Answer: If it were my lawn, I would spend the time and effort to completely renovate it. Your efforts now will be repaid for years to come as you enjoy your healthy new lawn.
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.
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. 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.
Following soil preparation, you are ready to seed. The primary objective is to distribute the seed uniformly over the area to be planted. This can be achieved on very small sites (less than 8 feet across) by hand. When using this method, it is a good idea to mix about 1 part seed with 4 parts of sawdust or a material like Milorganite to promote uniform seed distribution. For seeding larger areas, a rotary or drop spreader can be used, or the seed can be planted using a slit seeder. A slit seeder cuts shallow furrows in the existing turf and drops seed in these furrows. This requires some skill to operate properly and is generally best done by a professional. Regardless of the method you choose, the best way to achieve uniform distribution of seed is to divide the amount of seed required to cover the area in half or quarters, and apply seed in several different directions (such as north-south followed by east-west). In areas where no vegetation remains, rake lightly to help work the seed barely into the soil. If all seeds are buried, most of it will be planted too deep?leave about 10% of the seed showing on the surface. Where approximately 50% live grass remains in the lawn, overseeding with 1-2 pounds/1000 square feet of Kentucky bluegrass or 2-3 pounds/1000 square feet of a mixture of grasses should provide enough grass seedlings to fill in and cover the lawn surface.
Where no grass exists or where the soil has been tilled and is essentially bare, the rates for seeding should be about 2-3 pounds/1000 square feet for Kentucky bluegrass or 3-4 pounds/1000 square feet for a grass mixture. After seeding, water the soil lightly. Excessive watering can wash seeds away or wash soil over them, and can increase the risk of fungal attack. If soil moisture is sufficient, it may only be necessary to water the seedbed once or twice daily for a few minutes each time to prevent drying out. Note that seeds are not killed by moderate soil drying, but seedlings can be. Once seedlings have emerged, watering duration should gradually be increased. Watering frequency may be decreased as the lawn becomes established.
Mowing should first take place when grass blades are 3-4 inches tall. Mow them to a height of 2? inches with a sharp mower. As the lawn thickens the mowing height can be reduced gradually to the desired height. Traffic and play on a newly renovated lawn should be avoided for the first several weeks after seedlings emerge. Remember?a dense, healthy lawn reduces noise levels, cools the environment, filters dust and pollen out of the air, and is one of the safest playing surfaces available. A successful renovation will increase these benefits to you as well as contribute to aesthetically pleasing surroundings.
Good luck with your lawn renovation!
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