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

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.

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

  1. breathofdeath says:

    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.

  2. Reacee says:

    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?

  3. Pingback: LUMPY BUMPY LAWNS: Rolling not a good idea for lawns | LawnSavers Blog

  4. S. Deshotels says:

    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.

  5. jeff says:

    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 says:

      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!

  6. Louise Rutland says:

    Hi. I would describe my lawn as undulating rather than bumpy as the areas of different heights are a few feet in area, but still severe enough to twist an ankle. It could not be fixed by suggestions I’ve read on here so needs a total overhaul.

    Given i don’t need a Wimbledon quality lawn my question is therefore whether to just dump a load of top soil over the existing grass, level and reseed or hire a rotovator or other machine to churn off the grass first?

    • Kyle Tobin says:

      if you are looking to completely renovate the lawn, I would first use a vegetation killer to ensure you kill off the offending species of grass, and then grade the lawn. Its always a great idea to add organic matter to the existing soil and work it in. BUT, please don’t use regular old topsoil and the mess of weed seed and weedy grass seeds that come with it- you’ll be worse off!

  7. Don says:

    A bumpy lawn has been a characteristic of my lawn for many years. It’s that way year-round. There’s no sign of bug problems as the grass growth is consistent across all of it and as long as it gets adequate water, it grows well and the roots seem deep in the soil (about 3″). The spoil is sandy loam – no clay. I normally mulch it when I mow& fertilize 2-3 times a yr.

    I’ve tried top-dressing it but the soil ends up in the thatch of the high spots (bumps) as much as in the low spots, so it’s still bumpy after all the raking to distribute the soil.

    Could it be just the different growth patterns of the grasses in my turf? I have re-seeded over the years with various seed (incl. tall fescue). Would it help to mow the lawn really low, to get to (lower) the thatch part of the higher bumps and then top-dress & seed? Or will it just grow back the same? I normally cut the grass quite high.

    • Kyle Tobin says:

      Tall Fescue will cause clumping as that is the style of its growth- this will promote further “bumps”.
      Do not scalp the lawn as that will not help.
      Different types of grass species is definitely part of the problem if they are not well interspersed.

      i would try a severe de-thatching and then power-seeding with topdressing and regular- frequent aeration.

  8. jim chambers says:

    I have large pine trees with roots that are coming to the surface causing dips and irregular lawn surface. How can I cover the roots and fill in dips? I have used sand in passed with a different lawn with clay like soil.. The soil with this lawn is gravelly. I don’t want to cut the roots, fearing I may kill the tree. Can you help? Thanks, Jim

    • Kyle Tobin says:

      Hi Jim,
      If you are trying to grow a lawn under the canopy of the trees, its really hard to do, and you’ll meet limited success. The best bet is to mulch out a foot or two past the drip line and create a uniform and neat mulch bed. (2-3 inches of mulch over a permeable landscape fabric).
      You’re right- cutting the roots wont help and will severely inure the tree. Other roots may surface anyway.
      Tree roots don’t take nicely to covering up their roots since you will limit air exchange- vital to a healthy tree. If you do try to cover, most literature says not to add more than 1-2 inches MAX.

    • Francis says:

      Try aerating and applying compost and sand. It may take a few seasons, but that should improve the soil texture

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