How to Remove Excess Thatch from Your Lawn

Once used for roofing for its ability to repel water, thatch is the build-up of grass clippings, grass roots, pine needles, tree leaves, small twigs and moss. This organic material creates a tangled bed that can prevent water and fertilizer from reaching grass roots. A thin layer of thatch, less than half an inch, is expected and necessary for your lawn's health. This thin layer decomposes, and the decomposed material feeds your lawn. But when it builds up, the material does not decompose quickly enough and blocks water from reaching the roots. The two common causes of thatch build up are over-watering and over-fertilizing. The best times to de-thatch your lawn are in early spring or at the onset of cooler weather. How you de-thatch depends on the depth of the thatch and the size of your lawn.

1. Determine the depth of your thatch. Using a small shovel dig out a square of lawn approximately 4 square inches in area and 2 to 4 inches in depth. You need to see the soil, the layer of thatch and the full length of your grass.

2. Measure the depth of your thatch with a ruler. The thatch ranges from wheat colored to darker brown and looks like a tangle of thick threads. If the depth is less than 1/2 inch you can allow the thatch to stand. You should, however, aerate your lawn to keep the thatch loose. This will aid in decomposition.

3. Use a metal rake if the thatch is more than 1/2 inch thick but less than 1 1/2 inches thick, and your lawn is relatively small, less than 1000 square feet. Use short deep strokes to cut into the thatch and then pull the rake back toward you. This will pull up manageable sections of thatch.

4. Bag or otherwise contain the thatch. Thatch can be added to your compost heap. It will decompose once it's exposed and separated from the soil.

After pulling the thatch from your lawn, you may notice it looks patchy and unkempt. Give your lawn a deep watering every three to five days, for two to three weeks. After that, water deeply once a week or less, if you live in a wet climate. Do not fertilize until early fall if de-thatching in spring or the following spring if de-thatching in the fall.

If your thatch is thicker than 1 1/2 inches, you may need to use a mechanical de-thatcher, otherwise known as a power rake.

You can rent a de-thatcher at your local home improvement store. Set the blades to cut into the soil surface from 1/8 to 1/4 inch. Set the distance between blades from 1 to 2 inches apart. You will need to test a small area to find the right settings. The blades should scar the soil and pull up thatch without tearing out grass. The scarring is actually aeration of the lawn; this will loosen the soil and allow air to reach the roots.

Again, your lawn may look patchy and appear damaged after using a de-thatcher. Water deeply and don't fertilize until the end of the season or until the beginning of spring.

A Word About Fertilizer

Fertilizers are important to your lawn, but should be used sparingly. Grass is sensitive to the chemical make-up of fertilizers and if applied in too great a quantity or even at the wrong time of day, the fertilizer will "burn" your lawn. The type of fertilizer you need depends on the type of grass you have, the local climate and the overall health of your lawn. Check with your local garden center for information regarding your lawn's particular fertilizing needs.