lawn care company is recommending dethatching for my lawn. I am
curious as to how important that is to maintaining a healthy lawn.
A.Thatch is a by-product of the normal growth of turfgrass. It
is a tangled mat of organic matter between the crowns of the grass
plants and the soil surface, formed as the grass sloughs off dead
roots, rhizomes and/or
stolons and stems. How quickly it forms and breaks down is governed
by the type of grass in your lawn, the pH of the soil and your
mowing, watering and fertilization practices.
1/2-inch or less of thatch is actually desirable.
It acts as a mulch to conserve soil moisture and moderate soil
temperature. The organic matter stimulates microbial action, which
makes nutrients more
available to the turf. Thatch becomes a problem when it gets more than about
a half-inch thick. Once it dries out, it actually repels water, much
like dried-out peat moss. It also serves as a breeding ground for
insects and disease. Worst of all, if you run into a problem with
white grubs, it makes it difficult to get an insecticide down to the
turf roots where the grubs are feeding. Instead, the active
ingredient of the pesticide binds to the thatch layer, rendering it
faster approach to thick thatch removal...
Kentucky bluegrass and creeping red fescue are the
fastest thatch formers typically grown in home lawns. This is
because they spread by rhizomes, or underground stems. Perennial
ryegrass, turf-type tall fescues and hard fescues are bunch-type
grasses. They do not spread by rhizomes, so they build up thatch
A soil pH under 6.3 inactivates the microbes
responsible for breaking down the thatch layer. It is important to
test your soil every few years to make sure the pH remains in the
optimum range of 6.5 to 7.0.
Proper mowing is another important way to slow the
thatch-formation process. Ideally, you should never remove more than
one-third of the blade of grass when you mow. This means that you
have to adjust your mowing frequency to how fast the grass is
Also, there is a proportional relationship between
the height of the grass and depth of its root system. The longer the
grass, the more extensive root system it will have. In spring and
through summer, raise the cutting height to 3 inches to encourage an
extensive root system. You should cut it a little shorter in fall,
with the final cutting before winter down to 1½ inches. If you
cut your grass short during the heat of summer, it will become
stressed and the dead grass and roots will contribute to thatch
A sure way to create a thatch nightmare for yourself
is to overfertilize your lawn. While nitrogen makes a lawn green, it
also makes it grow. If you push your lawn with excessive nitrogen,
it grows faster and forms thatch faster.
For a typical bluegrass/ryegrass/fescue lawn, 2-3
pounds of nitrogen per thousand square feet over the growing season
is sufficient. That should be applied in two to four applications.
More than that is asking for trouble. Not only does excessive
nitrogen encourage thatch formation, it also makes your lawn more
susceptible to certain insect and disease problems, especially
during hot, humid weather.
Finally, make sure to water deeply and infrequently.
Shallow, frequent watering encourages a shallow root system that is
easily drought stressed. When those drought-stressed roots die, they
simply add to the thatch layer.
On the other hand, deep watering encourages a deeper,
more drought-resistant root system. Deep watering means letting the
sprinkler or irrigation system run for two hours or so once or twice
a week. This should apply about an inch of water that will wet the
soil to a depth of 6-8 inches.
If your lawn has less than a half-inch of thatch,
core aeration every couple of years, along with proper mowing,
watering and fertilization practices, should be sufficient to keep
the thatch layer at the proper level.
If you have more than a half-inch but less than 1½
inches of thatch, running a power dethatcher in fall should remove
enough thatch to save your lawn. Run the dethatcher in one
direction, then again in the perpendicular direction.
Smaller lawns can be done with a hand dethatching rake.
Large or small, a nice lawn adds curb appeal
A good dethatching job may make you want to cry when
you look at your lawn -- since it will be torn up pretty
thoroughly. That is why dethatching is best done in the fall, so
your lawn has ample time to recover before facing the next summer's
heat and drought.
Rake away the debris and topdress with a thin layer
(1/8 to 1/4 inch) of good quality topsoil or compost. Then overseed
your lawn to help it recover.
If you have more than 1½ inches of thatch, consider
starting a new lawn from scratch. The tines on most power dethatchers are not long enough to get through that much thatch and
into the soil. Once the new lawn is established, follow good
cultural practices to avoid thatch buildup over coming years.