Types of Aerators

• Core aerators use a hollow spoon or "tine," which penetrates the ground and pulls a "plug" of soil out of the ground. The next plug ejects the previous plug from the tine, depositing it on the lawn. Spike aerators press a solid spike into the ground. This does not remove anything and the resultant opening is created by compacting the soil to the sides of the spikes.
  
  

Effects

• In core aeration, cleanly incised holes allow water, nutrients and air to move into the root zone in abundance. The cores deposited on the lawn move soil micro-organisms onto the top of the thatch, where they can work from the top down, instead of always working from the bottom up. While the cores are unsightly for a few days, they quickly break down and improve the lawn.
  
  Spike aeration does nothing to redistribute soil micro-organisms and the much smaller holes do not allow as much penetration of water, nutrients and air as core aeration. In addition, the sides of the holes are compressed, rather than cut, restricting soil absorption.
  
  

Potential

• While spike aeration is better than no aeration, it does not match core aeration in effectiveness for lawn renovation or maintenance. Spike aerators cost less than core aerators, but for most homeowners, renting an aerator is a much more economical approach than buying. Most rental yards have core aerators available at hourly, half-day or full-day rates. The Virginia Cooperative Extension Service suggests neighbors pitch in together to split the rental fee and the work.
  
  

Timing

• Either type of aeration should be done when the grass is actively growing. For cool-season grasses (bluegrass, fescue, and perennial rye) that means mid-spring and mid-fall are optimum times. For warm-season grasses (zoysia, St. Augustine, Bermuda and centipeide), early summer and late summer are best.
  
  

Considerations

• Preparation for aeration does not differ between the two methods. The lawn needs to be moist but not muddy. If you have a rental reservation, and Mother Nature has not cooperated with some rain a day or two in advance, you should water the lawn. Know and mark the location of irrigation heads, cable television lines and telephone lines. Water lines and electric lines should be far below the reach of an aerator in most climates, but knowing their location and avoiding the area with the aerator can avoid an expensive and/or dangerous surprise.