WHAT THATCH ACCUMULATION IN A LAWN?
What Causes Thatch to Buildup in a Lawn?
Short Answer: A Lack of Beneficial Microbial Activity
Thatch accumulates in a lawn when the production of dead organic material exceeds the ability of microorganisms in the soil to break it down. This occurs when more organic matter is being created daily than is being decomposed.
The most significant thatch buildup typically happens in lawns with “dead soils,” and thatch is a symptom of a larger issue: the lack of beneficial microbial activity. Thatch accumulation can occur due to poor soil aeration and drainage. Additionally, improper lawn watering practices—such as excessive or overly frequent watering—cold soil temperatures, the use of chemical pesticides, and reliance on synthetic fertilizers all contribute to a poor environment for microbes and the increase of thatch in lawns.
When the thatch layer in a lawn exceeds 3/4 of an inch in thickness, it may be necessary to mechanically remove it through methods such as power raking or vertical cutting.
Improper Lawn Care Practices That Kill Microbes and Cause Thatch Buildup in Lawns
- Shallow or frequent lawn watering practices.
- Severe overwatering of the lawn.
- Fertilizing the lawn with fast-release nitrogen. Salt-based nitrogen like those found in synthetic fertilizer sources will kill microbes in the soil.
- Mowing the lawn infrequently where more than 1/3 of the blade of grass is removed.
- The use of lawn herbicides and lawn fungicides. Both of these have been proven to kill microbial activity in soils.
- Compacted soils that have not been aerated annually.
Thatch that is 1/2 inch or less is considered normal. More than 3/4 inch of thatch can be a major problem for the lawn.
What is Lawn Thatch?
Lawn thatch is a dense layer made up of intermingled stems, leaves, and grass roots that accumulates between the grass and the soil. Some thatch is beneficial, but excess thatch can increase the turf’s vulnerability to lawn diseases and reduce its ability to withstand drought, cold, and heat stress. It also obstructs the flow of air, water, fertilizers, and nutrients into the soil. In severe cases, grass roots may only develop within the thatch layer instead of extending into the soil, making the turf even more susceptible to drought and heat stress.
Why is Yearly Dethatching is Unnecessary?
If a lawn is accumulating thatch faster than beneficial microbes can break it down, it indicates a deficiency of these microbes in the soil. The solution to a thatch problem is not to physically remove the thatch, but to manage it by addressing the improper cultural practices that harm soil microbes. To prevent and resolve a thatch issue, it is essential to stimulate beneficial microbial activity in the soil rather than mechanically removing the dead grass.
In fact, over 99.99% of lawns do not require thatch removal through power raking or vertical cutting. Before scheduling or performing a power raking service, please consult with your local lawn care expert.
Lawn aeration is an excellent way to stimulate beneficial microbial activity in soils. Air is vital to soil health and aeration should be perfromed at lease once per season.
Steps to Stimulate Microbes and Repair a Thatch Problem in a Lawn
How To Manage Thatch Buildup in a Lawn
- Start by stimulating beneficial microbial activity by implementing proper lawn watering practices, lawn mowing practices, core aeration, and organic lawn fertilization.
- Power raking is a tool that can be used as a last resort to manage a major thatch problem, but power raking is not the cure for the thatch problem. Power raking or vertical cutting is only recommended in the most severe cases of thatch and only when performed before the lawn comes out of dormancy.
- Power Rake, but only if it is before the lawn has greened up in the spring. This lawn care service is rarely necessary
- Double Aeration to bring air into the soil.
- Sprinkler Audit to fix any improper lawn watering practices. Make sure to follow the principles of the 1-2-3-2-1 lawn watering technique.
- Stop all fast-release nitrogen, synthetic fertilizer, herbicide, or fungicide applications.
- Apply Synergy with Corn Gluten Meal and Humate Soil Conditioner to stimulate beneficial microbial activity.
- Compost top dressing applications are the fastest way to introduce millions if not billions of microbes into the lawn.
Following the 1-2-3-2-1 lawn watering technique is the best way to reduce thatch buildup.
