Cool-Season Grasses: Lawn Establishment and Renovation
Brad S. Fresenburg and John H. Dunn
Department of Horticulture
Establishment of turfgrass brings beauty to any landscape. While preparing
an area for turf, do not hurry the process. Mistakes made at that time will
be evident later and will cost extra in time and labor. The success of a beautiful
turf is dependent on many factors, including initial soil preparation.
General steps to turfgrass establishment
- Obtain a soil fertility test and fertilizer recommendations
- Rough grade
- Apply lime if needed
- Apply fertilizer as recommended by soil test
- Apply organic amendments if needed
- Till materials listed above into top 4-6 inches of soil
- Perform finish grading
- Apply starter fertilizer and work into top inch of soil
- Apply seed
- Rake or drag to cover seed lightly
- Roll lightly
- Mulch
- Water
- Mow
- Control weeds
Preparation of the site
You may not need to follow all of the above steps to establish your lawn. For
example, the soil need not be completely tilled where grading and soil amendments
are not required and when soils are not excessively compacted.
Once soil has been tilled, considerable time and effort are required to prepare
a firm, granular seedbed. Where surface grade and soil physical conditions are
acceptable, lawns can be re-established with minimal effort by killing the existing
undesirable vegetation and incorporating seed into the surface. (See lawn renovation
section.)
Regardless of how the site is prepared, it is important that seed be incorporated
into the top 1/4 inch of soil. On loose, bare soils, this can easily be done
by lightly raking the seed into the surface. On hard compact soils or soils
with existing vegetation and thatch, the seed should be mechanically incorporated
into the soil by verticutting, slit-seeding, or intense coring. Scattering seed
on the surface without incorporation is a waste of time and money.
Soil testing
A soil test is needed to determine the lime and fertilizer requirements
to ensure good turfgrass establishment and future growth. The test results provide
your soil pH value and if lime will be required. A soil pH between 6.0 and 6.8
is optimum for turfgrass growth. When pH is optimum, other nutrients such as
nitrogen, phosphorus and potassium are readily available from the soil for plant
uptake. Lime is used to raise soil pH, and sulphur is added to lower pH. Phosphorus
and potassium needs, if any, will also be indicated on the soil test report.
Phosphorus is especially important for root development and seedling establishment.
Phosphorus is most effective when incorporated into the top 4 to 6 inches of
the soil because it moves downward slowly.
Soil testing and sample bags may be obtained from your local MU Extension
center for a nominal fee. Send soil for analysis two months before your planting
date to allow sufficient time for you to receive fertilizer recommendations
and purchase the appropriate materials.
Soil preparation
Proper attention to grading for surface drainage and conserving or
developing topsoil will lead to easier care of your lawn in the years to come.
Push aside existing topsoil when construction or excessive grade changes are
required. Topsoil will be evenly spread over the site once the rough grading
is completed.
When building a new home where a basement or foundation is dug, insist that
the excavated subsoil is not combined with the existing topsoil. Trees, shrubs,
groundcovers and lawns never develop to their full potential in poor quality
subsoil. The initial investment in retaining on-site topsoil or amending poor
quality soils will avoid the agonizing replacement of plants that could not
tolerate the poor soil environment.
The area should be rough graded with gentle slopes to adequately drain or
divert surface water without erosion. Slopes with a 1-foot drop in 50 feet should
be adequate, but should not exceed a 1-foot drop in 15 feet. The finished grade
should slope away from the foundation. On sites where topsoil is added over
subsoil, be sure that the finished grade is at least 3 inches below the top
of the foundation of basement homes. Surface runoff can cause basement flooding
if water runs over the basement foundation. Remove all debris such as large
stones, tree roots and discarded construction materials that will interfere
with turfgrass root growth and water movement through the soil.
Liming and fertilizing
Apply the required amount of lime, phosphorus and potassium recommended
on the soil test report for establishing a lawn. Where a soil test is not available,
and if soils have required liming in the past but have not been limed for at
least two years, apply 25 pounds of finely ground limestone per 1,000 square
feet. Also apply 5 to 7 pounds of 0-46-0 phosphorus fertilizer per 1,000 square
feet. Phosphorus is not very mobile in the soil and should be incorporated in
the root zone (top 4 to 6 inches of soil) during this step. Nitrogen and potassium
are highly mobile in the soil and easily can be distributed by surface application.
