How to plant grass seed on hard dirt

When we first bought the house, we wondered how to plant grass seed on hard dirt. We tried everything! Some things worked, and some definitely didn’t. Here’s how we finally had success.

To plant grass seed on hard dirt, fix the hard dirt before planting the grass seed. No amount of TLC after planting will make up for poor soil prep. You need to get air and organic matter into the root zone soil before seeding the lawn. Enrich the soil, and THEN plant your grass seed.

This was not the quick-and-easy solution we were first looking for, but it has totally changed the way we think about our lawn. Read on for more about how to grow a lawn on less-than-perfect soil.

The basics to plant a lawn on hard soil

We learned pretty quickly that dealing with the hard soil is a better option in the long run.

Hard dirt can occur when the soil particles are very small, as in heavy clay soil. Lawn soil can also be hard because it has been compacted over time. Soil out in nature doesn’t get too much foot traffic.

The absence of heavy traffic allows air to exist in some of the void space between soil particles. Grassroots need this air! So, compact soil that doesn’t have much air available isn’t going to be the best for grass roots and turf.

Step 1: Do a lawn soil test

Step One is to get a soil analysis done. Soil tests can tell you how much clay, silt, sand, and organic matter your soil contains. They can also give insight into which nutrients might be missing. Get a lab soil test done – it is so worth it! If you’re not convinced, read this article about why soil tests matter.

You can even get your soil tested for compaction, but this is honestly a bit far for a home garden. I used to test soil for compaction on big construction sites (where compaction is desired!). These types of soil compaction tests are fascinating but aren’t really designed for home gardens or the organic matter that they (hopefully) contain.

In most residential lawn cases, hard dirt is caused by high clay content or by soil compaction. A soil test will tell you if you have awful heavy clay. It will tell you if perhaps your soil has less organic matter than you hoped. Or maybe your lawn used to be a gravel driveway. It’s hard to grow healthy grass on an unknown growing medium.

Key point – get a soil test done at a laboratory (I like SoilKit Soil Tests). The results may surprise you!

Step 2: Core aerate the existing lawn soil

Dirt becomes hard when air pockets get squished out of it. Perhaps the air pockets were squished out by glaciers thousands of years ago. Or maybe a car drove over the lawn area. Whatever the cause, compacted soil does not have a nice mix of minerals, air, and water.

We need to get some void space back into the soil to hold air and water. The roots of grass plants need direct access to both air and water.

hard dirt = no space = no air/water = sad plants

One way to re-introduce air into the soil is with a core aerator. A core aerator is a machine that pulls out little plugs of dirt, leaving small holes of air in the soil. The machine is about the size of a lawnmower and is usually available for rent. A half-day rental will do for most residential lawns.

Core aeration is usually a good idea for residential lawns, which are often compacted. It will create lovely air voids for the grass root zones. These void spaces also hold moisture to help grass through dry spells.

Core aeration is often followed by top-dressing the lawn with compost. This entails using a wheelbarrow and rake to put about an inch of bulk compost on the aerated lawn. This increases the organic matter on the soil surface, as well as down in the holes from the core aerator.

Many lawns will be ready for seed at this point. Be aware you may have to core aerate every spring and fall for several years to start seeing a difference. It’s not a short-term fix, but it is relatively easy and cost-effective.

Step 3: Till organic matter into the lawn soil

What if the dirt is still too hard to grow grass? Sometimes core aeration and a top dressing of compost just aren’t quite enough to create the well-draining soil grass loves. This is especially true when trying to plant grass in clay soil. The grass may grow, but it will never thrive. Weeds, bald spots, and puddles will always be an issue.

If the future lawn area is open and accessible, it’s possible to loosen and improve the dirt that’s already there (even if it’s clay). This is generally done by digging up the top few inches of the soil and mixing in organic matter. A common method is to use a rototiller machine and till in compost.

Tilling organic matter into the soil can be a bit drastic, especially if you use a machine….but it does work. In our area, tilling in leaves or composted manure is common. It’s a lot of work, but the organic matter holds air in the soil well.

Unfortunately, tilling can also bring up weed seeds. You’ll also have to spend extra time leveling out the soil before planting grass seed. Some people will till in the fall and level the soil a few times before and after winter to let the lumps and bumps out settle out of the lawn.

Step 4: Lawn soil overhaul – Bring in good topsoil

If all else fails (or is simply too much bother), consider bringing in high-quality lawn topsoil. Purchased topsoil can be placed on top of the existing soil. Since you know what you’re working with, you’ll have confidence that it’s well-draining, rich in organic matter, and has lots of lovely air voids in the root zone.

Bringing in good topsoil is what finally worked for us. It actually ended up being slightly less costly and time-consuming than we had assumed. We brought in a truckload of some really high-quality topsoil and just buried all the clay. No more tracking clay into the house, and no more trouble growing grass. It wasn’t cheap, but we don’t regret it one bit. Totally worth it!

