Mid-August through mid-September is the best time to renovate a thin lawn. Sowing grass seed in late summer has several advantages over spring seeding. Cool-season grass seeds germinate quickly in the warm soils of late summer. Once the grass germinates, the warm days and cool nights of fall promote rapid turf growth. Also, there will be less competition from weeds as fewer weed seeds germinate in late summer and fall.
If possible, determine and correct the problem causing the lawn to decline. Possible causes include poor care, insects, disease, drought, excessive thatch, and unsuitable turfgrass species.
Next select the best suited turfgrass species for the site. In sunny areas, Kentucky bluegrass is the best adapted turfgrass. Heavily shaded areas should be seeded with the fine- textured fescues. Creeping red fescue, hard fescue, and chewings fescue tolerate considerable shade and form a fine-textured turf. When purchasing grass seed, select high quality seed.
Before seeding, mow the lawn as short as possible. If renovating small areas, prepare the area by raking the thin spots. Sow the seed by hand. After seeding, work the seed into the soil by raking the area a second time.
Large areas can be prepared by using a core aerifier or power rake. If using a core aerifier, go over the lawn three or four times in different directions. Rake and remove all debris after power raking the lawn. After the site has been core aerified or power raked, sow the grass seed using a seeder. Then work the seed into the soil by lightly dragging or raking the area. Large areas can also be overseeded by using a slit seeder. A slit seeder makes small groves in the soil and deposits the seed directly into the slits. Core aerifiers, power rakes, and slit seeders can be rented at many garden centers and rental agencies. After seeding, keep the areas moist with frequent light applications of water. Once the grass begins to germinate, water less frequently but more deeply.--
This article originally appeared in the July 16, 1999 issue, p. 95.