How to Grow Grass Under Trees
Advice from Roger Cook on growing grass in the shade
I’m having trouble growing grass because of four big oak trees that shade my lawn. Is there a type of grass seed that will withstand heavy shade?
—Rich Levy, Royal Oak, MI
Most lawn grasses prefer full sun—about 6 hours’ worth—and don’t do well in shade. But there are some shade-tolerant fescues that will handle your cool climate. Creeping red fescue (Festuca rubra) is one of the best for shade. It needs only a couple of hours of direct sunlight per day, and doesn’t mind if there’s more. It’s called “creeping” because it sends out horizontal underground stems called rhizomes that enable it to colonize bare patches.
If you want to give that fescue a try, early fall is a good time for planting because the weather is usually cooler and wetter. First, have your soil tested, and check with your cooperative extension service to see if fertilizer needs to be added. F. rubra prefers relatively infertile soils. Order enough compost to cover your lawn with a layer 1⁄4 inch thick, and rent a slice seeder; it’s the best way to plant grass seed over a wide area. Set it to dispense seed at half the rate recommended on the machine, then cover your lawn with slightly overlapping passes, first in one direction, then at 90 degrees to the first passes. Spread the fertilizer, if needed, then the compost, and water gently and frequently until the seeds germinate. You should see green shoots within two weeks and a lush lawn by next spring.
Once established, F. rubra in the shade does not like to be heavily watered. And it will do better if you leave it 3 to 4 inches long; longer blades capture more sun than short ones.
To help your new grass thrive, consider hiring an arborist to give your trees a judicious pruning. A thinner, higher canopy will allow more light and rain to reach your grass, and go a long way toward ensuring a lush green lawn. So will long, less-frequent waterings early in the day. Both the tree roots and grass roots should be reaching deep for water, and not competing with each other on the surface. A half-inch of water twice a week is a good rule of thumb for loamy soils. You’ll need less water if you have clay soil and more if your soil is sandy.
But if there are spots where even this fescue can’t survive, then try planting a shade-loving ground-cover such as pachysandra instead.