What is dethatching?
Ok, so you want your lawn “dethatched” in the spring. Thatching, or dethatching, a lawn is another one of those vague terms used in our industry. Many of our customers, as well as our landscaping partners, consider “thatching” as a normal part of their early spring cleanup. They’re usually referring to the practice of running a tine rake attachment mounted on a commercial mower. This practice usually rakes up winter debris and causes matted down grass to be lifted to help “wake up” the lawn. This, basically, imitates the action of giving the lawn a good, stiff raking, with a leaf rake, to “fluff up” the matted grass blades and get rid of debris leftover from winter. Our version of dethatching a lawn is quite different from this. To explain this, let’s go over what thatch really is.
What is thatch?
Thatch, as defined by turf scientists, is not the dead, matted grass blades from the prior season. Instead, it’s actually the layer that lies between the grass blades and the soil. It is made up of old shoots and roots that are fibrous in nature and form a protective mat between the atmosphere and the root systems below. This mat forms over a period of years, as old roots and shoots die off and new ones grow. This forms a pretty tough layer, with the consistency of wool felt. A healthy lawn should have a thatch layer of about 1/2”. This is enough to insulate the roots from heat, drought, and other extremes in weather, but not so thick as to prevent water and nutrients from getting to them.
Why is thick thatch bad?
Unfortunately, sometimes this layer becomes so thick that it becomes detrimental to the turf. Excessive thatch hinders air, water, and nutrients from reaching the roots. Once this happens, the turf roots will start to compound the problem by growing upwards, into the thatch, because that’s where the water is trapped. Turf roots are pretty fibrous, and touch, by nature. Adding that to a thatch layer quickly thickens the thatch and weakens the grass. Think of it as a thick felt mat. It takes a lot of water to saturate and finally penetrate a thick felt mat. It also acts as excellent shelter for insects and diseases. Thick thatch can also prevent a lawn from recovering from drought, heat, and other damage. Once a thatch mat gets too thick, it usually requires some kind of mechanical methods to control and reduce it.
How do we control, and reduce, thatch?
Proper watering goes a long way toward not developing a thick thatch. Watering deeply, and infrequently, gives the roots all the water they need. The areas near the surface then have a chance to dry out regularly. The roots will grow downward, as they should, in their search for water.
When thatch becomes too thick there are a couple of mechanical methods to reduce and control it:
Core aeration - Core aeration is punching holes through the thatch and pulling up soil cores. This helps air, water, and nutrients to penetrate an otherwise suffocating layer of thatch. The soil cores also break down on the surface, which gets some soil spread out over the top of the lawn. This helps to further decompose some of the thatch. We have many customers that have us do this annually. This regular practice, monitoring soil pH, and proper watering will usually keep thatch under control
Dethatching - This is a more extreme method of thatch removal. When the thatch layer is so thick that it needs a little more than core aeration, we’ll recommend this service. It’s usually done in addition to core aerating. Most true mechanized dethatching machines (also sometimes called “power rakes”) have heavy gauge flailing blades that strike the thatch layer. This mechanically rips out part of the thatch layer. This usually results in a lot of plant material being ripped up (see photo in title)
When is the best time for a true dethatching?
While running a tine rake over a lawn is just fine for early spring, and calling it “thatching,” is OK, doing a true heavy dethatching in early spring is not a good idea. The grass is just waking up and hasn’t had a chance to develop new roots and shoots. It’s in a pretty delicate state. We’ve seen heavy dethatching, done with a power rake in early spring, rip a lawn to shreds!
Power dethatching should be done in the late summer or early fall. The lawn is mature and firmly rooted. It can withstand the beating that a power rake will give it. It may also be a little damaged from the summer heat, drought, insects, or diseases. Dethatching, in addition to helping control thatch, can also create a good seedbed for repairing that damage, along with core aeration. This is why we dethatch lawns only in the late summer and early fall, in concert with core aeration. This “1-2 punch” creates an excellent opportunity to get some seed down and help it heal during the fall “recovery” season.
Please reach out with any further questions.