Native to: Tropical and warm temperate regions
Type of weed: Grassy weed
GreenGrass treats with: Pre-emergents in the spring, post-emergents in the summer
Over the counter: Product containing Pendimethalin, OR dithiopyr OR benefin and trifluralin. Always read the product label to see what it controls, what you can put it on, and how to apply it.
Crabgrass is an invasive grassy weed that can take over a lawn, especially in thin, stressed turf areas. The fact that your best defense against weeds is a thick, healthy turf is never truer than it is with grassy weeds like crabgrass. Crabgrass is an annual weed that reseeds itself every year and usually appears in April, dependent on weather.
Pre-emergents in the early spring are the absolute best way to control crabgrass. Once the weed germinates and becomes established, it's very difficult to control, and the material used to kill it will temporarily yellow surrounding turf. If you wait until summer to think about weed control, or if you start a lawn care program in the summer, you'll have a very tough time getting the crabgrass (or other difficult grassy weeds) under control.
Even if you did apply pre-emergents in the spring, they will break down sooner or later, usually in late summer, depending on the weather conditions. Again, keeping your turf thick and healthy is the best way to keep out unwanted grasses. Many people give up on watering in late summer, especially in drought conditions. It's hot, and they don't want to mow anyway, and they're tired of the high water bill. If you choose to do this, just bear in mind that dormant turf grass is an invitation for weeds to come in.
Crabgrass trivia: It is believed that crabgrass was cultivated as early as the Stone Age, and by 2700 B.C., it was an important grain crop in China. Crabgrass is a traditional food in India and Africa, but was introduced into the U.S. in the mid-1800's as a forage crop for livestock. When the Department of Agriculture was formed, crabgrass became a main agricultural crop....that is, until everyone realized that corn and wheat brought in a lot more money! Still, crabgrass is grown as a staple crop in some countries today, like Africa, where it can produce 17 tons per acre. The seeds are ground for flour, or toasted for hot cereal like oatmeal, or even fermented to make beer!