Overseeding Cool-Season Lawns
Some times hot weather, weeds, insects, or diseases can make our lawns look less than desirable. In these instances, it may be necessary to rejuvenate the lawn by overseeding. Overseeding is the practice of sowing seed into existing turf to fill in bare spots. September is the best time to overseed bluegrass, fescue, and ryegrass lawns.
The first step in lawn renovation is to determine and correct the conditions that caused the decline in the turf. If this is not done, the problem will likely reoccur next year.
Next, prepare the seed bed for planting. Mow the existing grass at 1 inch. This will help keep grass and weeds from competing with new seedlings. Likewise, the short mowing helps prevent seeds from lodging in tall grass and never reaching the ground. Work the soil lighting by using either a verticutter or powerake set to cut about 1/4 of an inch into the ground. Run the equipment in two directions and remove the thatch that it produces. Equally as good, a core aerator pulls plugs of soil from the turf and gives the seed a place to germinate and establish. Core aerators are especially useful for clay soil or compacted ground. It is best to make three to five passes over the area before seeding.
The seed must be kept moist for germination. Daily watering will be required until the seeds start to sprout. Slowly decrease your watering after three weeks.
New seedlings should grow as much as possible before winter. Apply a seed starter fertilizer at the time of seeding. Make another application of a complete lawn fertilizer eight weeks after seeding.
Mow the seedlings as soon as they reach 3 inches tall with the mower set at 2 inches. Continue to mow at that height for the remainder of the season.
When overseeding an existing turf grass, do not apply crabgrass preventers or broadleaf weed killers (like 2,4-D) six weeks prior to seeding or until after the seedlings have been mowed three times.
Over seeding is a simple and cost effective way to re-establish a sick or weak lawn. Proper seed bed preparation and maintenance will ensure a healthy stand of grass before the first frost. Remember to keep the newly planted seeds moist, and water once or twice during dry winters when the soil is not frozen.