Scarifying a lawn: how to do it right

Arne Schätzle

Should I scarify, “yes” or “no”? This is a question many amateur gardeners have to answer each year. And how often should I use the scarifier? We explain how scarifying works, how your lawn will benefit from scarifying once or twice a year – and why scarifying might be a bad idea.

The scarified turf is clearly visible behind a scarifier.
© Getty Images / iStockphoto

In this article

How does scarifying work?

A scarifier scars the turf of the lawn, loosening mulch, thatch and moss, which can then be removed with a rake. This is good for the grass roots, helps aerate the lawn and stimulates growth. Various models of scarifier are available, whether electric, gasoline or hand-operated (see below). Alternatively, a scarifier can also be rented from a specialist dealer or DIY store.

Your checklist: what you need for scarifying

  • Scarifier
  • Fertilizer (at least two weeks before scarifying)
  • A rake to remove lawn thatch and other residues from the surface
  • Lawn seed, to reseed bare patches
  • Building sand to loosen up the soil (for heavy, loamy soil)

Advantages of scarifying

Scarifying the lawn is worthwhile for a number of reasons:

  • It frees the soil from moss and thatch
  • It loosens up the soil
  • It helps aerate the soil
  • It makes the lawn more resilient
  • It ensures that rainwater can drain away easily

Disadvantages of scarifying

On the other hand, there are several disadvantages to take into account:

  • Scarified areas need a lot of water, otherwise they dry out quickly
  • Scratching the turf stresses the lawn
  • The lawn will take time to recover from the operation
  • Scarifying results in bare patches, which are often invaded by weeds
  • Scarifying affects the soil life under the turf, as it completely removes the thatch on which bacteria, fungi, millipedes and earthworms feed.

Scarifying: how to maintain your lawn properly

Why should you scarify your lawn at all? Clover, thatch or waterlogging – here’s how to maintain your lawn properly:

1. Grasses, clover and herbs

The uppermost layer of soil, called the turf, is interspersed with grasses, clover and various types of herbs. The more this happens, the fewer nutrients, and the less light and oxygen, reach the lawn roots.

2. Thatch

Due to the vegetation cycle of plants, dead parts remain on the lawn – this can lead to accumulation of something known as thatch. The types of lawn that are most susceptible to thatch are heavy, loamy soils and shady lawns.

3. Lawn cuttings

When you mow the lawn, not all the cuttings always end up in the lawn mower. A few stalks may remain lying on the lawn. They will absorb light and oxygen – which then won’t be able to reach the grass itself underneath.

4. Waterlogging

If the turf in your garden is clogged, less water will enter the soil and get to the roots of the grass – and waterlogging will occur. This can also be remedied by scarifying, so that any excess water will seep back into the soil unhindered.

5. Suffocation

When you use a scarifier, you scratch the turf by making vertical cuts, loosening the lawn as a result. This improves soil aeration and provides the grass with a better oxygen supply right down to the roots.

A lawn with incised turf after scarifying.

When scarifying, move the machine length- and widthwise across the lawn to create a checkerboard pattern.

Scarifying a lawn: what sort of device is best?

Different versions of scarifier are available: electric, gasoline or manual. But which scarifier is most suitable for you?

Electric scarifiers have the disadvantage that the power cable can keep getting in the way as you work on the lawn. In small gardens, this is not too much of a problem, as you only need to use a scarifier twice a year at the most. It can still be a good idea to opt for a battery-powered scarifier, which frees you from the annoying cable.

Some electric scarifiers are very light and don’t apply sufficient pressure on hard terrain to allow the blades to penetrate the turf. In this case, you should weigh down the appliance with something heavy, such as a bag of potting soil.

Gasoline scarifiers are heavier simply because of the engine, so you don’t need to weigh down these models to be sure that the blades will cut deep enough into the grass.

You don’t have to watch out for the power cable either, but gasoline scarifiers are considerably more expensive: you can get a good model in shops from around 400 francs. You can purchase an electric scarifier with a power cable for as little as 100 francs, while battery-powered models are priced roughly in-between (approx. 200 francs).

There are also inexpensive hand scarifiers available for around 60 francs. These models are only suitable for small lawns that are not suffering too much from moss and thatch. This is because it’s hard work using a hand scarifier – the task can be very strenuous, especially on hard ground.

