What is Thatch?
Thatch refers to the accumulation of dead grass, decomposed grass roots, leaves, and, in some cases, living grass roots that naturally form in a lawn. While a small amount of thatch in a lawn is normal and can be beneficial, it becomes problematic when it grows too thick and decays. Excessive thatch can block air, water, and nutrients from reaching the grass roots, leading to weak and unhealthy grass growth. Additionally, thatch is a primary cause of moss growth on lawns.
There are two types of thatch in a lawn: surface thatch and sub-surface thatch.
Surface Thatch
As grass grows, is mowed, and undergoes seasonal changes, a layer of thatch quickly develops above the soil line. This layer can hold moisture, protect the grass from drying out, and keep the soil cool, which is beneficial in moderation. However, when surface thatch becomes too thick, it prevents grass roots from penetrating the soil and creates ideal conditions for moss growth. This results in a spongy, mossy lawn.
How Do You Keep on Top of Surface Thatch in a Lawn?
Regular maintenance, such as annual scarification or lawn thatch removal, is key to keeping surface thatch under control. Scarification involves removing excess thatch and debris from the lawn, improving air circulation, water retention, and nutrient absorption. This process helps your grass thrive by reducing thatch buildup and preventing moss from taking over. For more information about Scarification, click here.
Sub-Surface Thatch
Sub-surface thatch is a layer of dead organic matter which forms a mat between where the soil line should be and the soil. Often the soil line becomes the top of the sub-surface thatch layer. This barrier makes for a very weak, prone to moss and disease lawn.
Lawns often have surface and sub-surface thatch at the same time. If a lawn has sub-surface thatch it will usually have surface thatch too.
You cannot just slice the thatch layer off the lawn, it has to be thinned out by removing vertical cores.
How do you thin out Sub-Surface Thatch?
Hollow-Tine Aeration, which removes thousands of plugs or cores from the lawn, is the most effective form of thinning out sub-surface thatch. For more information about Aeration, click here.
The image below shows the effect on a lawn before and after Aeration.
