How do you flatten a bumpy lawn?

Having a bumpy, uneven lawn can be frustrating. It looks messy, makes mowing difficult, and can even be a safety hazard. Thankfully, there are several effective methods you can use to flatten and level your lawn. Here we will explore the most common causes of a bumpy lawn and provide actionable tips to fix it.

Table of Contents

What Causes a Bumpy Lawn?

There are a few key culprits that lead to bumps and dips in your lawn:

Burrowing pests – Moles, gophers, and other burrowing critters can tunnel under your lawn, causing ridges, hills, and holes.

Thatch buildup – An excess of dead grass can create lumps and uneven areas. Thatch often builds up if grass clippings are not removed after mowing.
Compacted soil – Heavy foot traffic, machinery, or poor drainage can compress the soil over time, creating an uneven surface.
Improper grading – Incorrectly leveled or filled lawn areas during installation can lead to bumps and divots later on.

Identifying the cause of the bumps will allow you to focus your leveling efforts effectively.

Should I Dethatch or Aerate First?

If thatch buildup or compacted soil is the cause of your bumpy lawn, the first step is deciding whether to dethatch or aerate. Here are some tips:

If thatch is less than 1/2 inch thick, aerate first then dethatch a few weeks later.

If thatch is over 1/2 inch thick, dethatch first then aerate a few weeks later.
Dethatch in early fall or spring when the grass is actively growing to allow for faster recovery.
Aerate in early fall so the holes have time to fill in before winter or extreme summer heat.

Proper timing for dethatching and aerating is key – you want to disrupt the lawn as little as possible. Calling a professional lawn care company is a great option if you are unsure about tackling these projects yourself.

How to Dethatch a Lawn

Here are the basic steps for DIY lawn dethatching:

Mow the lawn short, around 1-2 inches high. Remove any existing grass clippings.

Use a dethatching rake, power rake, or vertical mower to remove debris and dead grass. Work slowly in different directions.
For thick thatch, make several passes over the lawn at different angles.
Sweep or rake up the pulled thatch so it can be disposed of or composted.

Consider sprinkling a thin layer of fresh topsoil to fill in holes and even the surface.
Allow the grass to fully recover for a few weeks before mowing again.

Dethatching is very labor intensive. Depending on the size of your lawn, renting a mechanical power rake can make the job much easier.

Dethatching Tips

Only dethatch in dry weather when the lawn can quickly recover.
Adjust the dethatching depth based on how thick the thatch layer is.
Make multiple light passes instead of trying to remove too much in one pass.

Dethatch in the spring or fall when temperatures are mild to avoid stressing the lawn.
Overseed with grass seed after dethatching to fill in bare spots.

Aerating a Lawn

Lawn aeration involves making small holes across the entire lawn to allow air, water and nutrients to reach the grass roots. Here are the steps:

Mow the lawn shorter than usual, around 1.5-2 inches high.
Use an aerator machine to punch holes across the lawn. The holes should be 2-3 inches deep.
Ideally holes should be spaced 2-6 inches apart, in a grid pattern.

Make repeated passes in different directions to cover the entire lawn.
Topdress the aerated lawn with a thin layer of compost or topsoil to fill in holes.
Water thoroughly to help decomposition of the plugs left behind.

Core aeration removes small plugs of soil rather than just pushing holes. This is more effective for deeply loosening compacted soil.

Lawn Aeration Tips

Time core aeration for early fall so the soil has time to settle before winter.
Water the lawn thoroughly a few days before aerating to make plug removal easier.

Use aeration shoes for small lawns – they attach spikes to your shoes!
Aerating in spring as temperatures rise can also work, just avoid extremely hot summer months.
Let grass clippings remain on the lawn to decompose and provide added nutrition.

Topdressing After Aeration

Topdressing is the process of adding a thin layer of material over the aerated lawn. This helps fill in holes and corrects minor uneven areas. Common topdressing materials include:

Compost – Nutrient-rich organic matter that breaks down quickly to improve soil texture.
Quality topsoil – Look for sandy loam topsoil for the best drainage.

Compost-topsoil mix – Combines the benefits of both materials.
Sand – Can be used alone or with other materials to break up heavy clay soil.

A light layer of 1/4 to 1/2 inch of topdressing is perfect after aerating. Here are some topdressing tips:

Use a drop spreader for even application over the entire lawn.
Water immediately after topdressing to wash particles into the aeration holes.
Wait at least 2 weeks before mowing to allow the grass blades to fully emerge.

Topdress overseeding for the best results at correcting bumps and depressions.

Other Ways to Level a Lawn

If dethatching and aerating fail to flatten significant dips or hills in your lawn, more intensive methods may be needed.

