Digitaria
Digitaria is a genus of plants in the grass family native to tropical and warm temperate regions but can occur in tropical, subtropical, and cooler temperate regions as well. Common names include crabgrass, finger-grass, and fonio. They are slender monocotyledonous annual and perennial lawn, pasture, and forage plants; some are often considered lawn pests. "Digitus" is the Latin word for "finger", and they are distinguished by the long, finger-like inflorescences they produce. Uses. The seeds are edible, most notably those of fonio ("Digitaria exilis" and "Digitaria iburua"), "Digitaria sanguinalis", as well as "Digitaria compacta". They can be  toasted, ground into a flour, made into porridge or fermented to make beer. Fonio has been widely used as a staple crop in parts of Africa. It also has decent nutrient qualities as a forage for cattle. Lawns. The prevalent species of "Digitaria" in North America are large crabgrass ("D. sanguinalis"), sometimes known as hairy crabgrass; and smooth crabgrass ("D. ischaemum"). These species often become problem weeds in lawns and gardens, growing especially well in thin lawns that are watered lightly, under-fertilized, and poorly drained. They are annual plants, and one plant is capable of producing 150,000 seeds per  season. The seeds germinate in the late spring and early summer and outcompete the domesticated lawn grasses, expanding outward in a circle up to in diameter. In the autumn when the plants die, they leave large voids in the lawn. The voids then become prime areas for the crabgrass seeds to germinate the following season. Biological control is preferable over herbicide use on lawns, as crabgrass emergence is not the cause of poor lawn health but a symptom, and it will return annually if the lawn is not restored with fertilization and proper watering. Crabgrass is quickly outcompeted by healthy  lawn grass because, as an annual plant, crabgrass dies off in autumn and needs open conditions for its germination the following spring.