What are all those bumps on my lawn?

What are all those bumps on my lawn?

We get asked this question alot.  What are all these little bumps in my lawn?  If you have bumps in your lawn it’s generally a good thing, as it indicates earthworm activity in your soil.

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Earthworms chew their way through the soil and eliminate behind them.  The eliminations are called castings.  The castings are usually moist and look like little mud balls.  As the castings dry, it hardens and makes little mounds of dirt in amongst the turf.  If you flick off the top of the dirt mound you’ll usually find a small hole.  Night crawlers are the little guys that make the biggest mounds.  Generally, you can see holes up to 1/4″ after removing the casting mound.

It’s a good thing what they do in that they are helping aerate your soil.  This helps improve soil structure by relieving soil compaction, improving air circulation, moisture penetration and it also increases microbial activity, which in turn helps decompose thatch.  Without boring you will all the other compounding benefits, just know that worms are a good thing and any pesticides applied to your lawn will not effect them.

So what to do about all those bumps you say?  Well, the best way to approach it is to try not to put in too much effort.  You’ll always have earthworms and that’s a good thing.  So, by fertilizing your lawn and maintaining a good thick turf stand you help to mask the bumps in your lawn.  If your turf stand isn’t as dense as you would like it or you can see the castings without having to pull away the grass then you should seriously consider an over seeding service to sew in more grass seed to help thicken your lawn.  Having a good thick turf stand is beneficial in many ways.  The more intense approach would be to stop into your local hardware  or big box store and pickup a lawn dethatcher.  De thatching your lawn in the spring time is always recommended before the green shoots start to rise.  But, you can also do this at any time of the season.  A lawn dethatcher has metal tines that flick and scrape at the grass helping to remove dead decomposing grass.  It also can help break down those dirt castings and relieve some of the bumpiness.  It may take several passes to get enough of them to meet your satisfaction.

NEVER ROLL YOUR LAWN!!!  Rolling your lawn may seem to be a good idea in this case but it is definitely not.  Rolling your lawn compacts the soil making it extremely difficult for turf grass roots to grow and pull in the nutrients and moisture they need.  The only time we’d recommend rolling a lawn is just after you seeded a new area.  That would help drive the seeds into the soil.  But you wouldn’t be looking to compact the soil here so you would be using a light weight roller.  Something that wouldn’t do much for squishing the earthworm castings.

Taking the time to diagnose what is really going on with your lawn is the first step in protecting your investment for the long haul.

If you think you have some turf density issues and are currently on our regular lawn care program, GIVE US A CALL!   We’ll give you some recommendations as to what your lawn or soil needs to get the lawn you’ve been looking for.


  1. I have bumps all over my lawn. It is driving me crazy and hard to walk on the lawn in the summer. what do I do? How do I get rid of this? If this is good for my year as you say – why does it still look like crap?

    • I can understand your frustration. It’s really a pain to see all of this going on in your lawn. I wish there was a better solution for you but here is my take on it. If it is in fact night crawlers than the lumps of dirt you see will be at their peak in the spring time and possibly the fall. Soils right now are very moist if you are in the State of Maine. This means with each rainfall these little (or big) guys come to the surface. It is said that they do this to get more oxygen. When the moisture level in the soil reaches a high level they come up to breathe. It’s also said that they do this at night when it is raining to easily move to other areas easily due to the excess moisture. They are a good thing! But a pain in that they leave all these castings on the surface of your lawn. The castings help to decompose thatch because they bring the soil above the thatch layer of the lawn and in essence slowly churn the soil over time. This will slow as soon as the moisture levels in the lawns and the rains slow down. Since it’s spring time it’s just something that some folks that have high populations just have to deal with. My recommendation to you is to get a roller. I usually don’t advise this as it compacts the soil. However, if you have high populations of earthworms & night crawlers than it might be ok to fill it 1/2 full and run it around after a rainstorm. When you do that the castings will easily squish back or flatten. This will give you a more smooth surface and hopefully that will be enough for you. Beyond that you could try running a de thatcher rake over the lawn in an effort to flick over the casting mounds.

      Make sure you are fertilizing your lawn throughout the season. This will help create a thick dense turf stand. When you do this the castings will be masked by the grass. If your lawn is really thin then I’d recommend slice seeding the areas that are thin and then keeping the fertility up in the lawn.

      Hope that helps! Thanks for visiting!

  2. please get back to me does soil lump balls go away with alot of rain yes or no

    • Depends upon how much rain. But yes. Typically scat is the cause of these soil lumps. It’s the soil that passes through the bodies of worms. When they exit the soil in the evenings they will leave these scat mounds. They will go away with time. However, if you have an overabundance of worms you may never see the end of it.

  3. I also have the same problem, they are very hard to walk on. So if I am understanding this correct it is worms. So will more dirt in my lawn/yard help with the problem? Also will thatching help?


    • Since this is such a popular topic I’ll see if I can’t come up with another article to help people deal with it. I believe back in the day there some sketchy solutions for it. A quick idea would be to add several bird feeders to your property. Let me think on this one for a bit and do some research. If you are subscribed to our newsletter you’ll be sure to receive an update.


  4. Interesting articles!

  5. I have found 3 or 4 small mounds of dirt in my backyard and also 6 small holes in different areas of the yard. I noticed a big black with white stripe insect burrowing into one of the mounds at dusk. Can you please tell me what this insect is and what can I do to get rid of them.

    • It’s hard to tell what type of insect it is by your description alone. Do you have photos? Where are you located?

  6. Worms yes, but also larger creatures. My lawn has 12″ sunken areas that I believe are collapsed chipmunk dens. Mice, voles, moles, underground bee nests, and areas where skunks and racoons have dug out the bees. It’s a jungle out there. Also ant nests that I have killed off, and there is some other insect that borrows out of 1/4 inch holes in the spring. Nothing to do on the sunken areas but to put down clean dirt and reseed. Maybe dethatching and raking is good for the small lumps but if you trip on one of those sink holes while you’re raking you could break an ankle. And, when I ride the mower I usually leave a kidney out there.

    • HAHAH! Sorry about your kidneys! What part of the country are you located in?


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