Thatch is the layer of plant material build-up between the green top growth and roots. Thatch develops naturally as the grass grows. Some thatch is needed to protect the roots, but too much thatch prevents oxygen, moisture and nutrients from reaching the roots. Thick thatch prevents newly sown seeds from reaching the soil, and they sprout in the thatch layer. Thatch doesn’t insulate like soil does, causing the roots to dry out and the lawn to die. More water is needed for a heavily thatched lawn.
If your thatch measures more than 1/2″ between the top zone and root layer, you need to dethatch your lawn. Dethatching is necessary every 2–3 years, and is best done in the early spring before the active growing season begins.
The removed thatch can be composted and recycled back into the garden.