Thoroughly till the lime and fertilizer materials into the surface 4 to 6
inches of soil. Do not exceed 3 pounds of 0-46-0 fertilizer per 1,000 square
feet if nutrients are not to be incorporated into the top 4 to 6 inches of soil.
These practices are aimed at building the basic soil fertility to an acceptable
level.
Broadcast and work into the top inch of soil 5 pounds
of 20-27-5 or 19-25-5 fertilizer or 10 pounds of a 10-24-18
fertilizer, or the equivalent, per 1,000 square feet. The fertilizer should be turf grade and contain 30 percent or more
of the total nitrogen as water-insoluble or controlled-release nitrogen. Application
at the recommended rate should provide adequate nutrition for the first three
months of growth.
As an alternative starter fertilizer, apply 10 pounds of 10-10-10 or 12-12-12
farm-grade (soluble nitrogen) fertilizer or equivalent per 1,000 square feet
(for example, 5 to 6 pounds of 20-20-20 fertilizer per 1,000 square feet). Using
nitrogen fertilizers that contain only soluble nitrogen will necessitate additional
nitrogen after six to eight weeks of growing weather.
Soil amendments
A soil test will indicate if organic matter is required. Organic matter,
such as peat moss or compost, can be added to clay soils to improve drainage
and aerification. The same organic matter can be added to sandy soils to help
hold water and nutrients in the soil. Fresh organic matter -- manure, straw
or fresh saw dust -- is not usually recommended because it can cause a temporary
nitrogen imbalance that will lead to slow growth and grass yellowing.
Reed-sedge peat and moss peat are also good sources of organic matter that
tend to last longer in the soil than most other organic matter sources. Organic
matter should be worked into the top 2 to 4 inches of soil before applying the
starter fertilizer.
Final grading
Rake the area to the finish grade just before seeding. Light rolling
will indicate any low spots or other irregularities to the area. A proper final
surface will be firm enough to prevent ruts made by seeding equipment but will
be loose and crumbly so that seed easily can be raked into the top 1/4 inch of
soil. Once these steps have been properly followed, you are ready to install
a turf by seeding or sodding.
Installation of turf
When to establish
Selecting the right time of the year to seed cool-season grasses is
the most important factor in successful lawn establishment. The best time to
seed cool-season grasses is between Aug. 25 and Oct. 1. Lawns seeded within
a week of Labor Day are more likely to fill in completely by winter and produce
a thicker appearance the following spring than lawns seeded in October.
Seeding in late summer is preferred because temperatures are still warm enough
to promote rapid germination when provided with rain or irrigation. The cooler
temperatures and shorter days of the approaching fall are ideal for further
growth and development of young seedling grasses.
Establishing cool-season grasses from seed in the spring can be extremely
difficult. In some cases, complete failure should be expected. Rainfall or watering
required to germinate turfgrass seeds during spring establishment will also
promote excessive weed growth, especially crabgrass. If you are lucky enough
to beat the crabgrass, expect to continue the battle with frequent summer irrigations
to prevent moisture stress. Even if moisture is adequate, summer temperatures
may severely thin or completely kill seedling turf. The constant summer watering
required by seedling turf will also increase the chance of Pythium damping off
and brown patch. Both of these fungal diseases are encouraged by the same conditions
that promote seedling growth -- wet soils, frequent watering and summer
nitrogen.
Sod of Kentucky bluegrass or tall fescue can be installed during most of
the year except in mid-winter when the ground is frozen. When extreme heat and
drought conditions exist in summer, sod should be cut and laid during a 12-
to 24-hour period. If done under drought conditions, the turf must be kept moist
and cool. The soil should be watered enough to cool it before installation.
It should be thoroughly watered again immediately after the sod is laid.
Seed vs. sod
A quality lawn containing the recommended mixtures of specific grass
varieties and species can be established with either seed or sod. When seeding,
however, there are many more species and varieties from which to select. Most
sod grown in Missouri is straight Kentucky bluegrass or a mixture of mostly tall
fescue combined with a small amount of Kentucky bluegrass. Some tall fescue sod
is also available on plastic netting.
