Problems growing grass on clay soil with heavy shade

Asked September 17, 2018, 7:26 PM EDT

Hello, I’m a homeowner that has been trying to grow grass on the west side of my house for the past 30 years. The soil is very heavy clay and to compound the problems it also sits under 150 year old white oak trees. This spring I tried the following: used a Scotts shade seed, with black dirt that I rake over the clay soil to get some grass but not much. I also tried 2 pieces of sod where I removed the clay soil and planted the sod. I know that most sod is made for sunny areas so I was not surprised that sod basically died. I have a irrigation system that I use because the crown of my old oak trees does not allow rain to penetrate the ground under them. Is there a grass seed that I can use that will give me better results. Please review the photos bellow. any help would be greatly appreciated Tom Scanlon 763.545.0669/home 763.226.4046/cell

Hennepin County Minnesota

3 Responses

Greetings! Thank you for contacting AaE for help.

Clay soil is a very minor issue when it comes to grass because that area has two things going against growing grass, shade and tree root competition.

It'll have to be either the tree or the grass but it's not likely you'll be able to have both. You could consider installing a ground cover that can tolerate dry shade such as Wild ginger (Asarum canadense), bergenia (Bergenia cordifolia), vinca (Vinca minor), cranesbill (Geranium spp.) or Lady's mantle (Alchemilla mollis). Check out the information on the U of MN Extension web page about gardening in the shade where you can find lists shrubs (evergreen and deciduous) that can tolerate shade. https://extension.umn.edu/planting-and-growing-guides/gardening-shade

Best of luck!

Thanks for the prompt reply. I will expand my Hosta garden but I still would like to plant some grass where there is grass growing. I had a tree expert advise me to add lime to the soil and sweeten it so grass would grow. Is this a good idea? What is the best shade tolerant grass available? Can I add top soil to cover the clay and get a grass to grow? Thanks in advance for your help,

Tom Scanlon

Hello,

Lime is only recommended when the pH of the soil is too acidic to grow grass. The ideal pH for growing grass is between 6.5 and 7.0 for Kentucky bluegrass and 6.0 and 6.5 for fine fescues which are recommended for shady areas. Most soils in your part of Minnesota fall within these ranges. A soil test will help you determine if you need to add lime. I would do that before adding lime because too high a pH can be harmful as well. I've included a link to the U of MN Extension soil test web page below where you can learn more about how to submit a sample.
The soil test will also advise on soil amendments for growing grass. Adding topsoil will encourage the tree to extend roots into the new layer and eventually compete with any grass that's growing there. But amending the soil around the tree can result in harming the roots of the tree that are already there. So it's a difficult decision to make.

If you decide to test your soil, be sure to dig several batches of soil 6 to 8 inches in around the area of concern, mix it up and then take the amount they recommend for the test to send in. You might also let them know about the tree in the area so that they can make the best recommendation for amendments if any.

I hinted earlier that fine fescues is the best type of grass to grow in shade. Here is more information about growing grass from the U of MN Extension that includes comparisons of different types of grasses: https://drive.google.com/file/d/1BR8tdbWA0sioluGgUmWPSZo1rqXbUktk/view

I hope this information helps.