FOR SEA Institute of Marine Science K-12 marine science curriculum and teacher training

Lawn Maintenance

  Lawn
Maintenance

Most of
us have a lawn of some description already established. Proper
maintenance practices must be followed to keep the lawn healthy.

Mowing


The
correct mowing height is probably the single most important
factor in the formation of healthy turf. Correct height is important
because of two opposite growth patterns in grass. On one hand,
the taller the grass, the deeper the roots penetrate, tapping
into a larger volume of moisture and nutrients. On the other
hand, as the height of grass increases, the density of shoots
decreases, which can contribute to weed infestation if the mowing
height is then lowered. Cut your grass frequently enough so
that no more than 1/3 of the grass blade is removed at one mowing.
Weekly mowing increases shoot density. Mowing should always
be done with a sharp blade. Grass clippings do not require removal
unless they present an aesthetic problem. They usually break
down quickly, do not contribute to thatch buildup, and actually
add nitrogen to the soil.

Cultivation


Lawns
require cultivation by aeration and thatching. Aeration removes
small cylindrical cores of soil from the lawn, allowing water
and air to penetrate. Home lawns usually require aeration
only once every two to four years.

Thatching
removes the mat of old grass rhizomes at the surface. The
mat prevents the penetration of water and fertilizer. Thatching
may be done with a thatching rake or machine when the layer
exceeds about 1/2 inch.

Fertilization


Apply
fertilizer at the proper time and in the appropriate quantities.
Look for fertilizers with a 3- 1-2 ratio of nitrogen, phosphate,
and potash such as the commonly available ’15-5-10.” Avoid
combination fertilizers/weed killers whose application amounts
to indiscriminate broadcasting of herbicides whether or not
a problem exists.

Soil
tests, generally recommended every two or three years, are
useful in determining the necessity of fertilization. Excessive
fertilization is a waste of resources and can damage plants.
Always follow label directions and consult WSU Cooperative
Extension publications for general recommendations. Timing
is very important. If you only fertilize once in the Puget
Sound area, do it in mid-November. Since timing of this application
coincides with the start of the rainy season, it is especially
important not to over-fertilize as the excess fertilizer may
be carried away in stormwater runoff where it can decrease
lake clarity and promote excessive algal growth, robbing the
water of oxygen. If you fertilize twice, do it in late June
and again in November. Such timing encourages strong root
systems which can support vigorous top growth through the
spring and summer.

Watering

Over
watering causes runoff, wasted water and sets the stage for
lawn problems. Infrequent, long irrigation cycles allow moisture
to penetrate, encouraging deep roots and drought resistant
plants. Frequent, short cycles encourage shallow roots which
are easily stressed.

Our lawns
absorb water at a rate of 3/10 inch per hour. Unfortunately,
most irrigation systems deliver up to 1 1/2 inches per hour.
What the lawn cannot absorb pools in low areas or becomes
runoff that can carry pollutants into stormdrains, creeks,
rivers, lakes and Puget Sound.

Lawn
Watering Guide

Average
Depth

in Test Cans
 1/8″ 1/4″ 3/8″ 1/2″ 5/8″ 3/4″ 1″ 1
1/8″
Minutes
to Water Every

Third Day in Spring		 30 15 10 7
1/2 		6 5 4 3
1/3
Minutes
to Water Every

Third Day in Summer		 60 30 20 15 12 10 8 6
2/3
Minutes
to Water Every

Third Day in Fall		 24 12 8 6
 4
3/4 		4
 3
1/3 		2
1/2

Use
this chart as a guide. Decrease watering times and frequencies
during cool or humid weather. Skip at least one scheduled
watering after any substantial rainfall.

*This
chart was prepared by the Washington State Nursery and
Landscape Association and WSU Cooperative Extension.

Your
lawn needs about 1 1/2 inches of water per week. To find out
how much water your irrigation system produces, place several
flat-bottomed tuna fish or cat food cans around your sprinkler.
Turn on your sprinklers for 15 minutes. Measure the amount
of water in each can and add the amounts together. Divide
this total by the number of cans to find the average amount
of water sprinkled in 15 minutes. Refer to the chart on the
right and read the number of minutes you should water, every
third day.

Finally,
water in the morning before 10 a.m. for maximum uptake. Evening
watering is an acceptable second choice, while mid-day watering
wastes water and can stress plants. Adjust your sprinklers
to avoid watering the sidewalk, driveway, or street. Low cost
water timers to shut off flow are readily available in garden
and hardware stores and will prevent over-watering if you
forget to turn off your sprinklers.

The last
component in your lawn care maintenance program, pest management,
is treated in the previous chapter.