Lawn thatch is the layer of dead turf grass tissue between the green vegetation and the soil surface that must be removed (a process known as dethatching) to maintain lawn health. Lawn thatch is derived from stems, leaves, stolons, rhizomes and roots.
A layer of organic matter that begins to grow between the base of a plant and the soil. Usually discussed as a problem with lawns as dead roots and stems accumulate. Proponents of the organic philosophy say that in an organic program where soil has achieved a healthy balance, microorganisms are present to feed on mulched grass clippings and prevent thatch. However, if long grass (generally meaning growth of more than a week) is cut and mulched, there may be an excess of clippings which is too great for the existing population of microbes to handle in a timely way. Use your own judgement in determining how much is too much, then remove excess clippings from the yard and put them into the compost bin. Clippings of any length that are wet or matted should be removed from the lawn and placed in the compost bin.