Horticultural experts generally agree that proper lawn care in the fall has a greater impact than similar efforts in the spring or any other season for developing a great lawn throughout the year.  Fall is the season when turfgrass growth begins to slow. It is also a good time to help your grass develop the stamina it will need to survive the stress of winter and get a head start for the coming spring.

September is generally the right time to focus additional attention for cool-season (northern U.S.) grasses, while the latter part of the month is best for warm-season varieties found in the more southern locations.

Cool Season Lawns (Kentucky Bluegrass, Fescues and Ryegrass) 

To achieve maximum benefit for year-round results, fall lawn care requires a number of different efforts, including mowing, removal or mulching lawn debris, aerating, fertilizing and watering. The sequence of these efforts is as important as how they are performed.

Mowing
In addition to the immediate beauty of a freshly cut lawn, mowing in accordance with the following guidelines can help generate and maintain healthier turfgrass plants.

• Make sure the mower blade is sharp-the ragged cut made by a dull blade tends to shred the grass blade tips, exposing a larger surface area to disease, pest and water loss.
• Set the proper cutting height-the higher cutting height used during the summer (when the photosynthetic processes in the leaf tissues are at their peak) should have progressed to a lower cutting height late in the fall when the plant begins to store food reserves. The lower cutting height, without scalping, helps harden and strengthen the plants' roots and crown with increased nutrients that would otherwise have been used by longer grass blades.
• Lawn Debris-up to one inch of leaves can be mulched to serve as a protective cover during the coming cold season. However, clumps or large leaves, as often accumulate in low spots, could trap dampness and become a breeding spot for diseases and pests. If in doubt, remove the debris with a mulching mower and dump it the compost bin for recycling into a nutrient-rich amendment for future garden use.

Aerating the Soil
After a year of a being trampled upon by various activities that tend to pack the soil, the grass roots need a breath of fresh air (oxygen) for respiration that only proper aeration can provide. This helps the root systems better establish themselves for the coming winter. Aeration should take place approximately two weeks before applying the year's final fertilizer, or five to six weeks before the first frost.

The most effective aerator has hollow tines that penetrate the ground and remove plugs of soil that are expelled as each successive hole is made, leaving a vent for true aeration. Although a freshly aerated lawn appears a bit unsightly with numerous plugs laying all over it, they will eventually dissolve, returning nutrients to the soil for use by the grass.

The unsightly appearance can be reduced and the plug dissolving process speeded up by mowing with a low-cutting blade once the plugs are dry. Be sure to remove the grass clipping bag and then mow the entire lawn in a left-to-right pattern, followed by an up-and-down pattern to assure even break-up and spreading of the aeration plugs. After mowing, watering the lawn further helps dissolve the aeration plugs.

Fertilizing/Weed Control
The fall application of a weed-and-feed type fertilizer provides longer lasting benefits to a lawn than that of any other time of the year. Fertilizer should be timed about one month before the first frost. It is very important to read, understand and follow instructions on the fertilizer label. The following information should take the mystery out of how much and which type to fertilizer to buy, and how to apply it efficiently.

• How much-The fertilizer bag label advises how many square feet the product will cover, any portion not used will be just as effective next year, if stored in a cool, dry area.
• Which type-Any reputable lawn and garden retailer will be able to recommend the best fertilizer mixture for a particular time of the year. Many companies sell a 'Winterizer' product that will produce the greatest benefit to your lawn.
• Proper application-For proper coverage a broadcast spreader should be used. This reduces the likelihood of misapplication. To assure uniform coverage with either a broadcast spreader or a drop spreader, follow these simple steps:
  1. Adjust the spreader application dial to one-half of the fertilizer bag's recommended setting and make the first application in an up-and-down pattern, covering the entire lawn.
  2. Begin the second application immediately, in a left-to-right pattern, and continue over the entire lawn.

Reseeding
Fall is the perfect time to seed cool season grasses.  In the colder climates you will want this done by September 15th in the warmer areas October 15th.  Seed any bare spots after raking the area.  Make sure the seeded areas stay moist until the grass has grown in.  If you choose to reseed make sure you check the label on your herbicide, many herbicides will inhibit the growth of young plants. 

Warm Season Grasses (Bermuda grass, Zoysia grass, St. Augustine, Centipede grass)

In the areas where frost hits and these grasses go dormant it is important to make sure that the grass is treated well before it turns brown.  In the warmer climates the fall is a time to do no harm.  Often after a long hot summer homeowners try and do to much to their lawns and love them to death. 

Fertilizer/Weed Control
Most Warm season lawns can use a fertilizer application in September.  Applying nitrogen at a rate of 1 pound per thousand square feet can increase the plants rooting.  Use a product that has both slow release and quick release forms of nitrogen.  A later fall application of potassium can also help with winter survival.  A preemergent weed control application is usually suggested in the fall so that cool weather weeds do not overtake the lawn as it rests for the winter. 

Aerating
Fall aeration of warm season lawns is not suggested.  It can lead to increased disease pressure.

Overseeding
This is the process of seeding a coolseason grass into a warm season species so that the area can have a year round green appearance.  This should be limited to golf courses, sports fields and high traffic areas.  The overseeded grass protects the dormant species from extensive damage and helps reduce erosion that could be caused by the wear of a dormant grass. 

The best place to find detailed instructions for lawn care in your particular area is through a local agricultural extension service.