Your grass needs to breathe, too. Gently raking your lawn, or “dethatching”, increases movement of air, water, and nutrients into the soil by removing debris. This debris is known as thatch. Thatch is particularly thick in the springtime. It’s made up of garden junk: old grass stems, roots, clippings, and leaves that have not fully decomposed. This stuff sits on the surface of your soil, out of sight below the grass line, choking your lawn. Thatch build-up is caused by poorly aerated soil, excess nitrogen, infrequent mowing, setting your lawn mower blade too high, and excessive mulching. For very serious cases, where thatch is more than 2.5 cm (1 inch) thick, consider using a verti-cutter, or motorized dethatcher, to save time.