A common myth of lawn care is that leaving grass clippings on your lawn will contribute to the problem of thatch--the unsightly web of brown stems and apparently dead grass that weaves close to the soil. Thatch is actually a normal part of grass growth for two reasons. Firstly, the grass reproduces through sending out rhizomes and stems. Secondly, thatch consists of visible roots. Many homeowners choose to rid the lawn of thatch by removing it with special machines.
Reasons to Dethatch
Too much thatch--more than 1 inch--keeps water and nutrients from getting to the soil. The thatch stays moist which makes it an ideal breeding ground for fungus that can ruin a lawn. Once it is removed it works well as composting material or a temporary mulch as long as it has not be treated with herbicide.
Dethatching is best done in the spring when the lawn is dry, and on a regular basis every two years or so. If it is left too long it may build up and create a larger job removing it. Many home and hardware stores rent dethatching machines that are simple to use. Guided over the lawn much like a lawnmower, they use metal fingers to reach down into the grass and pull the thatch up to deposit into a bag.
Manual dethaching is possible with a special rake but the work is hard unless it is a small lawn. The thatch can be difficult to pull up. Special dethatching attachments are sold for converting lawnmowers to a dethatcher but Tom Cook, turf grass specialist with the Oregon State University Extension Service, does not recommend them as they are rough on a lawnmower.
Some homeowners do not like to dethatch their lawn because it makes the lawn look ragged and beat up for several weeks. However, with the thatch gone it is an ideal time to put fertilizer and new grass seed down. There will be much better soil contact and any holes left behind by the dethatcher will quickly fill in. The existing grass will also have an opportunity to grow more efficiently.