How to Dethatch Your Lawn

Wondering if you need to dethatch your lawn? Have you lived in your house for years or bought a new-to-you home with an existing lawn? Grass cutting, watering, fertilizing, overseeding and weed removal are all part of the maintenance. Think of dethatching as another maintenance strategy.

People dethatch a lawn when they:

1. Plan to overseed an existing lawn and want to improve contact between seed and soil, or
2. Want to improve the health of the lawn and suspect thatch buildup may be a problem. Generally overseeding afterwards is necessary.

What Is Thatch?

Thatch is the buildup of plant material that collects where the grass meets the soil. Clippings from cutting your grass with the lawn mower are the most common contributor.

This material is beneficial when it feeds the roots of your grass plants. It only becomes a problem when it doesn’t break down fast enough. Plant material becomes a carpet that smothers the roots of the grass.

A one-inch carpet of thatch:

• Blocks water from penetrating into the ground and creates water runoff.
• Keeps nutrients from penetrating to feed the roots.
• Keeps grass seed from connecting with the soil and germinating properly to grow new plants.
• Provides an unstable rooting medium for new roots of existing grass plants. If roots try to grow in thatch instead of soil, they can dry out and die.
• May harbor harmful insects and plant diseases.

Signs of a Thatch Buildup Problem

• A small trowel doesn’t go into the ground easily.
• There’s a springy feel while walking on the lawn and it’s not caused by the soles of new sport shoes.
• During a significant rainfall water runs off instead of soaking in.

How to Find Out if You Need to Dethatch

Dig a section with a small trowel in several places in your lawn. Look at the layer of brownish mass of material sitting on top of the soil in each sample. Measure its thickness.

Time to make a decision.

Dethatch when:

You are overseeding and want to improve the seed to soil contact regardless of the thatch depth.

You want to improve the lawn's health and thatch is an inch or more.

Don't dethatch when:

You are not overseeding and it’s less than an inch. You can leave the thatch alone. Add some compost or a mixture of compost and soil into your lawn to help the thatch decompose. Rake the compost gently into the ground to spread it around.

Best Season to Dethatch

Best time to dethatch is early in the growing season. Find out what type of lawn grass you have and when it is actively growing. Fast-growing grass will recover quicker from the dethatching, overseeding and fertilizing.

Homeowners may hear their lawn type described in two ways. One is by the season in which they grow most quickly. The other is the type of root system the plant has for taking in nutrients and water.

Warm-season grasses grow quickly early to mid-summer. Cool-season grasses grow quickly in early fall.

Most Commonly Used Grasses for Lawns

Tools:

• Dethatching rake which has special tines for removal of plant material. This is usually for small areas.

• Dethatcher machine to rent or buy for large areas of the lawn.

• Markers to alert you to items that stand up from the ground's surface. Cutting the grass you remember them but concentrating on the dethatcher you might not. Things like low-ground pathway lights, sprinkler systems, tree stumps, large rocks that jut out or patches of uneven ground could damage the machine.

• Bag(s) of grass seed appropriate for your lawn size and type of grass for overseeding after thatch removal.

• Compost or other fertilizer.

How to Dethatch

Large Areas

Preparation

1. Cut grass with lawn mower to approximately two inches high. Using a bagger to collect the cuttings keeps from adding more material to the project.

2. Place markers for anything that may stick up from the ground such as path lights, sprinkler systems, rock outcroppings even high spots in your yard.

Use dethatching machine:

3. Start at one side of the area you want to dethatch. Make one pass over a strip just like you’re using a lawn mower.

4. Turn and do the next strip. Continue moving forward on each strip until finished.

Avoid going backwards with a thatching machine. Be careful of high spots in your yard as you can break the tines on the dethatcher.

Pulls up mostly dead plant material but some live grass may come up too.

5. Rake up thatch or use mower with a bag to collect the material.

6. Put the thatch in your compost pile where it will have more time to break down. Some cities have recycled yard waste programs. Drop off sites or curbside pickup may be available. Contact your city to find out how to recycle this yard waste material.

Lawn may look lower and thinner.

Now you’re ready to overseed and lightly fertilize following package instructions. Water the area thoroughly.

Small Areas

Follow steps 1 and 2.

Use dethatching rake:

Draw the rake over the ground one strip at a time, going deep enough to connect with the soil to pull up the dead material.

Continue strip by strip until you’ve finished the area.

Then follow steps 5 and 6.

Lawn Maintenance

Early in the growing season for your lawn type (as identified from the table above) check for thatch that might build up. Areas that get a lot of water or have high foot traffic may develop too much.

Add compost yearly to feed the grass and aid decomposition of old grass material. This might reduce the dethatch work to smaller areas that develop too much, too easily. Regular lawn maintenance that includes checking for and eliminating thatch buildup will improve the appearance and health of the lawn.

© 2018 Juli Seyfried