I saw a couple of lawns with a lot of crabgrass last summer. Generally, crabgrass thrives in lawns that are cut short and in drier areas near pavement. Fortunately, crabgrass has not been an issue in my lawn at home. Crabgrass is an annual, weedy, warm-season grass that prefers the hot and dry summer weather over the cool spring and fall temperatures that bluegrass prefers. It can blend into your lawn during the summer if you do not pay close attention. When you look closely, crabgrass can be identified by its wide leaf blade and light green color. It is easy to recognize when it grows in severely stressed areas, like along a driveway where the soil has been compacted from vehicle traffic. Thin areas in the lawn provide an opportunity for crabgrass and other weeds to move in. During the summer, this low-growing weed can also be identified by its seed spike resembling a turkey foot. The seeds turn a maroon color when temperatures begin to cool down in fall. Freezing temperatures kill this weed, resulting in patches of brown throughout your green lawn in fall.
The best way to prevent crabgrass is to maintain a healthy lawn that is thick and outcompetes crabgrass. Mow your lawn at 3 to 3 1/2 inches to promote a deep root system. This enables the lawn to better withstand stress and remain dense to help shade out weeds like crabgrass. I consider my home lawn low maintenance, and mowing high has worked well to exclude crabgrass. Thin areas like those in your lawn allow light to penetrate to the soil, which gives crabgrass seed as well as other weed seeds an opportunity to germinate. Light, frequent watering also favors the development of crabgrass.
If the infestation of crabgrass in your lawn last year was significant, you may need to use a pre-emergent herbicide now. These work to prevent crabgrass seed from germinating. Crabgrass preventer products must be applied before crabgrass begins to germinate after soil temperatures reach 55 degrees Fahrenheit for several days in a row. Germination timing can vary from year to year due to the weather. In a typical spring, apply the herbicide in early to mid-April. You may need to adjust timing if it is an exceptionally warm or cold spring. Most crabgrass preventers last for around 60 days, so you do not want to apply them too early in the season. They work by forming a chemical barrier that prevents seeds from germinating. Crabgrass generally germinates when redbud trees bloom, so apply crabgrass control about two weeks before they flower. It is important to read the instructions on any chemical products you choose to use.
There is no need to use a crabgrass preventer if you did not have more significant problems with crabgrass. The herbicide will also prevent some other annual weed species from germinating as well as grass seed, so don’t seed your lawn for at least two months after applying it. You should not do any raking, power raking or core aerating after you have applied crabgrass preventer to avoid breaking the chemical barrier formed by the crabgrass preventer.
