Q: My lawn is in very sad shape. I think sod might be the answer, but I’m afraid that tilling the soil to prepare the ground will seriously damage the roots of my trees and shrubs. Is there a safe way to sod this area? — Cere Goodman, Shell Knob, Mo.
A: Sod is not your answer. It may have the look and feel of a cure-all for sorry lawns, but there are only a handful of situations that call for it. For one thing, your grass is struggling in shade, and much of the sod produced for the northern two-thirds of the country is either pure or predominantly bluegrass, which needs full sun. So sod won’t do well in the shade under your trees. It’s also much more expensive, roughly five times the cost of a seeded lawn, and you must be prepared to water it frequently or the investment may be lost. Even on sunny sites, sod is advisable only when the lawn is on a steep slope or has to be planted immediately, regardless of the season. A good seed mix, on the other hand, will contain a blend of several varieties, some of which will perform better in certain parts of your yard than others. This blend increases the odds that the spot under your oaks will look as good as the sunny swath down the middle.
Seed makes better lawns, but seeding works well only in late summer and early fall or (less so) in very early spring. Most Northern grasses prefer cool weather and go dormant in summer. An early heat wave can damage young seedlings planted in spring, whereas a lawn seeded in the fall will have many more months to establish itself before the hottest summer days. As you suspect, sod does indeed require that the ground be tilled up, and that won’t be good for your tree roots. Also, preparing the ground properly for sod is exactly the same as preparing the ground for seeding a brand-new lawn. Instead, you should renovate the lawn around your trees, using a core aerator or slit seeder. Then plant named varieties of grasses that are more shade-tolerant: red fescue or chewings fescue. You can safely use a slit seeder or core aerator around your trees and shrubs as long as you avoid places where the roots are exposed. Forget about trying to force grass to grow there; plant shade-loving perennials or ground covers instead.