Thatch is admittedly beneficial to lawns. But dethatching becomes a priority when the thatch builds up to over ½ inches.
The problem with dethatching, though, is it cancels out the benefits of thatch. The best solution remains to maintain some thatch while preventing excessive thatch buildup at the base of your turfgrass.
What is Dethatching?
Dethatching is removing excessive thatch from a lawn. Thatch is the layer of dead grass blades, stems, roots, runners, and grass clippings that pile up between the base of the grass blades that are actively growing and the soil’s surface.
Thatch forms a vegetative barrier that becomes detrimental to the health and growth of your turfgrass when left to pile up too thick (over 0.5 inches). Dethatching prevents these adverse effects from harming your lawn.
Use tools such as a hand rake, a power rake, or a vertical lawn mower (verticutter) to dethatch your turfgrass.
Pros and Cons of Dethatching Lawn
Dethatching a lawn has many benefits. It creates more air pockets in the thatch layer to enable air, water, sunlight, fertilizer, and herbicides to reach the soil easily. However, thatch also has benefits to lawn soil. Consequently, dethatching has its disadvantages.
These are the pros of dethatching.
It increases air, water, and sunlight penetration.
Dethatching allows water, air, and sunlight to penetrate the soil and reach the roots. Therefore, the roots grow deeper and stronger, improving the health of the turfgrass. Grass with an extensive root system is less susceptible to drought and heat conditions.
It reduces vulnerability to diseases.
Thick thatch creates anaerobic conditions where free oxygen is deficient. Such conditions are great for the survival of disease-causing fungal organisms such as Sclerotinia homoeocarpa, the causative agent of Dollar Spot in turfgrasses. Dethatching your turf reduces the chances of fungal diseases attacking the grass.
Some disease-causing pests/insects such as booklice and mites also thrive in the thick thatch’s moist and warm conditions. Dethatching, therefore, also helps to prevent pest infestation.
It increases fertilizer penetration.
Thatch forms a vegetative barrier. Dethatching removes the barrier and allows fertilizer to penetrate the soil more readily. Most types of turfgrass stay healthier and fill in faster when fertilizer is applied to the soil.
It increases herbicide penetration.
Systemic herbicides that enter weed plants via the roots before being transported to the rest of the plant need to reach the soil first to access the roots. These weed killers are less likely to reach the soil when a thick thatch layer forms a barrier. Dethatching allows such herbicides to penetrate the soil and reach the weed roots.
It improves overseeding success.
Thatch mixes with lawn topsoil to form a pseudosubstrate layer that new grass seed confuses for actual soil. Thatch doesn’t hold nutrients as well as soil. As a result, the grass seed that germinates in the thatch layer is barely healthy and dies easily. Dethatching enables new grass seeds to reach and grow into the soil, making overseeding more successful.
However, these are the cons of dethatching.
It makes your lawn vulnerable to weeds.
Thatch forms a barrier that prevents any weed seeds lying in the ground from receiving adequate sunlight, air, and water. As a result, it helps to suppress weed germination. When you dethatch turfgrass, the weeds seeds are exposed to optimum growth conditions.
Dethatching can dry out the soil.
Thatch limits the amount of direct sunlight and atmospheric heat that reaches the soil. Thatch slows evaporation and preserves soil moisture. Dethatching your turf exposes the soil to direct sunlight and heat retention. It leads to increased evaporation. Turfgrass might even die due to drought/lack of soil moisture.
Note: There’s a flaw in dethatching drying out the soil. Dethatching allows more water to reach the soil, as excessive thatch tends to hold rainfall/irrigation water and prevents it from reaching the soil. You can balance water penetration and dethatching if you aerate the dethatched areas.
Dethatching increases vulnerability to frost
During the colder months, thatch prevents cold air from reaching the soils and keeps lawn soil warm. As a result, a lawn with thatch is less susceptible to frost damage. The lawn becomes less cold tolerant and is more likely to suffer from frost damage in the winter after dethatching.
Dethatching exposes your lawn to turf injury.
Incorrectly dethatching a lawn using aggressive tools like a power rake or a vertical lawn mower can cause excessive turf injury, especially in turfgrass types that spread via stolons but lack stolons.
Incorrect use of dethatching tools includes setting the blade height to close. The blades of the dethatching tool cut through the above-ground runners, making it difficult for the turf to recover.
Can you dethatch wet grass?
Technically, you CAN dethatch your lawn when it’s dripping wet. But you shouldn’t. You expose the lawn to physical damage when you use dethatching tools. Additionally, wet thatch tends to clog the tines of power dethatching tools, making them less effective and the job more strenuous. Therefore, it’s best if you avoid it.
However, dethatching is best done when the lawn is only slightly moist. To ensure your turfgrass isn’t excessively wet but is moist by the time you detach, lightly irrigate the lawn two days before dethatching.
Tips to prevent thatch buildup?
The most effective ways to prevent excessive thatch buildup include watering accordingly, aerating the lawn soil, adjusting soil pH, and applying a liquid dethatcher.
Some turfgrasses, such as centipede grass, require minimal water to thrive. They are also more likely to develop thatch if overwatered. However, this doesn’t mean that you should leave the lawn to dry out completely. The soil needs some moisture so that thatch can decompose.
Note: Water the lawn deeply. We recommend one inch of water every week. You keep the soil moist and avoid waterlogging.
Aerate the lawn
Thatch is simply an organic matter that hasn’t yet decomposed. As such, core aeration of lawn soil prevents thatch buildup by relieving soil compaction and boosting microbial activity in the soil.
With more decomposing bacteria in the soil, thatch is broken down faster and is less likely to build up to detrimental levels.
Monitor and adjust Soil pH
Changes in soil pH sometimes lead to reduced microbial activity, resulting in thatch buildup. Regularly monitor your soil pH and adjust it accordingly to prevent excessive thatch. If the soil is too acidic, add lime to raise the pH.
Note: The ideal soil pH for soil bacteria involved in thatch decomposition is 6.5. A pH below 6 is too acidic and reduces microbial activity.
Apply a Liquid Dethatcher
While dethatching tools like rakes and vertical mowers are usually used when the thatch buildup is already excessive, you can use a liquid dethatcher while the thatch layer is still light to prevent it from piling up. Liquid dethatchers or biological dethatchers contain bacteria and enzymes that speed up the rate of thatch decomposition, thereby preventing the thatch layer from becoming too thick.