The hotter than normal conditions this season is resulting in the appearance of crabgrass earlier than usual in those lawns that are not growing under the most ideal of conditions.
Crabgrass is an annual weed. It grows well in conditions that desirable grasses do not do well in, including: soils that are low in calcium, compacted and acidic. Since crabgrass needs warmer soil conditions; you will not find it in shady areas of your lawn. You will find it in sunny areas of the lawns; especially along walks and driveways where the radiant heat from the asphalt or brick helps warm the soil. These areas also tend to have poor soil conditions because of the stone pack found along the edges. Another favorite area for crabgrass is on top of the leach field for septic systems.
What to do about it now? The best thing is get ready to improve the soil conditions come fall (only a couple of weeks away). Top-dress and heavily over-seed these areas come early September. If your soil test results warrant it make certain that you lime. Also fall is the best time to aerate your lawn. All these activities will encourage a healthier stand of turf for next season. Remember to mow high throughout the season!
Many folks attempt to control a crabgrass outbreak by lowering their mowing height. This is perhaps the worst thing they could do. Crabgrass plants are very adaptive to mowing height. Plants can produce seeds at mowing heights as low as 1/2-inch. Crabgrass reproduces by seeds. It has a prolific tillering or branching habit. A single plant is capable of producing 150 to 700 tillers and 150,000 seeds.
Establishing a dense and healthy stand of turfgrass is the best way to control crabgrass and other annual weeds, including grasses and broad-leaf weeds. The proper mowing height and frequency, fertilization and irrigation are part of the weed control program and should be practiced throughout the growing season.