Managing Thatch in Home Lawns
Thatch in lawns is often
misunderstood; both its cause and control. Some lawns have serious
thatch problems while others do not. Thatch
is a layer of living and dead organic matter that occurs between
the green matter and the soil surface. Excessive thatch (over
1/2 inch thick) creates a favorable environment for pests and disease,
an unfavorable growing environment for grass roots, and can interfere
with some lawn care practices. The primary component of thatch
is turfgrass stems and roots, and accumulates as these plant
buildup faster than they breakdown. Thatch problems are due to
a combination of biological, cultural, and environmental factors.
Cultural practices can have a big impact on thatch. For example,
heavy nitrogen fertilizer applications or overwatering frequently
contribute to thatch by causing lawns to grow excessively fast.
Avoid overfertilizing and overwatering. Despite popular belief,
short clippings dropped on the lawn after mowing are not the
cause of thatch buildup. Clippings are very high in water content
breakdown rapidly when returned to lawns after mowing, assuming
lawns are mowed on a regular basis (not removing more than
one-third of the leaf blade).
In our area, environmental factors
typically are another primary cause of thatch. Conditions favoring
thatch include heavy,
wet soils; alkaline, or high pH soils; and soil compaction.
common in northeast Illinois.
As thatch levels accumulate
to greater than 1/2 inch, lawn problems may begin and thatch
needs to be controlled. Thatch
torn out with a dethatcher or vertical mower, but will
return unless the cause is corrected. Mechanical dethatching
is also very
destructive to the lawn because roots are in thatch instead
of soil, so plants tear out easily. Overseeding is usually
afterwards. For this reason, it's best to tear out thatch
in late August for optimum reseeding timing.
followed by topdressing are two methods which will generally
correct the reasons thatch is accumulating.
aerifying machines will pull up small soil cores to the
surface, which are left there to act like topdressing. The holes
help solve problems such as compaction or poor drainage.
Topdressing is simply adding a thin layer(1/8 to 1/4 inch)
soil over the thatch, which adds microorganisms to help
Aerifying equipment may be rented or services are
available to do it for hire. Aerifying is an excellent lawn practice
many benefits, as it helps solve soil problems which
in turn leads to
better root systems and healthier lawns. Aerify in spring
or fall, making sure adequate moisture exists in the
over the lawn, the second perpendicular to the first.
An average of 15 to 20 aeration holes per square foot is suggested.
August/September 2004: Pet
Waste and Water Quality | Diseases and
Insects of Shrubs and Small Trees
| Fall Garden Wrap-Up | Managing
Thatch in Home Lawns