By “good topsoil”, I mean real soil that has been dug out of the ground somewhere. Topsoil is mined as a whole product rather than mixed up from separate ingredients. It also shouldn’t be from anywhere that could have had toxic agricultural chemicals sprayed. There is also “manufactured topsoil” which can just be composted manure mixed with a bit of sand, sawdust, and wood chips.

In our area, we have a wonderful local supplier of OMRI-listed soil which is sustainably sourced and managed. If there is something similar in your area that could be a great option.

Buying good soil to cover up hard dirt

Topsoil in our area is about $40 a yard. Our pickup truck bed can hold about a yard, so you can think of the dirt price as $40 per pickup truck full of soil. We started with one pickup truck and it went so well, we decided to do the whole yard.

We ordered a total of 20 yards of topsoil for both the backyard and front yard. The topsoil came in 2 dump truckloads. Including delivery and taxes, the bulk order was about $900. It was enough to bury the clay in 6-8″ of topsoil. We watered and levelled the lawn area a few times to let the air pockets settle out, and then it was smooth sailing to turf town.

If you’re thinking of doing something similar, consider measuring your yard before you order. Also, be sure that you can change the grade of your property like that. You may only need to do a small area. Only do what you need to do! And be sure to source your mined topsoil from a sustainable producer.

Will grass grow through topsoil?

Most types of grass can grow through 2-3 inches of topsoil placed on top of it if the existing established plants are healthy. Grass often grows through topsoil when a thinner layer of topsoil is placed on top of an old lawn. Some of the grass (and likely the weeds) do survive the topsoil blanket and manage to push up through the dirt.

For this reason, it’s best to get rid of the weeds on an old lawn if the plan is to bring in a few inches of new topsoil. If the lawn is being renovated, and you’re here reading an article about growing grass on hard dirt, then there are likely a few weeds to deal with. Pull them out before placing the topsoil.

Does grass grow in fill dirt?

Grass will grow in fill dirt, but it won’t have the same access to nutrients as it would if it were growing in topsoil. Wild grass can even be seen growing on piles of fill dirt at construction sites. While turf grass will grow in fill dirt, it generally won’t thrive.

Fill is a construction material and should be free of organics, as it’s mined from the ground under the topsoil. Fill is great to “fill” up low spots in the ground, but doesn’t have the decomposed matter that makes topsoil so great for grass.

Grass to be planted on fill will do better if organic matter is worked into the soil before the seed is planted. Loose, un-compacted fill may be ok with just a few inches of homemade compost or topsoil placed on top of it. Compacted fill should be loosened up with a tiller or at least a core aerator prior to topping it with compost or topsoil. Grass grows much better in loose soil than compacted soil (even if the compacted soil is relatively well-drained).

Can you just sprinkle grass seed on the lawn?

Simply sprinkling grass seed on the lawn is a common method of seeding. Some of these seeds will probably grow, but many will not. This is how grass grows in nature; not all seeds turn into grass plants.

When you’ve paid for a bag of high-quality grass seed, it’s in your interest to give each seed the best chance to become a healthy plant. Purchased seeds have been carefully bred, grown, harvested, cleaned, packaged, and shipped to you. It’s worth taking the time to prepare the soil for it properly.

Even if you don’t have a lot of time to spare, do try to make sure most of the grass seeds are in contact with the soil. Grass seeds don’t have the best chance if they are caught up in other grass plants, in weeds, in thatch, or pretty much anything but nicely cultivated soil. At least rake them in a bit!

Take some tips from the pros

If you’d like to get super technical about bringing in lawn dirt, check out the USGA golf course green construction manual. They are serious about their grass growing…right down to constructing their grass soil beds with gravel drainage blankets and using a specified soil particle size distribution. If you’d like pro tips on building up the soil for your lawn, their construction manual is an excellent resource.

Planting grass seed in the improved soil

Once you’ve got lovely loosened-up soil, it’s business as usual in terms of grass seed planting. First off, get a high-quality grass seed. Grass seed is not the place to cheap out. Hedge your bets, and get a nice mix from a local store with knowledgeable staff. In our area, mixes of perennial ryegrass, fescue, and Kentucky bluegrass do well.

We once tried some bulk seed from a landscaping store that was SUPER cheap…..it turned out to be mostly “annual ryegrass”…..annual meaning that it only lasted one year. What a waste of time and money! Don’t cheap out on your grass seed after putting in so much work to your soil.

Once you’ve got good grass seed, make sure it’s well in contact with the soil. Follow the instructions on the bag, which usually include raking it in or sprinkling soil on top of the seed. The soil needs to be touching each grass seed for the best results.

Keeping grass seed well-watered during lawn germination

The final step? Keeping it moist during germination. Moisture is key to growing grass seed in any kind of soil. Keep the seeds moist. Don’t let the seeded dirt area dry out, but a mucky wet mess is no good either. It’s worth the time and attention it takes…soon the seed will establish itself and then it won’t be quite so needy.

Because consistent moisture is so key to growing grass seed, the best times of year to plant grass are in late spring (once the ground has warmed up), or in early fall (after the intense heat of summer has faded). You’re also less likely to be hit by a surprise watering restriction. Yay for early September lawn planting!