What causes a bumpy lawn?
Before you start levelling your lawn, it’s important to understand what caused the exisiting grass to become uneven in the first place.
Once you know the cause, you can take steps to prevent it from happening again. If you find an issue such as a leaky pipe or a grub infestation, then make sure to deal with this before you fix the lawn. If you don’t, the bumps and low areas are very likely to reappear.
Here are some of the most common causes of a bumpy and uneven lawn.
Children and pets
Children or pets running around your yard puts pressure on the grass and can lead to low areas forming.
When the soil is softer, such as after watering or rain, it’s more susceptible to pressure and easier for depressions to form.
Burrowing creatures such as moles can create small holes and mounds in your lawn that will become a problem if there’s too many of them.
Moles love eating grubs. If you have lots of moles burrowing in your garden this could be a sign of a grub infestation.
Insect infestations themselves can lead to uneven lawns as they create patchy thin areas of grass. Exposed soil erodes faster than soil protected by a thick turf, so bare patches can quickly turn into a low-lying area.
Over fertilization of lawns can also lead to patches and therefore low spots.
Nightcrawlers are giant earthworms and are very beneficial for your soil. Their presence is a good sign that you have a healthy turf. However, if they’re present in large numbers, they can cause your lawn to become uneven and lumpy.
As nightcrawlers move through your soil, they deposit their castings on the surface of your lawn, creating small lumps. Their castings are an excellent fertilizer and full of nutrients like potassium and phosphorus, but the bumps can become a nuisance.
Settling is the term for general movements within your soil that over time can cause the surface to become uneven.
Clay soil is particularly prone to bumpiness. The repeated cycles of freezing and thawing that clay soil experiences over the winter months leads to a lot of upheaval within the soil. This can create a rough surface when the ground thaws in the spring.
Accelerated settling can happen when big logs that were buried in the soil decay, or rocks get moved around deep in the soil.
Leaking pipes and broken water sprinklers can cause soil erosion that results in low spots in your lawn.
If you see dips in areas you know there are pipes, it’s worth checking them for any leaks.
If there are parts of your lawn that get waterlogged when it rains, over time this will damage the turf and lead to an uneven lawn.
How to fix a bumpy lawn?
The best way to fix a bumpy lawn depends on the size of bumps and low areas you’re dealing with. You can deal with smaller bumps by top dressing your lawn. Larger bumps require you to remove the turf and level the soil underneath before replacing the turf or reseeding the patch.
How to smooth a bumpy lawn with top dressing
You can use top dressing to sort out lawns with smaller bumps and shallow dips around an inch deep. If you have bumps larger than this, then scroll down to the next section on how to smooth an uneven lawn by removing the turf.
Some people choose to make do with the tools they have rather than invest in a new leveling rake. But we definitely recommend getting a leveling rake. The leveler makes it really easy to get the lawn smooth and work the topsoil into the grass without damaging any of the blades.
Step 1: Mow the lawn as short as possible
Set your lawn mower to its lowest setting and mow the lawn. Having the grass as short as possible will help you see exactly where all the bumps and depressions are.
Step 2: Dethatch and aerate if needed
If you haven’t dethatched or aerated your lawn in a while, then this is the perfect time to do it.
We recommend dethatching when the layer of thatch (organic debris) in your yard is over an inch thick. When the thatch gets too thick it starts to prevent water and nutrients from reaching the soil.
We used this dethatching rake to remove thatch from our lawn and were very impressed with how easy it was. The rake’s made in the USA, so it has a high-quality build and a low carbon footprint. If you have a bigger lawn, then it’s probably best to use an electric dethatcher. The one from GreenWorks will get the job done in half the time a rake would, and with a lot less effort.
We advise aerating your lawn at least once a year if you have clay soil or a garden that gets a lot of footfall. For sandy soil types we suggest aerating at least once every three years.
Aerating helps loosen your soil and make sure that water and nutrients can penetrate deep into the root zone.
We recommend this core aerating tool because it removes soil from the ground rather than creating pathways by compacting the soil around the pathway. If you want to kill two birds with one stone, you can get some aerator shoes to wear while you’re mowing the lawn.
Step 3: Prepare your topsoil mixture of sand, soil and compost
Compost is the best material to use because it adds beneficial nutrients to your soil as well as filling in any holes. However, you’ll want to use high-quality compost that’s free of weed seeds. This can be expensive if you don’t make your own.
Most top dressing mixtures end up being a blend of compost, sand and soil because this is more cost-effective than just using compost. Sand is good to use if you have heavy clay soil. It will improve the structure of the soil and help with any drainage problems too.
When picking a soil to use, stick with something that has a similar structure to your current soil.
Step 4: Sprinkle the topsoil over your lawn and spread it evenly
Dump your top dressing mixture over any problem areas and spread it around using your leveling rake until the lawn is filled out and even. The rake will break up any clumps and remove any rocks to make sure the coverage is completely level.
Unfortunately, you can’t use a spreader to distribute the compost mixture, so you’ll have to get inventive.