Initially, seed is less expensive than sod. However, successful establishment
is more risky with seed than with sod, and if reseeding of certain areas or
even an entire lawn is necessary, the overall expense may be less with sod.
Also, the area is exposed to erosion because of the time required for seed to
germinate and become well rooted in the soil. Sodding practically eliminates
such problems, a consideration that may be especially important on steep hills
or banks. Sod also reduces the chance of pesticide and nutrient contamination
from surface runoff.
Sodding provides an immediately pleasing turf that is quickly functional,
and it will compete with viable weed seed already present in the soil. Seeding
usually requires weed control during the first year of establishment.
Seed should be used to establish lawns only in early fall or early spring,
whereas sod offers less time limitation in that it may be established in nearly
any season. Sodding of cool-season grasses in the spring is preferred to seeding.
Seeding
Before seeding, be sure that the soil has been prepared properly and
is smooth and level.
Seed small areas by hand. A fertilizer spreader can be used in larger areas.
When seeding by hand, try to apply five to 10 seeds per square inch. Heavier
seedings will cause weak, spindly seedlings and spotty establishment. Calibrate
spreaders to supply half the amount of seed in one pass over the area. Divide
the amount of seed to be sown into two groups. Spread the first group of seed.
Then spread the second group at a right angle to the first group.
Rake the seed to cover it with 1/8 to 1/4 inch of soil. Roll lightly to make
good contact between seed and soil. Use a light layer of straw as mulch -- one to one and one half
bales per 1,000 square feet. This helps hasten germination, keeps soil moist
and protects young seedlings. The soil should remain moist from the surface
to just below the active root zone.
At first, this moist zone will be shallow and require light, frequent irrigation.
Use a fine spray to sprinkle seeds one to four times per day until young seedlings
are established. As the grass develops, irrigate deeper and less frequently. Always avoid puddles and runoff.
Sodding
Sodding is the installation of commercially grown turf. Sod has a carpetlike
appearance consisting of green shoots attached to roots and soil. It usually
comes in 3-foot sections, 18 inches wide, with less than 1/2 inch of soil attached.
Sodding has the advantage of almost immediate establishment, but its disadvantages
are initial cost and the high amount of labor involved.
Choose high-quality sod that is actively growing. Sod is perishable and should
not remain on the pallet or stack for more than a few hours. The presence of
mildew and distinct yellowing of the leaves is usually good evidence of reduced
turf vigor from being stacked too long.
To lay the sod, start with a straight edge such as a driveway or sidewalk.
Unroll sod pieces tightly against each other, but don't overlap. Lay the pieces
in a staggered, bricklike pattern. Using a sharp knife, cut pieces to fit curves
or small areas. After the sod has been laid, roll it to ensure good contact
with the soil. Be sure to water thoroughly, and water every day during dry,
warm weather. Avoid soggy situations.
Watering
Newly seeded or sodded lawns require special irrigation. A newly seeded lawn
requires daily watering and may need as many as four light waterings in a single
day if conditions are dry and windy. Keep the seedbed moist, but not saturated,
to a depth of 1 to 2 inches until germination occurs (green cast to lawn and
seedlings 1/4 to 1/2 inch tall). At this stage it is crucial that seedlings not
be stressed to the point of wilt.
Continue to water one to four times a day with light applications, approximately
1/8 to 1/4 inch of water per day. Straw applied at the time of seeding helps
to shade the soil and to prevent rapid drying of the soil surface. It will also
reduce soil erosion and seedling damage from the force of large sprinkler drops.
Watering with a light mist is best for establishing new lawns. As seedlings
reach 2 inches, gradually reduce the frequency of watering and water more deeply.
Begin mowing once a week when the seedlings reach a height of 3 inches. After
the new lawn has been mowed two or three times, water deeply and infrequently.
Newly sodded lawns may require watering one or two times a day. Begin irrigation
immediately after laying sod. Plan your sodding operation so that a section
of laid sod can immediately be watered while other areas are being sodded. Sod
should be watered so that the sod strip is wet as well as the top 1 inch of
soil below the sod.
