Once determined that a lawn is in need of dethatching, here are a few tips to give an idea of what is involved. Care must be taken not to try and remove all thatch from a lawn at one time. This will cause more harm than good and can actually kill the grass. Unless, the lawn has extremely heavy thatch buildup, regular aeration treatments would be better.
When to use dethatching – Dethatching is the process or removing Thatch from the lawn. As a general rule of thumb, up to 1/2 inch of thatch is normal. Remember, thatch can be good for lawns, especially during times of drought, water restrictions, and high heat, when it can act like insulation for the soil by providing a screen from sun light and help to hold in moisture. When thatch has accumulated in excess of 1/2 inch will be terrible disadvantage to a lawn. The reason is it creates too much buffer between the soil and the grass, thereby preventing sufficient amounts of water, air, and nutrients (fertilizer) to reach the soil. Excess thatch can also encourage the proliferation of pests such as Chinch bugs, insects, and various lawn diseases and fungi.
To help determine how much thatch buildup exists in a lawn, simply take a narrow wire or screwdriver and place it in the thatch until it reaches the soil. Mark how high the thatch reaches up on the wire/screwdriver and hold it next to a tape measure or ruler to determine the depth. If there is an excess of thatch in more than one place in a lawn (usually more the 1/2 inches), then it might be time to dethatch. If an excess of 1 inch of thatch in a lawn, then seriously consider dethatching soon. Much like aerating, dethatching should be done when your lawn can best recover, usually not during times of drought, water restrictions, and heat waves. For most lawns this is either in the late spring or early fall.
Step by step process
Don’t fertilize the lawn for at least 45 days prior to dethatching.
Plan to apply preemergence herbicides, do so after dethatching (Otherwise, the herbicides may bind with the thatch and decrease their effectiveness).
For best results, it is better to dethatch after a light rain or water the lawn. Avoid dethatching when the soil is saturated after heavy rainfall. The reason for this is that the dethatching equipment will pull the soil and tear at the roots instead of slicing and lifting the thatch.
Mow the lawn to the lowest recommended height for that particular lawn grass. Bag the clippings.
Avoid machines with flexible rake-type tines and dethatchers that attach to a rotary mower blade. These cause more damage than benefits.
When using a power dethatcher, locate all buried cables (i.e. landscape lighting, cable tv, phone, electric, etc.) and underground sprinkler lines and sprinkler heads.
For small areas, use a cavex rake. The tines are actually sharp blades and more effective than using a regular garden rake. Pull the rake across the lawn, bringing the thatch up to the soil surface. DO NOT OVER-DO THE MANUAL RAKING PROCESS.
When using a mechanical dethatcher, it is better to set it too high than it is to set it too low. It is better to go back over spots several times so the blades don’t tear up the lawn.
Power rakes and vertical mowers available through rental shops are generally lightweight and low-powered. This will require several passes to bring up the thatch. Make the 2nd pass at right angles to the first pass.
A lot of debris will be generated. Remove this debris.
Fertilize the lawn with a regular fertilize (non-weed & feed).
Water the lawn. This helps prevent excessive drying and helps the grass recover faster.