Aerating Your Lawn
by Nancy Bolton
Core aeration is a recommended cultural practice to maintain and encourage a healthy lawn. It is especially important for compacted, heavily-used turf and those with thatch buildup of more than half an inch. Aeration is a process that removes small soil plugs or “cores” from your lawn. Each core is 1/2 to 3/4 inches wide and 3-6 inches long. Depending on the machine, the holes are about 2-6 inches apart. These finger-like cores are deposited on the lawn itself and will disintegrate and filter back down into the soil after it rains. Mingling soil and thatch hastens the decomposition of thatch.
What will aeration do for my lawn?
Aeration helps improve root zone conditions by relieving soil compaction while controlling thatch. Compaction occurs in clay-based soils and in those that are heavily used by play or parking. Compaction is most severe in poorly-drained or wet sites after the site dries. This compaction reduces the space in the soil that would normally hold air. Grass roots need oxygen to grow and absorb nutrients and water. The result of this lack of air in the root zone is poor top growth and lawn deterioration.
The Virginia Cooperative Extension experts believe that core aeration benefits your lawn by:
- Increasing the activity of soil microorganisms that decompose thatch
- Increasing water, nutrient and oxygen movement into the soil and allowing carbon dioxide to get out
- Improving rooting
- Enhancing infiltration of rainfall or irrigation (better drainage)
- Helping prevent fertilizer and pesticide run off from overly-compacted areas
How do I know if I need to aerate?
As mentioned, lawns with compacted soil leading to thin turf need aeration. In addition, those lawns that have more than 1/2 inch of thatch also could benefit from aeration. If in doubt, remove a square foot section of lawn at least 6 inches deep. If grass roots extend only into the first 1-2 inches, your soil is compacted. With cool season grasses such as fescue, the roots will be at their shortest at the end of the summer.
When do I aerate?
In Virginia, the best time to aerate for cool season lawns is in the cooler weather of the fall. Spring is an alternative though. Root extension is the longest in the spring, but aerating in the fall aids in the production of new roots. Fall is the time of the year for vigorous growth and lawns will quickly recover from the aeration process. Weed competition is the least at this time as well. Do not aerate frozen ground nor newly seeded or sodded lawns in the first year. Also, do not aerate during drought conditions.
How do I aerate?
- Mow the lawn low — this is something you will never hear me say otherwise!
- If it’s dry, water thoroughly — meaning about 1″ of water. Do this about 2 days prior to aeration. It may take more than one watering if it is not being absorbed and there is runoff. The soil should be moist — but not wet or the cores will stick in the hollow tines of the machine.
- Rent an aerator at a local rental center or hire a landscape company. Be sure the machine has hollow tines that are 4 inches deep.
- Run the aerator in at least two different directions to insure good coverage.
You can watch a video that shows how to aerate a lawn. Find the video at “Aerating Your Lawn” Video (this video features Tom Thompson, head of the Department of Crop and Soil Environmental Sciences at Virginia Tech and Head Golf Coach Jay Hardwick and was filmed on the Pete Dye River Course, a top-ranked college golf course on the campus of Virginia Tech).
Other things to know:
- Aeration helps to control thatch.
- It is difficult to core-aerate heavy soils that have stones, rocks or tree roots.
- Mark sprinkler heads or underground cables and lines that could be damaged by the aerator.
- Soil cores are best left on the lawn. It may take 2-4 weeks for them to disintegrate.
- Lawns may be fertilized and seeded immediately after aeration — with or without soil top dressing.
- If your soil is heavily compacted, apply mature compost about 1/4 inch deep before seeding.
- In general, aerate once a year. One time is not a quick fix.
To reduce compaction during the winter….
- Keep the lawn clear of lawn furniture, toys or debris
- Remove leaves from the lawn
- Avoid excessive lawn foot traffic
- Avoid parking a truck or car on any part of the lawn
- Avoid walking on lawn if there is frost or ice
- Ensure that appropriate “ice melt” chemicals are selected to minimize possible environmental effects. Avoid using those with nitrogen and phosphorus.
“Aerating Your Lawn,” Virginia Cooperative Extension Publication, pubs.ext.vt.edu/430/430-002
“A Lawn to Dye For — How to Create a Perfect Lawn: Aerating Your Lawn” Video Series, Virginia Cooperative Extension, pubs.ext.vt.edu/CSES/CSES-38
“Bsic Turf Management Principles — Core Cultivation or Aerating,” Colorado State Cooperative Extension Publication, CMG GardenNotes #551