I grew up in College Station about the time that the Houston Astrodome was opening. Almost immediately, they discovered that grass wasn’t going to grow in the shade of the outfield, where they’d put some kind of sunscreen to help the outfielders see the fly balls.
An agronomist down the street from us took on the task of finding a shade-tolerant grass that could also handle low mowing and pedestrian traffic, but unfortunately, we all know how that turned out.
To this day, AstroTurf or one of its modern counterparts is still the only option for turflike coverings in really shady parts of our landscapes. Let me put that in even simpler terms: There is no lawn grass that will survive with less than five or six hours of hot, direct summer sunlight daily. None. Not a one, in spite of all those preposterous claims you’ll see and hear every spring.
The grass and company names change, but the promises are the same. “Grows in total shade.” “Almost never needs water.” “Mow it monthly.” “The newest thing in easy lawn care.” And, for the most part, they’re all just bags of hot air.
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Trust your instincts, gardeners. These “miracle” grasses are a come-on, and they simply won’t do what they say they will do. You’ll notice that their claims are most often in the form of amateur testimonials, seldom in the form of bona fide university research reports.
So let’s move on. What can you do when you have heavy shade and the grass starts to thin? First, you confirm that it is indeed the shade that’s causing the problem. Watch the shadow patterns over a couple of sunny days. If it’s the areas nearest the trunk (where there is the least sunlight) that are balding out first, you don’t have enough light.
St. Augustine is our most shade-tolerant turf grass. Although it grows best in full sunlight, it will hold its own down to as few as five or six hours of direct summer sun. When it gets shadier than that, you’ll begin to see more soil and less grass. It will happen over a couple of years if you had St. Augustine there from the outset.
However, if you’ve planted St. Augustine sod to replace Bermuda that has already thinned and died out, the new St. Augustine sod may not do much better. Not only is it coping with a lot of shade, but it’s also having to deal with the shock of having been dug with only 1/2-inch of topsoil and transported many miles to its new home.
That can set the grass back enough that it doesn’t recover.
Critical note from Neil: Somewhere about here is where thousands of gardeners are in total denial . “It can’t be the shade. The grass just a few feet away is doing just fine. It has to be competition for water or nutrients, or maybe there’s a disease in the soil or rocks in the root zone.” I may have heard every possible excuse, and I’ve learned to listen quietly, smile gently, and say simply, “I’m sure you’ll figure it out.” Those folks, I have found, need more time to realize that it’s lack of light, pure and simple, that is causing their problems.
Once you’ve caught up with reality and are willing to acknowledge that shade does cause grass to thin and die, you might consider removing one or two lower branches, to allow more early morning and late evening sun to reach the grass beneath the tree. However, do so only if you’re sure it’s going to be enough light to make a big difference.
Even more critically, prune only if you won’t be disfiguring the tree’s natural form.
Let’s say, however, that you’ve already tried the St. Augustine. You swung and you missed. Then you removed lower branches, and the next pitch came in “Strike Two!” Still no grass.
The good news is that your next chance will be a success if you just take a breath and allow yourself to switch over to a shade-tolerant ground cover. These are vines and low, clumping plants that give a lovely floor to your shaded forest, allowing you to bypass further angst brought on by the shade.
You can have an entirely different and gorgeous garden without having to plant grass there ever again. There are many fine choices.
For the lowest ground cover plants, my standard go-to plant is regular mondograss. It’s not a true grass, but it has the fine blades and grasslike texture. You can walk on it occasionally if you must, but it’s not made to be mowed, and it’s not going to tolerate ongoing traffic. It covers quickly, and it holds soil firmly. Plant 4-inch pots checkerboard-style on 12- to 15-inch centers, and it will be almost solid by winter. Dwarf mondograss would seem even better, but it’s far too slow-growing, and it’s a bit more sensitive to drought and even soil-borne diseases. I use it in smaller spaces.
I’ve used a lot of liriope in our shaded areas. It’s the big sister to mondograss, and it also produces handsome lavender or white floral spikes in the summer. And I’ve included trailing full-sun ground covers like Asian jasmine and purple wintercreeper euonymus as well.
Wood ferns and aspidistras are taller possibilities. And, as many ground covers as we have, there are even more shrubs, small trees, annuals and perennials that will thrive in the shade. All of these are good stewards of Texas water. They won’t use more than their modest allotments.