From the Sperry Garden – May, 2012

When Even St. Augustine Starts to Thin

Great landscapes begin with turfgrass, and shade trees are almost always the next plants to go in. Sooner or later, those two will break out into war. As the trees get larger, the shade gets denser. That’s when the grass starts to fade away, and that’s about the time that people sit down at their computers or pick up their phones, saying, "I’m going to ask Neil."

Unfortunately, a big number of those people who come seeking my help never follow my advice. They just keep planting more grass, until one day they finally realize that all grasses need a certain amount of direct sunlight – and that their space just doesn’t measure up. If the lighting falls short, the grass starts to thin, and bare ground is left in the wake.

That’s how it is in the Sperry home landscape. We’ve lived in our house for 35 years, and during that time, our trees have doubled in size. That’s true of the big native pecans that tower over almost all of our landscape, and it’s also true of the Mexican plum that stood off to my left as I took this photo late yesterday afternoon.

When trees get that much larger, that means that grass won’t be getting enough light to hold its own, and that’s what you’re seeing in the lower left corner of my photo. I’ve watched as probably 90 percent of my turf has died away over the past 25 years, and I’ve gradually changed out every bit of it to shade-tolerant groundcovers like mondograss, purple wintercreeper euonymus, liriope, ferns and Asian jasmine.

I’ve learned over those years that the dividing point between adequate light and insufficient sunlight is about 4 hours of direct sunlight per day. At 4 hours or more, I can solid-sod St. Augustine (our most shade-tolerant turfgrass) and expect it to hold its own. However, if I expect my St. Augustine to grow and spread, I’m going to need at least 6 or 7 hours per day. You can add two hours to each of those numbers if you’re trying to grow bermudagrass.

The little bald area around the stepping stones is going to continue to enlarge unless I take some type of corrective action. I can either prune yet another branch off the Mexican plum, so that more light can sneak in beneath its canopy, or I can change this part of the garden into plantings for sun and other plantings for shade. Since I’ve already done just about all the pruning I want to do on the tree, I’ll probably opt for the latter, and this fall may be my time to make those changes.

My points in all of this are first that landscapes are constantly evolving. They’re works-in-progress, and you just keep tweaking and fixing. And, I’ve also learned to think things through, that is, to be patient with my decisions. I’ve been watching this situation evolve over the past several years, and I’m getting closer and closer to a major change out.

The one thing I won’t do is to plant more grass here. There’s simply no point in adding to my  frustration.

If you have thinning turfgrass, before you do anything, look at your trees’ shadow patterns. If there’s a direct correlation between the heaviest shade and thinnest turf, then you’ve found your way into my world. Best bet is that you, too, will soon be making some changes.

Posted by Neil Sperry
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