Lawn Thatching

Why is Too Much Thatch Bad?

• Prevents water and nutrients from reaching the plant roots.
• Absorbs pesticide/fungicide, preventing them from doing their job.
• Reduces space available for new grass. When crowded by thatch, new grass tends to grow rapidly as they seek light and space, thus producing long, thin leaves with shallow roots.
• Grass root systems can grow into the thatch rather than into the soil.
• Harbors diseases such as bipolaris leaf spot, summer patch, and dollar spot.
• Aggravates insect problems. Thatch favors insects by hiding them from their predators.

What is thatch and how to prevent it in your lawn?

Grass thatch is a tightly intermingled organic layer of dead and living shoots, stems, and roots that accumulate just above the soil surface of your yard.

It's not necessarily grass clippings even though they may contribute to the problem. Thatch accumulation is due to either over-fertilization, over-watering, and/or soil compaction of the lawn.

While a small amount of it is helpful as it helps regulate soil temperature and moisture of the lawn, too much of it interferes with air and water intake and makes proper lawn care difficult.

Too much of it can also reduce how effective fertilizers and pesticides are and increase disease and insect activity. Eventually, roots may start growing in the thatch, and since it does not hold much water, the lawn can become victim of drought.

Many people interested in lawn care aren't familiar with thatching; or know why they might need to be concerned. Thatch is a layer of living and dead organic matter that accumulates on top of the soil, just beneath the grass.

Thatch is mostly made up of living turfgrass stems and roots, and decaying or dead grass and debris in the process of breaking down and becoming part of the soil. Grass continually renews itself and thatch is a normal part of that renewal process. It's not unusual for a yard to have thatch. The older and more established a lawn is, the more likely it has thatch to some degree. Some thatching can be beneficial as it insulates lawn roots from extreme cold in winter and excessive moisture loss in summer. But sometimes, due to environmental factors or improper lawn care practices, thatch accumulates faster than the dead matter can breakdown and become soil. Excessive thatch (more than 1/2 inch thick) encourages pests and disease, discourages healthy grass rooting, and can interfere with some lawn care practices.

Lawn care can have a major impact on thatching. For example, excessive nitrogen fertilizer applications or frequent overwatering can contribute to thatch, because they cause the lawn to grow too fast. Some people mistakenly blame grass clippings dropped on the lawn after mowing as a cause of thatch buildup. Clippings are very high in water content and breakdown rapidly when returned to lawns after mowing, actually helping reduce thatch. This assumes lawns are properly mowed on a regular basis (not removing more than one-third of the leaf blade at a time) at the correct height.

Environmental factors that contribute to thatching include heavy, wet soils; alkaline, or high pH soils; and soil compaction. Kentucky bluegrass, hybrid Bermuda and Zoysia are notably prone to thatching.

Lawn Care Aeration and Thatching

If thatch levels accumulate to more than 1/2″ lawn problems may occur and the thatch will have to be controlled. You could use a garden rake - those with metal or steel tines - or a special dethatching rake to scrape out the thatch, but you risk tearing out live grass roots with it. Core aerating helps degrade thatch and also helps solve some of the causes of thatch. Core aeration followed by topdressing with compost will generally correct the reasons thatch is accumulating. Lawn care aeration slows thatching by pulling soil cores to the surface that, when left on the ground, act like topdressing. The holes created alleviate problems such as compaction or poor drainage. Topdressing is simply adding a thin layer (1/8″ to 1/4″) of good rich soil, such as mature compost, over the lawn and gently raking it down into the thatch. This adds beneficial microorganisms to speed thatch breakdown.

With proper lawn care, thatching is nothing to be overly concerned about...when you know exactly what to do.