by Lisa Courtney, Customer Support, Red Hen Turf Farm
At certain points throughout the year, we start getting calls asking, “Do I need to be thatching my yard? It looks like I’ve got a LOT of thatch.”
So, what is thatch?
First of all, healthy grass can have a small amount thatch. Some is good, more is not. Most lawns do have thatch, and in small amounts it’s kind of like the padding under a carpet, providing a resilient, springy surface to walk on. It is thick EXCESSIVE THATCH that gives this normal aspect of lawns a bad name.
Thatch is a layer under the growing grass you see, comprised of an intermingled layer of lawn clippings and other living and dead plant stems, leaves, and root matter that gather at the base of the grass, between the soil and green vegetation.
Thatch does not necessarily mean you will have issues – it’s more about HOW MUCH thatch is present. You only have a “thatch problem” if the thatch layer gets so thick so that water and air have trouble getting to grass roots.
EXCESSIVE THATCH comes about from practices that make the grass grow faster that soil organisms can break it down, or that reduce beneficial soil organisms such as earthworms, insects, and microscopic species. The practices that cause the type of overly-rapid growth that can lead to EXCESSIVE THATCH include over-fertilizing, over-watering, and/or causing soil compaction.
EXCESSIVE THATCH may:
- Prevent water, air, and nutrients from reaching the soil and grass plant’s root zone,
- Reduce tolerance to drought and temperature extremes
- Provide a protective environment for insect pests like webworm larvae, chinch bugs, and billbugs
- Provide an environment that encourages fungus disease
- Prevent some insecticides and herbicides from penetrating the soil, which makes them ineffective
- Obstruct overseeding
A thin ¼-½ inch layer of thatch actually can provide benefits like surface cushioning, greater tolerance to wear and tear, and better temperature moderation.
EXCESSIVE THATCH of 1 inch or more can, however, cause a host of lawn problems. Grass varieties that tend to produce thatch more slowly are fescues and perennial ryegrass, whereas grasses like zoysia, Bermuda, and bluegrass tend to produce more thatch.
The GOOD NEWS is that in most cases, people really don’t have an EXCESSIVE THATCH PROBLEM at all. How can you tell?
- If you mow frequently enough so as not to remove more than 1/3 of the leaf blade at a single mowing where you’re cutting less than 1 inch of the leaf blade, the clipping will disperse and and decompose with sunlight and moisture quite quickly …. LONG BEFORE they can accumulate and become “excessive thatch”
- If, on the other hand, you are not mowing regularly and end up cutting more than about 1 inch of the blade, it takes longer for these clippings to decompose and they can suffocate your lawn.
- Get a little hands on! Whenever you mow, take a minute to scout things out, like a Farmer does for their crops. Use your finger to dig down around the base of your grass plants. If all you find is bare dirt, then you do not have an excessive thatch problem. Check again a couple of days after you mow. The clippings you leave should be barely noticeable.
- If you wanted to measure the thickness of thatch (and again, healthy grass has thatch!), poke around the grass until you find the brown layer near the bottom of the grass blade. With your finger or a stick, poke a hole through the brown layer to the top of the soil, and measure the thickness of the thatch. If your thach layer is less than 1/2? thick, it’s not a problem, and you can leave the grass alone.
If you’re still a little skeptical about leaving your clippings on your lawn after mowing, Regional Turfgrass Experts at Purdue University explain:
Clipping removal is generally not recommended on most turfgrass areas. Clippings do not contribute to thatch because they are primarily water and break down quickly. Furthermore, returning clippings will recycle valuable nutrients to the soil thereby reducing fertilizer requirements. Clippings are not harmful if your mower spreads them evenly and if they are not thick enough to shade the grass below. Mulching mowers are recommended, but research suggests that mulching mowers increase clipping breakdown only slightly faster than conventional side-discharge mowers when used on cool-season turfgrasses. Catching clippings is labor and time intensive and should only be done if the clippings are used for mulch or compost.~ via Purdue University Turf Science Department of Agronomy Publication Ay-8-W, “Mowing, Dethatching, Aerifying Mowing, Dethatching, Aerifying and Rolling Turf and Rolling Turf”
Purdue’s experts also offer this advice:
Yard waste materials such as grass clippings, leaves, and yard trimmings make up approximately 10% (by volume) of the municipal waste stream, according to Indiana’s Department of Environmental Management. Yard waste can account for 50% or more of residential solid waste during the active growing season. Although this waste is biodegradable, landfills do not get the oxygen and water needed for breakdown. Landfills are constructed to prevent movement of air and moisture in order to protect the surrounding environment. These materials can be better put to use enhancing our gardens and landscapes.
Leaving grass clippings on the lawn rather than bagging for disposal is an excellent way to dramatically reduce yard waste. The amount of grass clippings generated from a given lawn varies, depending on the grass species, weather, fertilization program, and yard size. One estimate indicates that 5,000 square feet of lawn generates about 1 ton of clippings per year! Grass clippings left on the lawn are not harmful to the turf if it is mowed at the proper height and frequency. In fact, the clippings will return some nutrients back to the soil, reducing fertilizer requirements. Contrary to popular belief, grass clippings do not contribute to thatch buildup because they break down quite rapidly. Thatch is composed of dead, decomposing roots, and underground stems.~ via Purdue University Cooperative Extension Service, West Lafayette, IN, Publication ID-182-W, “Managing Yard Wastes: Clippings and Compost”
So, the RIGHT QUESTION to ask is, “Do I have an EXCESSIVE THATCH problem?” and the answer is often No, but proper assessment is the only way to tell for sure.
You can LEARN MORE, including how to DETHATCH if you need to, by clicking on the links blow
- Purdue University Turf Science Department of Agronomy Publication Ay-8-W, “Mowing, Dethatching, Aerifying Mowing, Dethatching, Aerifying and Rolling Turf and Rolling Turf”
- Purdue University Cooperative Extension Service, West Lafayette, IN, Publication ID-182-W, “Managing Yard Wastes: Clippings and Compost”
- Purdue’s Plant and Pest Diagnostic Laboratory Picture of the Week: Thatch Buildup in the Lawn
- Purdue University Turfgrass Specialists Maintenance Calendar for Indiana Lawns