A Lawn Covered in Weeds

Thatch

• A thick thatch layer over 1/2 an inch is a common culprit behind a high population of weeds. Thatch is the organic dead and living material that builds up between the soil and the grass blades. When lawns have a thick thatch layer, grass is unable to develop strong root systems for spreading. Weeds take advantage of grass' inability to spread and pop up in bare areas. To check your thatch layer, cut out a 2-inch wedge-shaped piece of turf and measure your thatch. Push a power dethatcher over your yard to remove the thick layer of thatch.

Lawn Compaction

• Compacted soil prevents adequate soil drainage and air flow. When grass grows on compacted soil, turf is unable to spread and is at a greater risk of fungal disease. Fungal disease kills off areas of the grass, and weed seeds germinate in bare or thinning parts of the lawn. Gardeners use core aerators to rip up plugs of soil to allow better drainage. Push the core aerator over your lawn to increase its draining abilities.

Soil Preparation

• All weeds must be removed before you can sow grass seeds. To remove weeds from the lawn, spray them with an herbicide that contains glyphosate. Glyphosate kills off weeds without leaving behind soil residue that harms grass seeds. If you are renovating the entire yard, spray your existing turf grass with the herbicide. Gardeners who overseed thin, weedy lawns should mow their lawns down to 2 inches in height to prevent grass from competing with grass seedlings.

Sowing

• Sow your grass seeds at their specific recommended distribution rate. For example, Kentucky bluegrass must be sown at a rate of 2 to 3 lbs. per 1,000 square feet, according to the University of Minnesota. Cover your grass seed with 1/8 of an inch of compost. If you sow on a bare lawn, push a lawn roller over the grass seed to achieve good soil-to-grass-seed contact. Water the soil area to promote grass-seed germination.