Scarifying: here’s how to do it

Step 1: choose the right time

There are a number of things to consider for scarifying to be really effective. The most important thing is to choose the right time of year, because if you start work too early, the lawn may still be too weak from the winter.

Temperatures should not drop below 5 degrees at night. Hours of sunshine and temperatures above 15 degrees during the day help the lawn to grow. Many gardeners start scarifying in May at the latest, when conditions are usually ideal.

But even later in the year, the weather can still be just right. And if you clear the lawn of moss and thatch before the winter, it will be easier for it to absorb nutrients during the lean season. October is the most appropriate month for scarifying. Any later than that, the risk is too great that the lawn will not recover before winter sets in. The only period to avoid is high summer, when the lawn is already under enough strain.

Scarifying twice a year can be useful if the soil and lawn have been neglected for a long period of time. For example, if a property – including the garden – has remained empty for a while before being sold. In this case, you will probably need to use the scarifier several times to remove dead grass, old leaves, leftover cuttings and moss.

A pile of thatch can be seen in front of a rake.

After scarifying, remove the loosened thatch with a rake.

Step 2: clear the lawn

To prepare for scarifying, start by clearing the lawn properly. Look for leaves, twigs and pine cones – and gather everything up. You should also remove decorative objects or garden furniture from your lawn before scarifying. This will ensure that you can scarify the entire lawn without any further effort.

Step 3: fertilize the lawn

If the lawn is still weak after winter, important nutrients such as nitrogen, phosphorus, potassium and magnesium can be put back in the lawn and the soil by fertilization. This will allow you to provide the lawn plants with the nutrients they need to make your lawn strong enough to grow and spread again after scarifying. Ideally you should fertilize in February or March, or at the latest two weeks before scarifying.

Step 4: cut the grass

You should mow your lawn shortly before scarifying. Cut the grass to a height of two centimeters – to give the grass growth stimulus.

Step 5: scarifying the lawn

The lawn should be dry for scarifying. Adjust the scarifying height on the machine so that the blades score the turf to a depth of about two to three millimeters. Hold the device briefly over the area without staying in one place for too long, otherwise the turf will be cut too hard and become damaged. Move the machine length- and widthwise across the lawn to create a checkerboard pattern.

Several blades can be seen on a spindle. These blades piercee the ground during scarifying.

The scarifier cuts two to three millimeters into the turf with its blades to remove thatch and weeds.

Step 6: rake after scarifying

Thoroughly rake the loosened thatch off the lawn. Bare patches will usually be produced in the process, so it is best to repair these areas by sowing fresh lawn seeds immediately after scarifying.

Sprinkling sand over the grass after scarifying is good for heavy, clayey soils: when you have finished scarifying, shake a layer of building sand about two centimeters thick over the lawn in your garden. The sand improves the aeration and water permeability of the soil.

More tips

  • For some amateur gardeners, fertilization and regular mowing are enough to keep the lawn in good condition. If the soil is loose and the area gets enough sunlight and water, scarifying may not be necessary.
  • Watering softens the upper layer of soil, which means that any moss rooted in it will be easier to pull out. However, the soil should be dry again for the actual scarifying process.
  • You should avoid using a scarifier on young lawns for the time being. If the grass is not firmly rooted enough, you will not only pull thatch and moss out of the ground, but also the grass itself.
  • You can walk on the lawn again immediately after scarifying. However, in order to give the stressed lawn time to recover, it’s best not to make heavy use of the lawn for a few days.
  • Even rolled turf is not immune to moss and thatch. Although it looks perfect to start off with, scarifying can be useful from the second year onwards. However, you should wait until then so that the turf is firmly rooted.
  • As a rule, scarifiers do not reach right up to borders and walls. This leaves a strip of lawn about ten centimeters wide, which you have to work on by hand.

Conclusion: scarify your lawn to ensure a vigorous, dense carpet of grass

Whether and how often you scarify your lawn depends on a number of factors: what is the nutrient content of the soil? Does it get much sun or does it tend to remain in the shade? Could the soil be over acidified? Or is it heavy and clayey?

Scarifying is a vital part of your year-round lawn care program, which should also include regular watering as well as targeted fertilization. Keep a constant eye on your lawn to determine what care it needs at any given time. Then there will be nothing stopping you from having a magnificent, lush green lawn.

You will find further helpful information in our main overview article on the subject of lawns.

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