Thinning grass, bare patches and an increase in weeds can all indicate thatch build-up in your lawn. Excessive lawn thatch is a common problem that is best treated in the spring when turf grass is in a vigorous stage of growth. Correcting the problem is straightforward, although it can be very hard work if done by hand.
Thatch occurs naturally in every lawn. It consists of decomposing roots, grass clippings and other organic material that forms between the grass and soil. A thin layer of thatch is beneficial to your lawn as it provides essential nutrients to the soil. However, if this layer becomes too thick, it can become a barrier that prevents air and water from penetrating the soil. Under these conditions the soil starts to compact and grass roots are deprived of both food and water. A healthy layer of thatch should be no more than a 1/2-inch deep.
Determining the amount of thatch in your lawn is easily done. Cut out a small section of turf about 6 inches deep using a garden spade. Between the grass and the soil will be a light brown layer of decomposing material which is the thatch. If this later is more than 1/2-inch thick, you will need to dethatch the area. Examining turf sections from different locations will tell you if the entire lawn should be treated or if the problem is confined to certain spots.
Dethatching By Hand
Small patches of grass can dethatched by hand using a thatching rake. These rakes are specially designed with v-shaped tines that cut through the thatch layer. A hard-tined scarifying rake may also be used but it will not remove as much material. Cut the grass as short as possible and remove the clippings before you begin. The trick to effective dethatching is to push the tines deep enough to cut the thatch without also cutting the grass roots. Constant pressure must be maintained on the rake while pulling to keep it at the right depth.
If the whole lawn needs treatment, it's best to rent a dethatching machine. Many tool rental shops have power rakes and vertical cutters. These machines are quite powerful and can easily damage a lawn if not used properly. Practice on a small section of lawn that is hidden from view until you are comfortable with the operation of the equipment. Many people hire contractors to do the dethatching for them. Landscape maintenance professionals can also aerate your lawn which is essential to relieve soil compaction.
Committing to an annual lawn maintenance routine is the most effective way to prevent a thatch problem. Aerating the lawn each spring will go a long way to reducing the thatch build-up. An aerator removes small cores of turf in a regular pattern which increase the flow of air and water to the soil. Thatch will decompose faster after aeration as deeper microorganisms rise to the surface. Follow up with a top dressing of sand and grass seed in the fall to strengthen the turf and soil.