Raking and Overseeding

Use a heavy-duty steel garden rake to smooth very uneven areas of the lawn. Rake high spots down to fill in low spots. Then overseed with quality grass seed to thicken up the improved areas.

This works best for minor bumps and dips under 2 inches high/deep. Be careful not to damage healthy grass when raking.

Adding Topsoil

For deeper depressions or holes, adding fresh topsoil can effectively level the lawn. Follow these tips:

Add up to 2 inches of topsoil in thin layers, not all at once.

Use a straight board resting on the high points to check for dips as you add soil.
Gently tamp the added soil to prevent settling later on.
Water thoroughly and allow at least 2 weeks before mowing over newly filled areas.

Sodding Patches

Laying new sod is the quickest option for areas lower than 3 inches. Measure and cut pieces of high-quality sod to firmly fill each hole or dip.

The challenge is blending the edges of new and existing grass so the sod patches are not visible. Proper watering and mowing will help them blend more quickly.

Learning to Grade a Lawn

Completely re-grading a lawn is necessary if there are very high and low areas with more than a few inches of elevation difference. Re-grading evens out major bumps, hills and depressions across the entire lawn:

Mark the high and low points with stakes and string to map out the desired grade.
Rent a gasoline-powered rototiller and till up the entire lawn, removing weeds and old grass.
Rake smoothly from high points to low, creating a flat or slightly sloped grade.

Roll the newly graded area with a water-filled lawn roller to compact it.
Apply 2-3 inches of fresh topsoil if needed to reach the proper finish grade.
Seed the re-graded lawn or install new sod for instant results.

Grading requires experience to get the slope and elevation right. Consider hiring a professional landscaping company for complex grading projects.

Simple Lawn Leveling Projects

Not every bumpy lawn requires intensive aerating, dethatching or grading. For minor bumps and dips under 2 inches, there are simpler DIY projects you can tackle:

Sand Splash

This quick trick involves spreading a very thin layer of masonry sand over bumpy areas. Use a push broom to splash sand into the depressions. The sand will quickly work down into the holes to level the surface. Splash sand when the lawn is damp from dew or light rain.

Topdress With Compost

Compost offers an organic and nutrient-boosting alternative to sand. Use a thin 1/4 inch layer across uneven areas. Water thoroughly so the compost filters down to fill mini-divots and smooth bumps.

Lawn Rakes

For lawn bumps under 1 inch tall, a steel garden rake can smooth things out. Use the backside of the rake to gently tamp down any remaining high spots. Finish by overseeding to fill in uneven patches.

Maintaining a Flat Lawn

Leveling a lawn is only half the battle – proper ongoing maintenance is key to preventing bumps from returning:

Mow regularly at the proper height for your grass type. This prevents soil compaction from heavy mowers.
Leave grass clippings on the lawn to decompose and provide nutrients.
Water deeply and infrequently to encourage deep root growth.

Dethatch and aerate every 1-3 years to prevent thatch buildup.
Overseed to fill in thin or patchy areas that can become bumpy.
Re-grade significant dips, hills or holes as needed to keep a flat profile.

Lawn Care Calendar

Follow this monthly lawn care guide to maintain a smooth, properly graded lawn:

Month	Care Task
January	Inspect lawn for pooling water or ice, indicating improper grading
February	Start planning spring overseeding or leveling projects
March	Begin dethatching lawn as weather warms up
April	Core aerate lawn and topdress with compost
May	Overseed bare or thinning patches
June	Fill any holes or dips with fresh topsoil
July	Deep water twice weekly to prevent soil drying and compacting
August	Mow more frequently as grass growth peaks
September	Grade significant bumps and dips
October	Seed, sod or re-grade damaged areas before winter
November	Final mow and leaf cleanup before dormancy
December	Keep leaves off lawn to prevent smothering grass

When to Call a Professional

While many lawn bumps and dips can be smoothed out with DIY projects, it’s smart to have professionals tackle major grading or drainage issues. Seek professional help for:

Slopes or embankments steeper than around 4 feet of rise per 10 feet of run.

Drainage problems causing chronic wet spots or washouts.
Larger lawn depressions or mounds exceeding 3 inches.
Significantly unlevel lawn areas over 500-1000 sq ft.

Re-grading projects requiring specialized equipment.

A reputable landscaping company can assess your lawn’s grading and drainage and recommend the right solution. Many companies also offer routine lawn aerating, overseeding and leveling services.

Conclusion

Smoothing a bumpy, uneven lawn takes work – but is very doable as a DIY project if you take it step-by-step. The keys are identifying the source of the bumps, thoroughly dethatching and aerating, topdressing low spots, and proper ongoing lawn maintenance. Pay attention to proper timing for lawn care tasks and don’t try to remove too much material all at once. For major grading issues or rush projects, hire a professional landscaping company to get your lawn smooth, green and gorgeous in no time.