Maintaining a good lawn
By: Sandy Feather
©2009
Penn State
Cooperative Extension
Q.
Are there cultural practices that would
help keep my lawn looking good without constant maintenance?
A.
Deep,
infrequent watering during hot, dry weather is important to maintain
a healthy lawn. Deep watering encourages the turf to develop a
deeper, more extensive root system. Conversely, frequent, shallow
watering encourages a shallow root system. A shallow root system
means a lawn that is under drought stress when the top inch of soil
dries out. Use a sprinkler or an irrigation system to apply one inch
of water weekly to your lawn when rain is minimal. This is best
applied in one long, deep soaking session, rather than watering your
lawn a little bit every day. Our clay soils can only absorb about
one-half an inch of water an hour, so it should take two hours of
watering to apply an inch of water. To determine how long you have
to run your sprinkler or irrigation system, take a flat-bottomed
container such as a coffee can and mark off half-inch increments.
Place the can or cans where it will be hit by the water, and time
how long it takes to gather one-half inch of water. Then run your
sprinkler twice as long. You may need to apply water even slower to
steep slopes to avoid wasting water to runoff. It is best to water
in the morning. If you water during the heat of the day, too much
water is lost to evaporation. If you water at night, the grass stays
wet too long, and may be more likely to have disease problems.
Allowing your lawn to go dormant during hot, dry weather is always
an option. An otherwise healthy lawn can go about six weeks without
rain; it will turn brown, but should recover when cooler
temperatures and rain return.
A soil test
will help you design a fertilization program that provides what
your lawn needs for optimum health and growth. Inadequate or
excessive fertilization can limit turf growth. It will also tell you
what you have to do to get your soil pH (acidity or alkalinity) into
the optimum range of 6.5 to 7.0 that most lawn grasses prefer. Soil
test kits are available from your local Penn State Cooperative
Extension office for a nominal fee.
Typically, late spring (mid- to late May), late summer (late August
to mid-September) and late fall (mid-November) are the best times to
apply fertilizer. Liming is best done in fall. Limestone moves
through the soil very slowly and takes time to effect the desired
change in pH. If your soil test reveals that your lawn needs 100
pounds or more of limestone per thousand square feet, break it into
two applications, fall and spring.
You should also check your lawn for thatch. Older lawns often suffer
from a deep thatch layer. Thatch is nothing more than a layer of
organic matter between the soil surface and the crowns of the grass
plants. Dig up a small square of turf so you can look at the soil
profile. The thatch layer is easily visible. Thatch is created when
growing turfgrass sloughs off dead stems and roots. A thin layer of
thatch - one-half inch or less - is desirable. It acts as a mulch,
moderating soil temperature and maintaining soil moisture. More than
that creates problems, though. A thick layer of thatch can keep
water from reaching the soil, so your lawn is constantly
drought-stressed. And that creates more thatch. Thatch can also be a
breeding ground for insect and disease problems. Even worse, if your
lawn does develop a problem with white grubs (soil dwelling-insects
that feed on turf roots), a thick thatch layer can make it very
difficult to get an insecticide down to where the grubs are feeding.
The causes of
thatch include:
• The variety
of grasses in your lawn. Bluegrass and creeping red fescue are the
worst thatch formers of the cool season lawn grasses.
• A soil pH
lower than 6.5 immobilizes the microbes that break down thatch.
•
Over-fertilizing your lawn.
• Frequent,
shallow watering.
• Allowing
grass to grow too tall, and then cutting it and not collecting the
clippings.
A moderate
layer of thatch - between one-half and one inch - can be removed by
dethatching your lawn with a power dethatcher. Dethatching is very
stressful and should only be done in fall. You can rent dethatchers,
or hire a lawn service to do it for you. Run the dethatcher in one
direction, and then go over you your lawn in the perpendicular
direction. A good dethatching job should make you want to cry when
you look at your lawn. Topdress the lawn with a thin layer
(one-eighth to one-quarter inch) of good compost, then overseed with
varieties of turfgrass that match your existing lawn to help it
recover.
If you have over one inch of thatch, consider a total renovation -
removing your existing lawn and starting over. The knives of most
dethatchers will not go deep enough to get through the thatch and
down to the soil, which is important for a good dethatching job. A
good dethatching job is a lot of hard work, but will not be very
effective if you have over an inch of thatch.
If you do not have a thatch problem, but the soil is compacted, rent
a core aerator. Again, they are available from many tool rental
shops, or you can hire a lawn service to do the aerating for you.
Core aerators pull three to four inch plugs of soil out of the
ground and leave small holes behind. This helps aerate the soil
(yes, roots need air!) and alleviate soil compaction. Fall is ideal
for core aeration, but it can be done in the spring as well. If your
lawn does not have a lot of activity on it, core aeration every
three years or so will keep the soil aerated sufficiently. If all
the neighborhood kids play in your yard, consider yearly core
aeration in late fall to reduce soil compaction as much as possible.
You can break up the cores with a rake or allow them to stay on the
lawn where they will break up during winter’s freeze-thaw cycles. If
they are creating too much of a muddy mess (when children and/or
pets play on the lawn), you can rake them up and put them on the
compost pile.
Topdressing
with compost after core aeration is a good tool to slowly improve
the quality of the soil under your lawn without tearing it up and
starting over. A lawn is only as good as the underlying soil. A six
to eight-inch base of topsoil that contains a moderate amount of
organic matter is ideal, but few lawns have that luxury.
Thatching or
Dethatching
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