Ventilation is recommended for lawns with compacted soil, heavy thatch (more than 1 inch), or lawns with lots of bare areas. If a lawn is in poor condition, core aeration is recommended twice a year in spring and fall. It can be done annually to improve a compacted soil area, or it can be done every five years. Spring ventilation should be done when the soil is damp and the soil temperatures are above 50 degrees. The recommended time frame is May 1st to June 15th. Unfortunately, this is when most weed seeds germinate, which may be one of the reasons why your colleague said spring ventilation is “useless”. When core aeration is combined with fertilization and overseeding, a poor lawn can be helped immensely. And while autumn is by far the best time to do this, it can be done in spring to begin the process of rejuvenating a lawn.

Core aerators, also known as “hollow tine aerators”, can be rented. However, if you do decide to do so, make sure you get an aerator that will remove a good sized core and be sure to do the ventilation thoroughly without walking over tree roots and underground irrigation systems or invisible dog fences. Instead of doing it yourself, consider hiring one of the many excellent professional lawn maintainers in our area who can do this for you in no time for a reasonable fee.

For more information on lawn care, including new fertilizer recommendations, please visit our Wisconsin Horticulture website at http://hort.uwex.edu.