Even though crabgrass is invasive, it's not actually competitive. That means it won't push thick, lush, healthy grass out of the way. But if you allow your lawn to become weak and unhealthy, crabgrass is standing by to take over.
Crabgrass is a summer annual, meaning that in most climates it grows one year, produces seeds, and then dies off. The next year, the seeds sprout and the cycle continues. In temperate climates, the crabgrass will grow two years. It also spreads by putting out runners, which sprout roots where they touch the ground.
To prevent those seeds from germinating, experts at Purdue University suggest keeping a grass lawn healthy, thick and lush [source: Purdue]. That means watering deeply and infrequently, rather than sprinkling often, which produces shallow roots vulnerable to crabgrass infestation. Also, a healthy lawn should be mowed no shorter than 2 or 3 inches (5 to 8 centimeters). Shorter than that gives crabgrass an opportunity to move in and make itself at home.
You can also use chemicals to keep crabgrass seeds from sprouting. Those are called pre-emergent herbicides. Once the seeds have sprouted, your best option is to pull the crabgrass out by hand.
Because there are 235 species of crabgrass and it grows in all 48 continental states of the United States, it's probably unrealistic to think the crabgrass could ever be eradicated from one's life. But knowing how delicious it is to cows and horses might make it seem a little less vile. And the next time you dine on "grass-fed beef," consider that the grass may be a little crabby.
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