An Idiots Guide to Thatch in a Lawn
Thatch is a layer of organic material, consisting of dead and living plant stems, roots, and shoots, that accumulates between the soil surface and the green grass blades in a lawn. While a thin layer of thatch (less than 0.5 inches) is beneficial, as it provides insulation and helps retain moisture, an excessive layer can harm the lawn by restricting air, water, and nutrient penetration.
Causes of Thatch Buildup
- Overwatering: Promotes shallow root growth and increases organic debris that doesn’t decompose efficiently.
- Overfertilizing: Especially with synthetic nitrogen-heavy fertilizers, which can encourage rapid grass growth but slow down microbial decomposition.
- Grass Type: Some grass species, like Kentucky bluegrass, naturally produce more thatch.
- Poor Soil Aeration: Compacted or heavy clay soils hinder microbial activity, slowing the breakdown of organic material.
- Low Microbial Activity: A lack of microorganisms in the soil reduces decomposition of organic matter.
Signs of Excess Thatch
- The lawn feels spongy when walked on.
- Grass struggles to grow evenly or appears stressed despite adequate watering and fertilization.
- Water gets stuck in the thatch instead of soaking into the soil.
- Brown patches or thinning grass, especially during heat stress.
Managing and Preventing Thatch
Preventative Measures
- Proper Mowing:
- Cut grass tall to promote deeper digging grass roots.
- Avoid cutting more than one-third of the grass blade at a time.
- Water Correctly:
- Water deeply and infrequently to encourage deep root growth.
- Avoid daily watering.
- The lawn might look worse before it looks better after adjusting the lawn watering.
- Balanced Fertilization:
- Use organic fertilizers and avoid overuse of nitrogen.
- Aerate the Lawn:
- Aeration improves soil drainage and promotes microbial activity to decompose organic matter.
- Encourage Microbial Activity:
- Add compost or organic matter to boost soil health and microbial life.
Treatment for Lawns with Excessive or Severe Thatch
- Dethatching Tools:
- Use a dethatching rake for small areas with moderate thatch.
- Power raking may be necessary for larger lawns with thick excessive layers.
- Core Aeration:
- Use a core aerator to remove soil plugs and introduce oxygen into the soil. Double aeration may be necessary for lawns with a severe thatch problem.
- Topdressing:
- Apply compost or sand after dethatching to promote decomposition and improve soil structure.
Thatch buildup should not occur if the soil is teaming with microbes. You can prevent thatch buildup and keep your lawn thriving with proper mowing, watering, and organic fertilization.
This core sample shows a thatch layer of 1 inch. This lawn is suffering from a severe thatch problem that was caused by improper watering and fertilization practices.
For a comprehensive plan to manage your lawn's thatch issue call our office at (303) 499-2000 Boulder or (970) 225-9425 Fort Collins.
FAQ – Symptoms of Under Watering a Lawn
How to water a lawn with clay soil?
Proper lawn watering using the 1-2-3-2-1 lawn watering technique is the best way to water a lawn with clay soils because it will help prevent soil compaction. The best way to improve a clay soil is to create an environment that is teaming with microbes, a.k.a. a living soil.
A wonderful organic lawn care product that is designed to bust up clay soils is Humate soil conditioner. Humate is scientifically proven to stimulate microbial activity in the soil. Lawn aeration is also an important lawn care service that will help alleviate soil compaction and break up the heavy clay content of soils.
How much water does a lawn need to stay green?
Grass requires different amounts of water depending on how much sun the lawn receives. For instance, a south-facing lawn in full sun will require .6”-.7” of water, a normal-facing aspect with partial sun will require .5”-.6” of water, and a north-facing aspect or lawns in full shade will require .4”-.5” of water per watering.
Every sprinkler system is different and the output of each sprinkler zone on an irrigation system is different too. The best way to determine how long to water a lawn is to get an accurate measurement of each zone in a sprinkler system. Using a rain gauge or a flat-bottomed flat-sided container is the best way to get an accurate measurement.