in the soil until the soil warms to 50-55 degrees. Depending on where you live, this is typically in the first part of March or April. A pre-emergent herbicide forms a chemical barrier at the soil surface. Any seedlings trying to poke through are killed.
Simple enough? Make sure to not to do any soil cultivation or aeration until the fall. This will break apart that barrier you put down and make your efforts useless. Now for aerification… that is a different topic to be discussed later on.