Crabgrass is also known as hairy crabgrass, finger grass, crow foot, purple crabgrass and Polish millet. It is native to Europe or Eurasia and was brought to the United States in 1849 as a patented forage crop for livestock. It can now be found in all cultivated and non-cultivated locations as a wild plant. There are two common varieties, large crabgrass (Digitaria sanguinalis) and small, smooth crabgrass (Digitaria ischaemum).
Crabgrass is an annual plant that grows as a perennial in temperate climates. It reproduces by seeds and extends tillers which branch laterally. Each plant can produce 150 to 700 tillers and 150,000 seeds.Seed production adapts to mower height and will continue to reproduce at 1/2 inch. Crabgrass seeds germinate when the soil is 60 degrees Fahrenheit for three to five consecutive days, from spring to fall.
Crabgrass is coarse with yellowish-green leaves that are conspicuous in finely textured lawn turf. Once established, crabgrass tolerates heat and drought conditions. It spreads by tillers easily into unwanted areas such as flower beds and vegetable gardens. Roots develop from node points. Plants that develop early in the spring are larger and more competitive than crabgrass that germinates in mid-season.
Crabgrass is a shallow rooted plant that is easily pulled up by hand. Its growth is discouraged by infrequent, deep watering. According to the Purdue University Extension website, "The most effective way to control crabgrass is to create a dense, healthy turf." Crabgrass cannot compete successfully with strong surrounding grass plants. Fertilization, mowing and irrigation help maintain healthy turf.
Crabgrass spray such as Weed-B-Gone and Roundup are non-selective herbicides that kill surrounding plants if wind or water carry it. Weed-B-Gone crabgrass spray has a class-3 toxicity rating with the Environmental Protection Agency, which is "slightly toxic" to eyes and skin. Roundup also has a 3-caution rating but has recently come under scrutiny for its inert ingredients, which have been shown to distort human cell reproduction.
Corn Gluten Meal Spray
Corn gluten meal has chemical properties that prevent crabgrass seed germination. It is a pre-emergent herbicide derived from natural sources and safe to use near children, pets and other plant life. It contains 10 percent nitrogen which benefits the surrounding turf grass. Corn gluten meal spray or granules must be applied before crabgrass germinates in early spring to be effective. It does not kill growing grass or weeds.