Q. We desperately need to re-grade our yard due to pooling and hazards to children – tripping and such. I know you've said that Spring isn't the best time to sow grass seed in our region, and so we have made room in our budget to use sod. I realize we will need to water it carefully and consistently. Is there any more specific advice you can give? Are there different kinds of sod? Thanks very much,
---Kay in Bala Cynwyd, PA
A. Thank you, Kay! Sod is one of those subjects that somehow hadn't made it into a Question of the Week yet, and this is a great time of year to discuss the basics!
Now, you are correct that the best time to sow cool-season grasses like fescue or bluegrass is mid-August through the end of September; the soil temp is perfect for fast germination, and the progressively cooling weather allows the young grass to outcompete crabgrass and other now-weakening summer weeds.
But that's just for cool-season grasses. If you live in an area where a warm season grass is the better choice, spring is the best time for installation (and 'heavy lifting' work like core aeration). Warm clime growers just need to wait until the soil is warm enough to germinate the seed or accept sprigs, plugs or sod. But there's no downside to waiting a bit, as the warm-season grasses—Bermuda, zoysia, St. Augustine and centipede—get stronger as the weather gets hotter.
Back to cool-season climes; sod can be installed with great hope of success in the spring (or the fall, but seed makes more sense then). Because the grass is already germinated, the cold soils of Spring aren't an issue, and cool-season grasses love growing in the mild temperatures of Spring. Just be sure to get the site prepared and the sod down as early in the season as possible, so that your new lawn is well-established before summer heat arrives. (It would be very challenging to try and install cool-season sod in the heat of summer, when cool season grasses are at their weakest.)
The big downside is that North or South, Sod is much more expensive than seed. But if you can afford it, it provides an instant lawn that if well managed, should never see a weed.
In the mid-Atlantic region, you'll generally find two kinds of sod for sale: Kentucky bluegrass and turf-type tall fescue. Bluegrass thrives in the sun, and because it's a creeping grass, can fill in its own bare spots. Fescue is more tolerant of shade, but fescues are clumping grasses that can't fill in their own bare spots. (So if you do install a fescue sod, it is essential that you first make sure that matching seed will be available for future overseeding and repairs.)
Now, Iowa State University Turfgrass Professor (and weed-and-feeding corn gluten meal pioneer!) Nick Christians has some important tips to offer concerning the installation of sod. The first is about freshness. Nick stresses that you want to have the soil surface completely prepared before the rolls of sod are delivered. Sod that's packed for transport can't sit around in hot sunny weather for more than a day before it starts to brown. You'll have more wiggle room if the weather is cool and cloudy, but if it's going to sit for any length of time, Nick still suggests rolling the sod out temporarily in a shady spot.
I would personally want to inspect the shipment before it arrives. And be picky; if either bluegrass or fescue can work in your situation, choose by the condition of the sod.
Our listener is already going to have the area regraded, which is great. But she mentions water pooling up, and that scares me. She—and others in such situations—might want to go the extra mile and install drain tiles during the grading process. All lawns require good drainage.
Speaking of soil preparation, Nick adds that you need to think about the height of your bare dirt. When you seed a lawn, you typically add good soil (or preferably, compost). But when you sod, you need to remove some soil because the turf already has a considerable height of its own. "The finished grade before sod is laid," says Nick, "should be about an inch lower than for a seeded lawn—or about one and half inches below nearby hard surfaces."
Now, sod is heavy to begin with, and bigger rolls are enormously heavy—but they're also going to provide the best coverage with the fewest possible gaps, so consider having a professional do the job. They'll have the equipment, muscle and manpower—and experience—to get it done right.
If it's a small job that you'll attempt yourself, rough up the soil surface so the roots can get down there easily; and make sure that surface is level. (Whether you start with seed, sod, sprigs or plugs, a level surface is essential to achieving a good looking lawn.) Lay the sod in a staggered pattern ("like brickwork", explains Nick) and don't try to stretch any pieces out to make it all fit. Press the pieces tight against each other, or you'll create gaps.
After it's down, 'roll' the sod lightly to insure good soil contact with the roots and then water it deeply—to a depth of four to six inches. Don't overwater after that, and 'keep off the grass' until new growth begins—which should take about 10 to 14 days.
And for those folks who just want to improve or replant a cool-season lawn that's already in place (but doesn't please them), the smart money says to just feed what you have with corn gluten meal or a bagged organic lawn fertilizer this Spring, cut it at three inches high and begin planning for a reseeding project later this summer. Nick feels strongly that cool-season grasses installed in late August are virtually bulletproof!
Oh, and Gardens Alive seems to have developed a cool-season grass that's the best of two worlds: Its said to have the slow growth and shade tolerance of a fescue and the capacity to spread and somewhat self-repair. Very interesting! If you give this grass--that they call Turf Alive III with Rhizomes--a try this fall, let me know how it works out for you!