Answer: It won't be easy, but renovating your lawn will result in a lush, thick expanse of grass. Weeds can be removed manually or killed using an herbicide. It is especially important to kill perennial weeds before seeding. If weeds are primarily broad-leaved, the area can be treated with a broad-leaf herbicide. It is then best to wait 2-4 weeks before seeding. If large patches of grassy weeds such as quackgrass are present, a nonselective herbicide such as glyphosate (Roundup, Kleen-up, or others) can be used. This will kill most green vegetation it contacts, so be careful to apply only to those areas and plants you want killed. Be sure to follow label directions on how long to wait before seeding.
Avoid using weed killers that persist in the soil, such as soil sterilants. Select herbicides approved for use on lawns, and then follow the label directions explicitly. Once weeds have been destroyed and have begun to dry (usually about 5 to 14 days following application of a nonselective herbicide), renovation can proceed.
While early fall is the best time of year to renovate your lawn; grass seeds will germinate quickly in the cool temperatures of fall. Prior to seeding, a thorough soaking (to a depth of 6-8 inches) to replenish soil moisture will make soil preparation easier. It will also help ensure that young grass seedlings have sufficient water.
If needed, thatch can be removed manually with a garden rake (a very laborious process!), with a vertical mower (sometimes referred to as a power rake), or with a sod cutter. Where thatch is excessive, removal with a sod cutter is recommended.
A vertical mower can be used over the entire lawn whether or not there is some grass remaining, and can also be used for preparing the seedbed. The tines should be set to nick the soil surface to a depth of approximately 1/8 -? inch. Following vertical mowing, rake large clumps of debris from the site.
Alternatives to vertical mowing for soil preparation include vigorous hand raking (usually only practical on small sites) or extensive aerifying. Aerifiers (machines that poke holes in the ground and remove a small core of soil) are available at rental agencies. If you choose this method of soil preparation, aerify the lawn completely, going over it 3-5 times. Aerifier cores can be allowed to partially dry and then be broken up using a rake or vertical mower before seeding.
While more expensive, aerification followed by vertical mowing is recommended to prepare the seedbed. The important principle in seedbed preparation is to achieve good seed-soil contact. This will improve water supply to seeds and emerging seedlings during germination and establishment.
Just prior to seeding, about ? pound of nitrogen per 1000 square feet in a complete fertilizer should be applied. It may be lightly raked into the surface where the soil is bare and loose. This is approximately one-half the recommended label rate for most lawn fertilizers. Fertilization will encourage establishment and growth. If extra phosphorus and potassium are needed (as determined by a soil test), they are best applied following aerification and should be watered in prior to final seedbed preparation.
Best wishes with your new lawn!
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