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Thatch is the woody parts of the grass plant - stems, roots and stolons (above-ground roots) - that accumulate above the soil. Thatch is not grass clippings, which break down and return to the soil quickly. In plug or core samples, thatch is the brown, fibrous layer on top of the soil. A moderate thatch layer, about 1/2 inch, protects the soil from erosion, binds plants together to resist wear, and cushions falls from people playing on a turf area. But much more than 1/2 inch can be a problem, reducing aeration and water infiltration. Extreme thatch buildup (several inches) causes the active roots of the grass plant to grow in the thatch layer rather than the soil, making the lawn nutrient-starved and prone to drought stress. Excess thatch accumulation is associated with over-fertilization (chemical based fertilizers) and heavy broadcast use of pesticides. Over-watering, or frequent shallow watering, may also promote thatch accumulation by promoting surface rooting. Bentgrass lawns are prone to thatch accumulation, and must be mowed at the proper height (about 1 inch), fertilized with organic fertilizer and be treated with Liquid Organics to avoid thatch buildup. In natural grass ecosystems, earthworms constantly deposit nutrient- and microbe-rich castings in the thatch layer, which accelerate the fungal and bacterial breakdown of thatch and its recycling into nutrients available to the grass plant. On lawns with excess thatch accumulation (over 1/2 inch), this natural breakdown process can be enhanced by aeration, mulch-mowing, topdressing with thin layers of mature compost in the spring and fall, and more moderate (less total nitrogen) fertilization with organic fertilizers and Liquid Organics. Organic fertilizers and Liquid Organics are known to help decrease thatch thickness and increase earthworm and microbial populations. Historically, in extreme cases, (when thatch thickness is more than 1 inch) power de-thatching was used on a one-time basis, in the spring or fall when the lawn was actively growing. Prior to de-thatching, the lawn was "scalped" by mowing as short as possible. The process involved two or three passes at 90 degree and then at diagonal angles, the thatch was raked out and removed for disposal. This 'old way' of dethatching required a lot of work, did considerable damage to the lawn's root system, as well as it's appearance and generated significant landfill material.
The current, and preferred method of dethatching a lawn consists of: aeration, organic fertilizing, Liquid Organics applications, or topdressing with compost. Not only is this method more cost effective, it builds a healthy soil that retains nutrients and improves the natural defenses to diseases and pests. It is preferable to break down the excess thatch with Liquid Organics or compost topdressing, changing to organic fertilization, and eliminating the use of pesticides. The Lawn Jockey 360.876.3734Balancing the Ecosystem
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while building sustainability.