If your lawn has been looking sad recently, it's time to give it some first aid. Even if you don't keep a perfectly manicured lawn, you probably know that thick, healthy grass serves as the perfect backdrop for colorful gardens, trees and other landscape features. And, it's nice to walk on.
More important, as lawns thin out, weeds begin to take over. Of course, you can attack weeds repeatedly, but it would be smarter to encourage your grass to grow thicker.
Autumn is the best time to plant grass seed, but the window of opportunity for reseeding is quite short. In the Twin Cities and southern Minnesota, the best time to reseed is from mid-August through mid-September. If you live farther north, you'll need to finish seeding sooner.
When you reseed, it's not necessary to match the type of grass already in your lawn. If you over-seed the entire lawn, not just thin areas, the results shouldn't look patchy.
If you want a luxuriant lawn and your yard is sunny for a good part of the day, there are many "improved" Kentucky bluegrasses and bluegrass-perennial rye blends from which to choose. While they are attractive, Kentucky bluegrasses and blends demand more frequent fertilizing, watering, mowing and dethatching than common Kentucky bluegrass and fescue blends. (Chances are, these are the kinds of grasses you already have if your lawn was sodded rather than started from seed.)
If you'd like a lower-maintenance lawn, plant common Kentucky bluegrass -- varieties such as "Park,"Newport,"Nugget,"Parade,"Kenblue" or "Touchdown"-- in areas that are predominately sunny. In shadier areas, use fine-leaved fescues such as creeping red fescue, chewings fescue and hard fescue. Fine fescues are typically labeled specifically for shady lawns. However, not even these seeds can rescue a lawn that has become densely shaded as your trees have matured.
Buffalo grass, a native grass touted for its drought tolerance, isn't a good choice for most lawns because, like zoysia grass, it's a warm-season grass. That means it's slow to come out of dormancy and turn green in spring, and that it turns brown with the first frost.
Preparation and care
Before you seed, run a dethatching machine (also called a "vertical mower") or core aerator across the lawn in two or more directions. Set the dethatching machine so it bites through thatch and slices into the soil. This creates the channels that allow seeds to reach open soil, where they can germinate and grow. If possible, water the lawn thoroughly a day or two before you dethatch so the soil isn't hard and dry.
If you're only seeding a small area, you can dethatch with a heavy metal garden rake and muscle power, but it's hard work. Rake up the debris that's raised by dethatching, but leave the plugs of soil left behind by an aerator. Within a few weeks they'll crumble and "top dress" the lawn.
Spread both seed and starter fertilizer, then water lightly. Continue to water frequently and lightly twice daily unless the soil surface remains moist. Because seedling roots are shallow, concentrate on keeping the uppermost part of the soil moist. As seedlings grow, you can begin to water less often, but for longer periods of time.
Mow the lawn once it's about 3Â½ inches tall, but only take about one third off the top. Even if the new grass seedlings look a bit wimpy this fall, you'll be pleasantly surprised to see a thicker, more attractive lawn next spring.
Deb Brown is a horticulturist with the University of Minnesota Extension Service Yard and Garden Line. For help with garden, plant and insect questions, call the Yard and Garden Line at 612-624-4771.