Thatch is a layer of undigested roots, leaves, and organic plant material that settles between the turfgrass and the soil surface. It is a tightly intermingled layer of stems, leaves, and grass roots that accumulates between the vegetation and the soil. Thatch build-up begins when turf produces organic debris faster than it can be broken down. The layer of thatch not only looks spongy, but it functions as a sponge as well. Most of the water from rain or irrigation is trapped in this layer of organic matter, which means the grass roots don’t have an incentive to grow deeply in search of water because the water remains at the top of the soil.
A thin layer of thatch in lawns (½ inch or less) provides insulation against temperature extremes and fluctuations in soil moisture. Some thatch on sports turf (about ½ inch) provides much-needed resiliency, softens players impact on the surface, and improves footing. However, if your lawn has more than an inch of thatch, turf problems will likely result. A thick layer of thatch, more than one-half inch, can be a detriment to your lawn.
Pros and cons of thatch include:
Pros:
- Provides insulation against temperature extremes and fluctuations in soil moisture
- Provides resiliency, softens players impact on the surface, and improves footing on sports turf
Cons:
- Easier for mowers to scalp the lawn (because the wheels sink into the soil and the crowns are higher than normal)
- Shallow root system (roots don’t dig deeply into the soil to look for water)
- In hot weather, roots may dry out; in wet weather, roots are too wet and deprived of oxygen
- Fungus and pest problems
- Prevents air, water, fertilizers, and lawn treatments from reaching the soil level
If your lawn has more than an inch of thatch, preventative practices wont provide adequate control, and thatch must be physically removed. Use vertical mowers with blades that are perpendicular to the turf surface. As the unit moves over the turf, the rotating blades slice into the thatch, bringing it up.
