Over-seeding Lawn in Autumn

Image of dead patchy grass

By Vijai Pandian, Horticulture Educator, Kenosha and Racine Counties

After stressful summer, lawn grasses in Wisconsin rejuvenate in autumn and it is considered one of the best times to seed, renovate and establish new lawns. Moderate temperatures in 70’s and ample soil moisture in September promotes speedy establishment of lawn grasses. Summer annual weeds like crabgrass ends its life cycle in September and doesn’t compete with the newly seeded grass.

The first step in lawn renovation is to identify the cause of lawn decline and assess the spread of damaged area. This year’s summer heat and drought stress caused multiple bare patches, and thin lawns in southeast Wisconsin. Compacted soil, chinch bugs, shade, lack of fertility and diseases (necrotic ring spot, summer patch) can also further stress the grasses in summer months. Lawns with more than 50% desirable grasses, can be renovated by over-seeding bare patches. However, lawns that has more than 50% weeds or bare ground requires a complete renovation.

Following are some useful tips in over-seeding an established lawn:

  1. Start by selecting right seed mix for the given site. For sunny areas, use 50-100% Kentucky bluegrass mix and for dry shaded sites use 50% or more with fine fescue mix.
  2. Take control of perennial weed patches like creeping Charlie, by using broadleaf weed control product containing triclopyr as active ingredient. Follow the label directions for safety and direction. Schedule a second application at about 10-14 days interval for effective control.
  3. Small bare patches are about the size of baseball may require some broadcasting with general lawn fertilizer (1lb of Nitrogen per 1000 square feet rate) to boost the surrounding turf grasses to fill in the voids.
  4. To fix dead patches about the size of basketball, loosen the soil, sprinkle the right type of seeds by hand and rake the seeds gently to a depth of 1/4to 3/8 inch.
  5. To over-seed larger areas or to improve turf density, rent a slit seeder from a local hardware store or garden centers. You can also seek service from professional lawn care companies to slit seed your lawn. Slit seeders make a small groove in the soil and deposit the seeds. The flap attached at the back end of the slit seeder covers the deposited seed with soil. Run the slit seeder at two perpendicular directions to each other using half the seeding rate to get a uniform dense lawn growth.
  6. It is important to irrigate, mow and fertilize the over-seeded area for successful establishment. Keep the over-seeded area moist until it is established. Use a clean straw to mulch it lightly (one bale per 1000 square feet). Begin mowing when the seedlings reach 3 inches tall (takes about 3-6 weeks) and fertilize six weeks after germination with general lawn fertilizer.

For more information on lawn care, check out our Lawn Care Section.

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