Crabgrass is a type of annual grass which appears in the warm season, and is native to Europe, although it has colonized much of North America as well, to the dismay of many gardeners. The stubborn rooting grass can be difficult to eradicate when it colonizes, and it tends to overwhelm native species with an aggressive seeding pattern and rapid growth habit. As a result, most gardeners try to prevent crabgrass from emerging in their gardens, and take serious steps to eradicate it when it does.

Crabgrass can refer to several grasses, all of which are in the genus Digitaria. The two most common problem species are Digitaria sanguinalis and Digitaria ischaemum. Both have high growing branching stems, although they can also adapt to live close to the earth in mats. These mats will spread and put out roots within a season. If allowed to flourish, crabgrass tends to choke out the grasses surrounding it, and will form depressions in a lawn which are reseeded with crabgrass seeds, allowing the grass to spread even further in the next season, especially if given ample water.

A number of steps can be taken to eliminate crabgrass, although constant vigilance is required. The first is to grow and maintain a healthy lawn which does not allow crabgrass to take root. Plan on seeting, fertilizing, and watering in the early spring, before crabgrass emerges, so that your lawn can get a head start. Seed densely to create a thick mat of grasses to keep crabgrass from getting a foothold, and water deeply and infrequently. Also keep the turf relatively high when you mow, as a lawn which hovers around three inches (7.6 centimeters) high will shade the crabgrass seeds, preventing them from sprouting.

When individual outbreaks of crabgrass occur, make sure to remove each one by hand, pulling up the entire root system. Some gardeners use herbicides to control crabgrass, applying preemergent herbicides before crabgrass appears, or control herbicides when it does pop up. The use of herbicides should only be undertaken as a last resort, however, as it can have an impact on the health of the rest of the garden, along with pets and children. Application of vinegar may also help, but be prepared to kill the entire section of the lawn to which the vinegar is applied, and reseed or sod quickly before crabgrass can root again.