Q. I'm looking at a magazine ad for the Zoysia grass you sometimes talk about, and the claims look too good to be true. There must be some downside. Will it really replace my existing lawn if I plant one plug every foot like they say?
- ---Stephen in Spinnerstown, PA
- ---Phyllis in Chester Springs, PA
- ---Julianna in Oklahoma (zone 7, I think)
- ---Kris in Plymouth MA
What the ads don't tell you—they are advertising, after all —is that zoysia grass lawns go dormant in cool climes in the Fall, turning a tannish beige until they green up again the following Spring. Our Philadelphia lawn (USDA Growing Zone 6) was green about five months of the year. In warmer climes like Oklahoma, the green stage will be lengthier, with very little, if any, dormant time in the deeper South.
That's because zoysia is a warm-season grass, like Bermuda and St. Augustine. But while most warm-season grasses can't handle a winter chill, zoysia can survive cold weather, even in extreme areas like Massachusetts—and Michigan, where callers to our show have described decades-old zoysia lawns. BUT those lawns are only green for three or four months of the year. Northerners who don't want a light brown yard should stick with the classic cool-season turfs: Kentucky bluegrass, the fescues, perennial rye, or blends of those grasses.
Now, we always warn that cool-season grass seed must be sown in the Fall for the lawn to thrive; that's probably why Kris in Massachusetts wonders if she missed the planting window for this year. She would have missed it for a cool-season turf, but warm-season grasses are installed in the Spring, not the Fall. And very few warm-season grasses grow well from seed, so you generally plant sod, sprigs or plugs. (Zoysia plugs are just punched out of rolls of sod, so they're kind of the same thing.)
Till up the soil as soon as its dry in Spring, rake away as much of the old green material as you can, level the surface, apply an inch of compost, well-aged mushroom soil and/or high-quality, dark-colored topsoil, level that, plant your zoysia plugs and keep them watered until they start spreading sideways. Warm-season lawns get a closer cut than cool-season ones, so leveling the surface first is essential if you want to avoid bare spots. (Its actually essential no matter what kind of grass you grow; an un-level lawn will never look as good as it should.)
That inch of compost and/or topsoil on top is also essential, as it will prevent lots of the buried weed seeds you uncovered from sprouting and provide a nice base of organic matter for your new lawn. If you can afford it, buy more than the recommended number and plant the plugs closer than directed; the faster it fills in, the fewer weeds you'll have to worry about. (This is true of all warm-season grasses, not just zoysia.)
After it's established, cut zoysia at about two inches high and feed it LIGHTLY while it's actively green and growing; two feedings from the Philadelphia area North, one in late Spring and one in Summer. You can feed three times in warmer regions where the turf is green longer, but don't go nuts; zoysia is just not a heavy feeder.
Use an organic fertilizer that provides about a pound of Nitrogen per thousand square feet of turf each time. Ten pounds of corn gluten meal per thousand square feet would be ideal, providing exactly the right amount of food, and—thanks to its natural pre-emergent herbicide capability—preventing any of those dormant weed seeds from sprouting. At least it will if the corn gluten is labeled as a natural pre-emergent herbicide and licensed by Iowa State University (as all of Gardens Alive's CGM products are). Corn gluten sold as animal feed is an inferior fertilizer, and won't provide any weed protection.
IMPORTANT NOTE: All warm-season grasses are fed in the warm months. Centipede grass is a light feeder like zoysia, but the others all want a little more Nitrogen each time—say 15 to 20 pounds of corn gluten per thousand square feet, or other natural lawn fertilizer that provides a pound and a half to two pounds of Nitrogen each time. But don't feed bluegrass, fescue or rye in the summer; cool-season lawns are on a very different feeding schedule. See this Previous Question of the Week for more info on the care and feeding of cool-season grasses.
Back to zoysia: Once established, it is such an aggressive grower that deep edging is absolutely necessary to keep it from creeping into adjoining flowerbeds or such. (Install this barrier when you put the plugs in; it's really hard to establish a Maginot Line AFTER the fact.)
Our zoysia lawn also needed a good de-thatching every summer with a specialized rake. This produced little haystacks of dead material I used to think would make sensational mulch, until Iowa State University Turf Grass Professor Dr. Nick Christians warned me that the seemingly dead rhizomes could still spring back to life—just where I didn't want them.
Oh, and while our listener is correct that zoysia is generally considered a full-sun turf, Dr. Christians rates it as actually having pretty good shade tolerance. You wouldn't want to plant a full shade area with it, but it should do okay in in-between spots.