Lumpy-bumpy lawn – causes and fixes (How to repair a bumpy lawn)

by John and Kyle

One call we get a lot of in the Spring is “My lawn is really bumpy and uneven. Can you roll my lawn for me?” On the heavy clay soil we have in the GTA, nothing short of a steamroller can exert enough pressure to flatten a lawn by force. And if you did manage it, the soil would be so compact it would choke your grass to death anyway.

Lumps, bumps, holes and dips will show up on every lawn sooner or later. They happen for many different reasons throughout the year. Finding the right long-term-fix depends on the cause of the bump.
In Spring, bumps often appear as frozen, dense clay soil thaws unevenly. It  heaves and buckles like a bunched-up carpet.
Animals, both wild and pets sometimes dig holes in lawns. So do children at play, depressions can be created if people or animals walk on lawns that are too soft (like in the early spring or after long rains).  Some home gardening equipment can leave holes as well if misused.  Sometimes, just filling the disturbed soil back in and topping up with a good topsoil (hopefully weed-free), is a good repair for these holes. If they’re small the existing grass can grow over the hole. Larger spots should be seeded or even patched with sod.

If part of the lawn sinks and creates a depression the first thing to do is determine why. Removing the cause before correcting the effect is crucial. For any depression an inch or more deep, repair should involve removing the sod, correcting the cause of the sinking, and then back filling with new soil with enough extra to allow for settling. The removed sod can be put back in place if it is still in good shape, or replaced with new sod or seed. A shallow depression in the lawn – less than an inch deep – can be corrected gradually by sprinkling top dressing over it. Compost based mixes are good for this.

A very common problem is that people often perceive a lawn is bumpy when it has nothing to do with soil!  The lawn is made up of layers, for simplicity, lets say: the soil, roots, thatch, and the blades.  Thatch is the area just above the soil, that protects the roots.  It is normally about 1/4″-1″ in height of matted decomposing grass clippings and generally dying old grass plants that fade away as new plants are generated.  When you have a thin lawn or a disease or insect problem that is weakening an area (think Chinch bugs), the blades go first, then the thatch rapidly decomposes leaving bare soil. This bare area then erodes even deeper with rainfall, wind and activity. That leaves a depression when compared to the surrounding area of healthy lawn.  This is what we describe as the illusion of a bump.  Multiply that by several areas and voila! You feel like you have a bumpy lawn!

Bumps and rises also need to be diagnosed before correction. If caused by an object, it will need to be removed. If a bump is from burrowing animals they will have to be removed before the area can be smoothed. It may be possible to flatten smaller bumps by stepping on them.

The best way to correct and create a lawn that has very few bumps, is really quite simple- Ensure you have a green thick and healthy lawn. Your lawn care program should include  high-end nutrition components that thicken and fortify your grass plants, regular aeration to loosen the soil and lessen heaving, overseeeding to thicken the lawn and create a stronger more pest resistant lawn, as well as proactive insect control for Grubs and Chinch bugs.

Spring is the best AND worst time for people worried about lumpy lawn.  The ground is soft and grass grows quickly to cover any repairs, but snowmelt-saturated soil plus traffic on your lawn add up to new bumps.  You can read more in our April checklist. There are tips to avoiding creating ruts from lawn mower wheels when you mow the lawn in our lawn cutting tips section as well.

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LUMPY BUMPY LAWNS: Rolling not a good idea for lawns | LawnSavers Blog
June 23, 2014 at 9:09 am

{ 8 comments… read them below or add one }

alan April 22, 2012 at 5:26 pm

my lawn is very bumpy from large dew worms.What can I do?

breathofdeath August 6, 2012 at 10:13 pm

Then you got the “mother of all dew worms” invading your property. “Dew” worms appear after a heavy “dew” or a rain so they don’t drown. They eat and poop dirt so it passes right through them as they travel in the dirt. More like a condom with a hole at both ends. Or a thin skinned tube of spagetti. They don’t leave much of a hole behind besides these holes is what they call aeration. Better the worms do it rather than you running around the yard with a hay pitchfork making holes in the soil so the roots get air.
You could try watering less. Worms disappear if the soil is too dry. for them. I water once every 3 days and lawn is happy.

TEAM Bootcamp November 9, 2013 at 9:05 am

Great advice. Really helped. We have a 3 acre paddock that we use for training and it’s a nightmare.

Reacee May 19, 2014 at 12:02 am

My Husband and I are in the process of purchasing our
First home. A portion of the side lawn has a large
Hill-like mound/bump. It’s almost scary to look at. Can you
Offer any insight as to what the cause could be?

Kyle Tobin June 10, 2014 at 5:33 pm

Please send a picture of what you are seeing so we can better assist.
Here is a link to our submit a pic feature.

S. Deshotels July 3, 2014 at 3:34 pm

My lawn has hundreds of depressions, some with dead grass at the surface;others are are covered with grass (St. Augustine) Most are aprox. 8 inches in diameter. Some are much larger. Some are linear. There is no mound, dirt, or grass dug up around these depressions. They are deep enough to cause someone to trip or sprain/break an ankle. I do not see evidence of fungus or insect. The descriptions on voles or moles don’t seem to match. My husband fertilized twice early spring to get rid of buttonweed, which is still an issue. Could the possiblity of an uneven spread have caused this? What about the depressions with live grass, though? Any suggestions would be appreciated.

jeff January 18, 2015 at 1:26 pm

I have a yard that was put in 2012 sod. During last years summer it was dry so, we did not water often enough to keep the grass lush green. In the process, we had dry spots come up making the yard uneven little bumps while mowing. Should i re seed the yard? Or put soil down in those areas then seed it? Thank you, jeff

Kyle Tobin February 18, 2015 at 5:19 pm

Unfortunately Soil may not cure the problem. It depends on the depth of the depressions in your lawn. Keep it properly watered, fertilize well, Maintain it regularly with alternate mowing patterns, manage the weed and insect infestations and you will develop a thicker lawn with less (perceived) bumps. Let me know how it goes! Adding compost and seed after a good double aeration will definitely help!

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