Apply no more than ½ an inch at a time to make sure that the grass doesn’t get smothered and can grow through. If you need more than 1/2 an inch to correct your lawn, then it’s best to apply several layers of topdressing over a few months rather than do one thick coating.
Step 5: Work the mixture into the grass
Once you’re sure the topsoil is as level as you can get it, go over it a few more times with the levelling rake to really work the top dressing down into the existing grass.
If the grass is covered, then it’ll struggle to grow, so you want to make sure it’s poking through. The deeper you can encourage the topsoil to sit the better.
Some people like to walk over the topdressing a few times to make sure it’s secure. Compacting it lightly like this can help if you live somewhere windy and are worried about the mixture being blown away.
Step 6: Water the lawn
If you have any bare spots of grass, now is the perfect time to overseed them. We have a great article explaining exactly how to overseed a lawn, so if you need some tips on how to do it, make sure to check it out.
If not, then you can just water your lawn like normal. This will help the topsoil settle.
Step 7: Check on your lawn after a week or two and repeat if necessary
Levelling a lawn is a gradual process. After your topsoil layer has had time to settle fully, you might notice that the more significant dips are still noticeable and need another application.
This is fine, just repeat the process above, and eventually, your lawn will be flat as a pancake!
How to smooth an uneven lawn by removing the turf
For larger bumps, the process is a bit more involved. It’s sort of like operating on your lawn. You need to remove the turf, level the ground underneath and then replace the turf.
Step 1: Mow the lawn as short as possible
It’s a good idea to mow your grass before attempting any leveling so you can get a better idea of where the bumps and shallow areas are.
If the lawn feels dry, you should also water it a few days before you do the levelling to make sure the soil is soft enough to work with.
With your flat shovel or lawn edger cut a two-inch deep line around the bump or depression you’re trying to fix. Keep your tool vertical so the cuts are straight and clean. This will help minimize any root damage. Slicing a cross shape in the middle of the bump will make it easier to remove the turf.
Once you’ve made the cuts, slide your shovel underneath and remove the piece of turf. Try to keep the underside of the turf even if you plan on putting it back. If your soil is too dry, you’ll find it very hard to remove the turf evenly because the ground will start crumbling.
Step 3: Fill the hole or reduce the bump
If you’re fixing a sunken area, then fill the hole with soil until it’s high enough for the turf to be level with the lawn when you replace it.
As you’re filling the gap, make sure to pat the soil down and water it as you go. This will help to reduce any sinking after you put the turf back on.
To level a bump simply remove the excess soil from the turf before you replace it. Or you can dig a deeper hole if you think removing soil from the turf will result in root damage.
Step 4: Replace the turf and water
When the ground is level, replace the piece of turf you removed, tamp it down, and fill any gaps in the cuts you made with some soil mixture.
How to fix a bumpy lawn with unhealthy turf
If your grass is really patchy or has low areas that are over 2 inches deep, then the best thing to do is fill the holes straight away with soil and then reseed.
There’s no need to remove the existing grass if it’s not in good health because you don’t want to put back unhealthy turf.
When filling the hole, make sure to compact and water the soil as you go. If you don’t compact as you go, the new filling will compact naturally leading to another, albeit smaller, depression.
Once you’ve filled the hole you can then seed the new lawn.
Depending on how much excess turf you have, it may be worth considering a dumpster rental.
Should I roll my lawn?
Lawn rolling might seem like an easy way to fix a lumpy lawn, but we don’t recommend it in most situations. Sports pitches are routinely rolled to create a firm surface, but it’s generally a bad idea to roll a home lawn. Sports pitches need a lot of extra care because of the impact rolling has on the soil.
When you roll your lawn, you risk compacting the soil. Rolling squeezes all the pockets of air out of the ground, which creates an environment where it’s difficult for grass to grow. It’s harder for water and nutrients to penetrate compacted soil and reach the roots of your grass, meaning the grass can struggle to get what it needs to survive. This can eventually lead to wilting brown grass which isn’t a good look, even if the lawn is perfectly flat!
Sandy soils can withstand rolling much better than clay soils, as their structure means compaction is less of an issue. If you have a sandy soil type, you can consider rolling if you take these steps to protect the soil:
- Roll the lawn when it’s damp but not wet. If the soil is too moist, it’s more likely to compact. If it’s too dry, then the rolling won’t have any effect
- Use a lightweight roller
- Roll in the spring when the grassroots are in active growth
- Only roll your lawn if you have bumps smaller than 1-2 inches, such as those caused by worm castings or mild frost heaving
A lawn roller only flattens the first few inches of soil, so will only work on lawns with minor problems. If you have bumps larger than 1-2 inches, rolling will not help regardless of what soil type you have. You can also use a roller to firm up any top dressing you lay after seeding.
If you do decide to roll your lawn, we recommend this lawn roller from Brinly. It comes with an empty drum that you can fill with water so you can adjust the weight of it to suit your needs. The high-quality construction makes the roller very durable.