The scourge of lawn gardeners everywhere, thatch is a buildup of dead material within a carpet of grass. This natural occurrence can build up over time until it begins to cause damage and dullness to a lawn. More common to some types of lawn grass than others, thatch can be fought using good lawn care practices and some simple but effective maintenance.
Thatch is a thick layer of dead grass and organic material including living and dead organisms that can build up below the surface of lawn grass. Usually occurring in some amount in every lawn, thatch buildups become more of a problem when they become more than 1/2 inch thick.
When thatch strikes, it can weaken a lawn in many ways. The density of thatch can choke out roots by limiting their growth and the oxygen they receive. Thatch buildup also provides an inviting harbor for diseases and insect pests that can cause severe damage to a lawn, particularly the lawn-sucking chinch bug, a small black winged insect with saliva that slowly kills grass.
Treating Lawn Thatch
Getting rid of thatch buildup requires either lawn aeration or vertical mowing. In lawn aeration, a machine pokes holes in a lawn to give the roots room to breathe. The process creates unattractive holes in a lawn which heal up quickly, but may not work for more severe thatch buildup. Vertical mowing is more efficient than aerating in treating severe thatch problems.
A buildup of thatch can occur in any lawn under the right conditions, but it is particularly common in St. Augustine lawns. Prevent thatch buildup in a lawn by avoiding over-fertilizing with nitrogen and mowing the lawn regularly, removing no more than one-third of the height of the grass blade at a time.
The best time to remove thatch is in the late summer. Because thatch buildup can cause the roots of the grass to take hold in the thatch instead of the soil, thatch removal can often tear up a significant amount of grass. Some dethatched lawns will sustain enough damage that they need to be reseeded.