Crabgrass is an annual that germinates in lawns when the soil temperatures are approximately 60 degrees Fahrenheit for three to five days. Crabgrass flowers and sets seed in July. It dies at the first frost. Crabgrass has evolved to reproduce at a fast rate. It grows in unhealthy lawns (lawn affected by drought and water restrictions) and lawns that have not been taken care of (improper fertilization and watering).
When you first see signs of crabgrass, kill the plants before they have time to flower and seed. New plants start any time during the growing season, so always be on the lookout for crabgrass. Pulling the plant and root system out as you see it prevents it from seeding. Use pre-emergent herbicides to control crabgrass before it germinates. The type you use depends on the type of grass in your lawn. Check with your local nursery for the proper pre-emergent herbicide for your lawn. Using a pre-emergent herbicide too early might allow crabgrass to grow during the summer. If it is applied too late, the crabgrass is already present.
Mow the grass often: at least twice per week in the spring and every other week during the summer. Mow the grass to a height of no less than 2 ½ inches. If you mow short, more sun reaches the soil, which warms the soil to the temperature needed to germinate crabgrass.
Mulching the soil once the crabgrass has been removed helps to keep missed root from taking seed and putting out new patches of crabgrass. Using compost not only helps keep the crabgrass at bay, but also provides nutrients for your lawn.
Soaking the area you are weeding helps loosen the soil, so that the crabgrass is easily pulled. Get the entire root, if possible, as the crabgrass will grow from pieces of root left in the ground. Once the crabgrass is removed, water the lawn with at least an inch of water each week. Watering deeply encourages root growth of the wanted lawn grasses, which in turn, encourages a healthy lawn. Healthy lawns have the ability to "push" crabgrass out of the lawn.