Dead grass and other debris cause thatch in lawns. The thatch in lawns can cause brown spots in the grass. Once the thatch is removed, more oxygen can reach down to the grass roots. Various types of thatching blades are available for many types of lawn mowers. Individual thatching blades will come with specific instructions for installation. Once the lawn is thatched, new grass seed can be sown into the grass to fill in any patchy or brown areas.
Install the thatching blade onto the lawn mower. Follow the thatching blade manufacturer's instructions for specific details.
Run the lawn mower, with the thatching blade attached, in one direction over the lawn; for instance, in an east and west direction only.
Remove the pulled up thatch material with the leaf rake. Collect the material into small piles. Move the small piles into a newly formed compost pile for breaking down the material into rich humus. Some city agencies may have compost services available. Contact your local recycling agency for such programs.
Pull more thatch from the grass by running the lawn mower across the first path in the opposite--north and south--direction. Thatching the lawn at a 90-degree angle to the first thatching path will remove even more material and aid in slightly aerating the soil.
Rake the material from the lawn. Collect into the compost piles.
Plant new grass seed of the same species over the newly thatched area. Consult the seed labels for amounts to be planted and any watering requirements. The new seed will quickly germinate due to the bare soil under the lawn's surface of grass blades.