You should scarify your lawn 1 to 2 times per year, depending on your grass type and the thickness of the thatch layer. Lawns that have not been scarified recently may need two scarifications in the same year to return the grass to health. If the lawn has been maintained or does not have a thick thatch layer, you can perform one annual scarification to keep the grass healthy. Measure the thickness of the thatch on your lawn in spring and again in fall. If the thatch is greater than ½-inch (13 mm) thick, scarification is necessary. If the thatch is ½-inch or less thick, you don’t need to scarify.
Why Do You Need to Scarify Your Lawn?
Scarifying your lawn is essential to remove excess thatch buildup from your lawn and prevent grass diseases. Thatch is the layer of dead material that collects on top of the soil, beneath your growing grass. If it is allowed to grow too thick, this thatch layer can block water, air, and nutrients from reaching the soil to feed plant roots. Fungus can also breed in the slowly decomposing thatch layer, which can result in fungal diseases that kill your grass.
- Scarifying removes excess thatch from your lawn.
- If excess thatch is allowed to remain, it robs moisture and nutrients from the soil and can harbor fungal diseases.
- Grass cultivars developed for lawns produce thatch faster than normal, since thatch allows these grasses to be grown as sod.
Unfortunately, we cannot always rely on nature to break down the thatch layer on its own. Several species of lawn grass have been bred to produce more thatch, since thatch helps grass form sod. The more quickly a grass type forms thatch, the easier it is to grow it and sell it as sod. Since most lawns start out as grass on sod farms, the grass in your yard is likely to produce a thick layer of thatch quickly.
Do All Lawns Need to be Scarified?
Some lawns do not need to be scarified at all. You only need to scarify your lawn if the grass produces a thatch layer that is more than ½-inch (13 mm) thick. Several species of grass produce little to no thatch, which eliminates the need for scarification altogether. Other species produce large amounts of thatch. Thatch-producing grass types benefit from scarification 1–2 times each year.
- Some lawns do not need scarification, or only need it very rarely.
- Other lawns require scarification 1–2 times per year.
- Whether or not your lawn needs scarification depends on the thickness of the thatch layer.
- Some grass types form thatch layers far more quickly than others.
Thatch is made up primarily of grass stems, which decompose very slowly. Some grasses produce very few stems, while others produce large stems and runners that form tough thatch. Whether or not you need to scarify depends entirely on the conditions in your lawn.
How Do You Know If Your Lawn Needs Scarifying?
To determine if your lawn needs to be scarified, use a small garden shovel to dig up a section of grass 2 inches (5 cm) square and 4 inches (10 cm) deep. Remove this plug of soil and grass from your yard. Then, use a ruler to measure the thatch layer. This is the compressed layer of brown or yellow dead grass that forms between the soil and the green grass. If the thatch layer is thicker than ½-inch (13 mm), then your lawn needs to be scarified.
- Use a small hand shovel to dig up a plug of grass and soil from your yard.
- The soil plug should be 2 inches square (5 cm) and 4 inches deep (10 cm).
- Measure the thatch layer of the lawn plug.
- The thatch layer is the brown/yellow material between the green grass and the soil.
- If the thatch is more than ½-inch (13 mm) thick, your lawn needs to be scarified.
Once you’ve finished measuring the thatch layer, you can put the lawn plug back into place in your yard. Then—depending on how thick the thatch layer is—you can start planning your scarification. It’s a good idea to check your thatch layer’s thickness in this way twice per year—in spring and fall. Since thatch thickness can vary throughout your yard, take a sample from a sunny area. Or, you can take multiple samples to see if thatch is thicker in certain areas.
What Month Should You Scarify Your Lawn?
April is the best month for spring lawn scarification in most regions, including the UK, as well as the Northeastern and Midwestern United States. In warmer climates, such as Australia and the Southern and Western US, it is best to scarify in March. Once the weather is starting to warm up and your grass has begun its spring growth, it’s the ideal time to scarify your lawn.
- March: is the best time for spring scarification in warm regions, such as Australia and the warm zones of the US.
- April: is the best time for spring scarification in cool regions of the US, as well as the UK.
- September: is a great time for fall scarification in cooler regions.
- October: is the best time for fall scarification in warm areas.
If you are scarifying your lawn in fall, do so in September in the UK and cool regions of the US. In warmer areas, you can delay scarification until October. The key to fall scarification is to begin once peak summer temperatures have ended. Once temperatures cool off from summer highs, your grass will experience a growth boost. This is a great time to scarify, since the fall growth spurt will help your grass recover from the stress of scarification.
Can You Scarify a Lawn Too Much?
You can damage your lawn by scarifying too much. Grass roots and stems can be heavily damaged by too-aggressive or too-frequent scarification. This can harm or even kill some of the grass in your lawn. Scarifying too often also removes the thatch layer completely. This can cause soil to dry out too quickly, which leads to a drought-stricken lawn.
- Heavy scarification can kill sections of grass.
- A lawn that has been scarified too heavily is prone to overly dry soil.
- If you scarify your lawn aggressively, you run the risk of removing the insulative layer of thatch your grass needs.
Although a thatch layer thicker than ½-inch (13 mm) is likely to cause lawn diseases, a thatch layer ⅛–½ inch thick (3–13 mm) provides benefits for the soil. In addition to helping retain soil moisture, a healthy thatch layer insulates the soil surface against temperature changes. This prevents grass roots from being overheated or frozen.
How Often Should You Use a Lawn Scarifier?
If you are wondering whether or not your lawn needs to be scarified, remember these key facts:
- Most lawns benefit from scarification 1–2 times per year.
- Some lawns need little or no scarification.
- Whether or not your lawn needs to be scarified depends on the thickness of the thatch layer.
- Dig up a small section of your lawn and measure the thatch layer with a ruler—if it’s more than ½-inch (13 mm) thick, your lawn needs to be scarified.
- It is best to scarify your lawn in spring or fall.
- In spring, scarify your lawn in March or April.
- In the fall, scarify your lawn between September and October.
- Avoid scarifying your lawn in the summer months as well as during the winter.
Light scarification will remove excess thatch without harming your lawn. Remember, you don’t want to remove all the thatch. A thin layer helps protect the soil and grass roots. Regular scarification leads to a greener, healthier lawn with a lower risk of grass rust and other fungal diseases.