Crabgrass is a weedy grass that is quite common all throughout the United States. It is an annual plant that germinates from seed, grows, produces seeds and then dies off. This results in unsightly spots in your lawn, where the dying crabgrass leaves bare soil behind, which can make the lawn vulnerable to a further invasion by other weeds. Familiarizing yourself with methods to rid your lawn of crabgrass can greatly help you enhance its overall health and visual appeal.
Use a pre-emergence herbicide to kill off the seeds before they have a chance to begin germinating. For maximum effectiveness, you need to time your application of the herbicide to be in the soil two to three weeks before germination actually starts. As a general rule of thumb, when soil temperatures reach 59 to 65 degrees Fahrenheit, it is time to introduce the herbicide. A common method of application includes the use of a hand spreader. Do not rely on pre-emergent herbicides if you are also reseeding areas of your lawn; the substance will kill off newly germinating desirable grass seeds as well.
Corn Gluten Meal
Corn gluten meal is a by-product of wet-milling. If you spread it onto your lawn in spring and later on in the summer, it greatly inhibits crabgrass' ability to grow seedlings with deep roots. The heat of the summer dries out the seedlings that could not properly take root. You may find that this method is not completely effective. Since corn gluten meal also contains nitrogen, the weeds that do survive actually get fertilized and grow even stronger. Nevertheless, if you prefer an alternative to commercial herbicides, corn gluten meal offers an environmentally friendly option.
When crabgrass does establish itself in your lawn, consider spot treating it with a non-selective herbicide. Good choices are Round-Up and similar products. Opt for a wind free day and follow the instructions on the product package. While it is true that these herbicides will kill desired grass in addition to crabgrass, the careful application of non-selective herbicides greatly lessens the presence of crabgrass seeds for the next growing season.
Increase the overall health of your lawn grass. This makes it harder for crabgrass to invade. Mow high in the summer---between 2.5 and 3 inches---to limit weed germination. Anthony J. Koski, turf grass specialist and professor from the Colorado State University Extension, advises that crabgrass is much more vigorous and frequent in lawns mowed lower than 2 inches. Continue grassroots strengthening by fertilizing for your specific lawn grass type and irrigating to strengthen established roots rather than surface germinating seeds.