Aeration is a Natural Weed Control Process: Courtesy: Nutri-Lawn, your Ecology Friendly Lawn Care company (informational advertisement) The Professional Lawn Care Association agrees that after proper mowing, aeration is the most important thing that you can do to promote healthy grass growth. It is a natural means to help control weeds. What is Aeration? It is the mechanical means to open and loosen soils- alleviating compaction, and also reducing thatch, for better grass growth, without destroying the beauty of the grass in the process. What is Compaction? It is the settling and packing together of the soil materials. It is caused by foot traffic, lawn mowers, vibration from traffic, weather including rain and snow. With compacted soils, roots cannot grow and expand, and water and nutrients cannot get to the roots. How does it Reduce Thatch? By opening up the soil, airflow is improved which stimulates microbial action. Microbes feed on thatch and convert thatch back to topsoil. How does it help to control Weeds? Weeds grow best in compacted hard soils. Grass grows best in soil that is loose where roots can spread easily. With time aeration will promote grass growth and thickening. Thick grass will crowd weeds out, and eliminate bare soil areas where weed seeds have the opportunity to germinate. When and How Often should you Aerate? The need for aeration is dependent on soil type, grass type, and compaction conditions (e.g. amount of traffic). Clay soils compact hardest. Kentucky Blue Grass is most likely to have heavier thatch build-up. Proper aeration requires that you loosen the soil and keep it loose all year long. For a typical residential lawn, the ideal situation is to have two aerations per year - once in the spring and again in the fall. The spring aeration alleviates compaction from the winter,s snow build-up and traffic, and opens the soil for nutrients to get to the plant for growth and greening. The fall aeration is done again to reduce compaction which occurred over the summer and stimulate root growth when roots are most active. If you choose to do one aeration per season only, either time is highly beneficial.