You know how excess skin cells can build up, clogging pores and preventing moisture from reaching deeper dermis layers? The same can be said about excess thatch on your lawn; it keeps air, water, and nutrients from reaching turf roots. But what are the signs your lawn has excessive thatch?
To start, your thatch layer is greater than one-half inch thick, your lawn is made of thatch-prone turf, and it feels extra spongy underfoot. For details on these and a few more signals to look out for, keep reading.
But First, What Is Thatch?
That layer of organic matter composed of living, dead, and decaying grass stems, crowns, and roots is called thatch, and it naturally forms between the soil and your growing lawn blades. If the layer stays half an inch thick or thinner, it can be beneficial to your lawn, creating that soft feel underfoot, preventing weeds and disease, and insulating soil and keeping it hydrated.
Thick thatch, however — when the layer reaches a thickness greater than one-half inch — can adversely affect your lawn by inhibiting nutrients, water, air, and other soil amendments from reaching the soil and grass roots. Such density can even cause grass roots to grow within the thatch, making the roots more susceptible to stress like overwatering, drought, cold, pests, and diseases.
Sign 1: The Layer of Thatch Exceeds One-Half Inch
If the layer is thin (one-half inch or less), your lawn is in good shape and doesn’t need dethatching. More than one-half inch of thatch, though, can block sun, water, and other nutrients from reaching turf roots and cause roots to become shallow, taking up space within the thatch layer, rather than growing deep into the soil.
How to Test Thatch Thickness
To check your lawn’s layer of thatch, cut out a 2- to 3-inch segment of turf with a trowel or grass plugger, and measure the thickness of the existing thatch.
Sign 2: Your Lawn Is Comprised of Thatch-Prone Turf
If you’ve planted turf that spreads via stolons or rhizomes, most likely, your lawn will experience excessive thatch at least once a year, as this type is more prone to thatch than bunch-type grasses.
Why? Rhizomes or stolons take longer to break down during decomposition. Bunching grasses, on the other hand, spread via tillers, so there typically isn’t an abundance of stems.
Examples of thatch-prone turf types include:
- Creeping red fescue (cool-season grass)
- Bentgrass (cool-season grass)
- Kentucky bluegrass (cool-season grass)
- Bermudagrass (warm-season grass)
- St. Augustine Grass (warm-season grass)
- Centipedegrass (warm-season grass)
- Zoysiagrass (warm-season grass)
Sign 3: Your Lawn Is Suffering from Disease and/or Pests
Thick thatch provides an ample buffet for bugs to feed on and creates a desirable habitat for fungi and other diseases to thrive — think pests like grubs or chinch bugs or turfgrass diseases like brown patch or pythium blight. These can cause your grass to turn brown, wilt, and/or become excessively dry.
Note: Another signal you have thick thatch is if fungicides, pesticides, and herbicides aren’t working properly in your lawn. Often, these treatments can get stuck in the thatch, rather than making their way through the soil, and thus, cannot address the problems.
Sign 4: There Are Bare Spots on Your Lawn
Despite your best efforts to fertilize, overseed, and aerate, you may have a thatch problem if bare spots persist. Thick thatch can lead to bare spots simply because it blocks necessary nutrients from reaching turf roots. In turn, grass roots will start growing within the layer of thatch to better receive water, grass, air, and the like, which will predispose it to stress (and death) from drought, heat, and overwatering.
Sign 5: Your Lawn Feels Extra Spongy Underfoot
Healthy thatch (again, that’s thatch that’s half an inch or less) gives your grass a feeling of soft, bounciness underfoot. But if things start to feel overly squishy, it could signal your thatch is too thick.
When this happens, your lawn can hold on to too much water, making things (like lawn mowers) more apt to sink into the ground (e.g., your lawn mower won’t be level and can accidentally cut your lawn too short).
If your lawn shows any of these signs, check out our dethatching guide for solutions.
FAQ About Thatch
Do all types of grasses need dethatching?
Not exactly. Generally, warm-season grasses like Zoysia, St. Augustine, and Bermudagrass are the most prone to thatch, while bunch-type cool-season grasses like perennial ryegrass and tall fescue don’t typically need dethatching.
Note: Cool-season grasses that spread via rhizomes (e.g., Kentucky bluegrass and creeping red fescue) can be prone to excessive thatch; the stolons and rhizomes can pile up on lawns faster than microbes, earthworms, and such can decompose them.
Does aeration remove thatch?
Aeration won’t remove thatch from your lawn like dethatching will; however, it can help encourage the decomposition process, which will naturally keep excess thatch in check. It does this by removing plugs of soil from your lawn, resulting in increased movement of air and water, leading to better root health and an overall improved environment for decomposers to thrive.
Do liquid dethatchers work?
The reviews are mixed. Liquid dethatchers are made up of bacteria and enzymes that are supposed to break down thick thatch; basically, it’s like an added dose to the bacteria and enzymes that naturally occur in your soil. Some lawn care pros say it works, with the caveat that it must be applied multiple times and only to small problem areas. The best way to remove thatch is still with a dethatching machine or rake.
Hire A Pro To Care For Your Lawn
Letting your lawn grow a bit too long and cutting it more than one-third of its height can contribute to thick thatch. Stay on top of your mowing with help from a lawn care pro near you. Not only can they handle that yard task, but they can also fertilize, aerate, weed, and determine whether your lawn needs dethatching.
Main Photo Credit: pitrs / Adobe Stock
