Crabgrass includes any of several grass species of the genera Digitaria, Eleusine and Panicum, and especially the species D. sanguinalis. Crabgrass is a warm-season, annual grass, which grows best in the heat of mid-summer. It over-winters as seed and comes up about mid-May or later. Crabgrass tends to be an open or prostrate plant that shades and smothers nearby turf plants. It is killed by fall frosts. Crabgrass is not shade tolerant, and grows best in full, hot sun. Crabgrass is likely to be more of a problem weed in warmer areas adjacent to curbs, driveways and sidewalks. Crabgrass starts germinating when soil temperatures are 50° to 55°F for 10 or more days; germination can take place over 6 weeks. Once crabgrass germinates, it rapidly dominates a turf. Crabgrass is a vigorous plant that grows faster than the most desirable turfgrasses. It grows under stress conditions such as drought, heat and low fertility where turfgrasses suffer. Crabgrass thrives under low mowing heights because of its prostrate growth habit.