There seems to be a real problem determining what thatch is... Conversations about thatch have become impossible because one person is thinking grass clippings and another is thinking, living and dead roots and stems growing in a tangled mess above the surface of the soil... This dense layer is typically hydrophobic and keeps the ferts and water at or near the surface, thus perpetuating the problem with roots continuing to grow upwards where the N is... It is this kind of thatch that is man-made and it it this kind of thatch that aeration is designed to overcome the problems of... Question is : What do we call grass clippings and are they even a problem?