Thatch in St Augustine Lawns


By Rick Orr
Soil Profile below a St Augustine Grass Lawn with a ruler showing depth
Below the canopy of a St Augustine lawn, the conditions are moist, cool, dark and windless. This is perfect for the composting of organic matter that can form a thatch layer

What is Thatch

Thatch is a layer of organic matter on the soil surface that forms when conditions prevent the enzymatic digestion (composting) of organic matter. Thatch forms a barrier to oxygen, water, and nutrients. It is a dead zone above the soil that chokes the life out of anything below the thatch.

The solution for thatch is to provide the conditions needed to compost organic matter - moist, cool, dark and windless conditions just above the soil surface where organic matter collects.

An Augustine Lawn is Thatch Free

A St Augustine lawn kept tall and wet always has moist, cool, dark and windless conditions at the soil surface. The tall canopy shades and cools the soil and blocks the wind. An irrigation system or rain keeps the organic matter wet and the tall canopy stops evaporation of the moisture. Any organic matter that collects on the soil surface in a St Augustine lawn is composted into plant nutrients.

Composting is the enzymatic digestion of organic matter (OM) by bugs, worms, microbes, fungi, and algae that thrive in the moist, cool, dark, and windless conditions below the canopy. Bugs and worms chew, grind and digest the OM. Microbes, fungi, and algae further process the OM that is eventually used by the St Augustine plant as food. It is a sustainable food system for the lawn.

St Augustine Lawn Lives Above Ground

St Augustine lawn is made of thick above-ground stems with large open space between stems and a tall stiff canopy above the stems. It is this mat of stems and stiff canopy that is often – and wrongly – called thatch. This mat of stems and tall canopy is what provides the moist, cool, dark and windless conditions to prevent thatch.

Fat Grass

During peak growing conditions – hot, rainy and open sun – the growth rate can be excessive in areas of the lawn. The stem mat becomes excessive and mowing is difficult due to the spongy character of the lawn. This is not thatch – it is fat grass, where too much grass is growing in too little space. This is self-correcting. As peak conditions wan, the growth will slow, and the fat grass will become slim again.

Mowing Height is Critical for Composting

Mowing height is critical for composting and protection of stems and roots from the hot Florida sun. Mowing heights of 4” or higher will provide a thick tall canopy providing optimum light reception, insulating of the stems from the harsh sun and perfect conditions for composting. That is a win/win/win – high photosynthesis, max protection for the stems and composting.

Good Action Plan for Thatch in St Augustine Lawns

The spongy cushiony feel of a St Augustine lawn is natural and necessary for the survival and health of a St Augustine lawn and composting of organic matter. For best results keep the lawn tall and wet - mow your lawn at 4” or higher and spend your time and money improving your irrigation system and don’t worry about thatch.

Rick Orr Owner-Staff Agronomist Barefoot Grassl/Creator of ILOVETURF.COM
Staff Agronomist at Barefoot Grass

Since 1995, Rick Orr has worked in Pinellas County providing turf management and pest control. Rick Orr is a graduate of VA Tech in Agronomy (Turf Ecology) and the creator of 

Since graduating from VA Tech in 1979, Rick worked in the green industry, mostly with golf courses, resorts, and large communities. Rick has obtained certifications in arboriculture, landscape, irrigation, and taught Environmental Horticulture at St Petersburg College. 

Currently, Rick is the Staff Agronomist at Barefoot Grass in Largo, FL. To learn more about Barefoot Grass Free Price Quote from Barefoot Grass for Home Pest Control and/or Lawn Care 

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