Aeration, Over-Seeding, and Fertilization
You can't teach an old lawn new tricks. Eventually competing with weeds and dealing with other lawn stresses will cause an old lawn to have trouble maintaining vigorous growth.
Aeration allows oxygen to get to the grass roots and the soil to allow it to breathe. After aeration takes place, water is able to permeate into the soil and get direct access to the root system of the grass. The soil in your lawn gets compacted throughout the year, which restricts oxygen and and actually promotes weed growth such as crabgrass. Aeration loosens the compacted soil and breaks up the thatch allowing the root system to grow more easily. By helping roots grow before winter sets in, you are insuring that the lawn will green-up quicker in the spring and become more resistant to disease and drought.
Over-seeding is an important practice that should be implemented in your lawn maintenance program at least every 3 to 4 years (even if your lawn is already thick). However, if the results you are looking for is a lush, green lawn that fends off weeds, insects and diseases, a combination of core aeration and over-seeding should be done annually. Also, every year new varieties of grass species that may be resistant to drought, disease, or insect damage enters the market, so it is beneficial to integrate the new grass into a lawn with older varieties without these features.
Now that we have prepped your lawn for new spring growth, we need to maximize the results and fertilize just before your lawn goes dormant. Fertilization replenishes the nutrient supply that was used up throughout the summer months, as well as adds additional nutrients to the turf in order to sustain it over the cold winter months. Fertilized lawns have increased shoot density, improved fall, winter, and spring root growth, and enhanced storage of energy reserves within. A complete lawn fertilization program is an essential part of every great looking lawn.