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Dethatch that Thatch

Last week we talked through how to aerate the soil beneath your turf grass to help water to infiltrate deeper into the soil and encourage deeper root growth. Step three of that process was to dethatch your grass if needed. This week we’ll take a closer look at that thatch and think through the dethatching process.

First, a reminder on what thatch is:Thatch - Soil and Root System

Thatch is a thin layer of living and dead stems, roots, and rhizomes between the green portions of turf grass (e.g. the blades) and the actual soil. A thin layer of thatch is beneficial (think of it like a tiny, self-sustaining layer of mulch) in helping limit weed germination and reduce water evaporation. It can, however, get too thick and prevent water, air, and nutrients from reaching the soil.

So when is thatch too thick? Generally you want the thatch layer to be less than half-an-inch thick. Some turf grass, such as tall fescue and perennial ryegrass, do not produce much thatch. Other grass types, such as Bermuda grass, rapidly build thick thatch layers. To check your thatch thickness, remove a soil core (and maybe gauge how deep water is infiltrating your soil while you’re at it) and measure the small, brown thatch layer between the grass blade and the soil surface. If it is over half-an-inch, dethatch.

Thatching RakeFor smaller spaces, a thatching rake (available at most home improvement stores) will do the trick. A thatching rake has vertical blades that dig into the turf, loosen the thatch layer, and slice it to destroy the network. You simply drag it across the turf grass like any rake and it will pull up the thatch layer.

For larger spaces, a vertical mower (or dethatcher) automates the process with a series of vertical blades that cut the thatch and pull it to the surface. While vertical mowers can be rented at most rental equipment centers, it may be more convenient to hire a professional if your space is too large. Vertical mowers have to be manually calibrated so that the blades cut just deep enough to go through your thatch but not into the soil.

In either method, the thatch layer will be pulled up and scattered across the surface of the grass as debris. This debris can be gathered and composted and will contribute organic matter and nutrients to improve the structure of heavy soils.

The best tip, though, is to prevent thatch from building up in the first place. There are two key tricks to help keep your thatch in line and, not surprisingly, both of them are good gardening practices.

  • Proper fertilization. Don’t over fertilize and avoid excessive amounts of nitrogen. Too much of either encourages the production and buildup of thatch.
  • Deeper watering. Avoid frequent and shallow irrigation. Thatch grows on the surface of the soil and the living parts don’t have deep roots, so all of the water and nutrients that builds up thatch comes from shallow sources. To the extent you’re able without overwatering, deeper watering will feed your turf grass without feeding thatch.

As always, I’m here to help. Let me know if you need to dethatch!

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