The first irrigation requires about 1 inch of water to achieve complete wetting
of the sod. After watering, lift up pieces of sod at several locations to determine
if it has been adequately irrigated. Continue watering one to two times a day
or as needed with light irrigations to prevent wilting and to ensure a moist
soil just below the sod layer. As sod becomes established and roots penetrate
and grow in the soil, gradually reduce the frequency of watering but wet the
soil deeper. After sod has been mowed two or three times water deeply and infrequently.
During hot, windy conditions, establishing sod may require several light
mistings per day to prevent wilt and potentially high lethal temperatures. In
this case, mist the sod lightly just to wet the leaf surface and not to supply
water to the soil. Misting cools the grass plant as water is evaporated from
the leaves.
Do not over-irrigate the soil because that will inhibit sod roots from growing
into the soil. In situations where daily watering is not possible, thoroughly
water the sod and soil to a depth of 6 inches. This will delay the rooting time
of sod but will reduce the chance of rapid drying and severe loss of grass.
Control weeds
Spring seeded cool-season grasses
Even though spring seeding of cool-season grasses is not as successful
as fall seeding, spring and early summer seeding may be unavoidable. Some tips
may help your attempt to establish cool-season grasses.
- Seed as early as possible. In Missouri, wet spring conditions may prevent
using equipment, especially on construction sites. Prepare soil and spread
seed in February or March if conditions are dry. Seeds will lay dormant until
warm April temperatures cause germination.
- Consider using a slit seeder or drill that causes minimal surface disturbance.
This reduces competition from weed seeds that may be brought to the surface
with complete tillage. These types of seeders are available from rental services
or lawn care professionals.
- Competition from crabgrass is a major problem with spring seeding, especially
when the lawn is seeded with mostly Kentucky bluegrass. Siduron (Tupersan)
is the only preemergent crabgrass herbicide that can be used with new spring
seedings, and it will not harm the planted turfgrasses as they emerge. It should
be applied as the final operation after seeding and before crabgrass germination.
If lawn grasses are seeded in February or March, wait until early April to apply
siduron so that crabgrass control will last longer into the summer. Shaded
areas of the lawn do not need crabgrass control.
- After three or four mowings, usually at least a month after grass emerges,
a label-recommended
rate of a broadleaf herbicide on actively growing grass if broadleaved weeds appear
to be overpowering the grass. Do not use herbicides if you do not have a serious
weed problem -- frequent mowing and proper starter fertilizer may be the only
management necessary to establish grass. Broadleaved weeds can be easily controlled
during the following year, provided the turf is able to initially establish
without being crowded out by weeds.
- Use slightly higher seeding rates to ensure rapid cover and improve
competition with annual weedy grasses. Perennial ryegrass, because of its rapid
germination, stands the greatest chance of filling in during the first year.
Tall fescue is the next best choice for showing at least a modest stand of
grass by the fall. Kentucky bluegrass requires two to four weeks to germinate
in the spring. It usually develops a modest stand of grass in the spring. Never use more than 20
percent perennial ryegrass in a mixture.
| |
Higher -- spring seeding rate |
Normal -- fall seeding rate |
| Kentucky bluegrass |
3 pounds per 1,000 square feet |
2 pounds per 1,000 square feet |
| Perennial ryegrass |
10 pounds per 1,000 square feet |
7 pounds per 1,000 square feet |
| Tall fescue |
10 pounds per 1,000 square feet |
7 pounds per 1,000 square feet |
Fall seeded cool-season grasses
Fall seedings are much more successful than spring seedings because
crabgrass and summer stress are not a problem. However, winter annual broadleaved
weeds such as henbit, chickweed and speedwell may require control. These weeds
germinate September through November, grow during the winter and result in a
dense mat of weeds by early spring.
If weeds dominate the new lawn in the fall, use a postemergence herbicide after the lawn has been mowed at least three times, usually about
45 days after grass germination. Apply broadleaf herbicides on a warm sunny
day in the fall when no frost is expected. If needed, winter annual broadleaved
weeds can also be killed in late March and April. Even though these weeds naturally
die in May, without herbicide application, they should be controlled in early
spring if they are overly competitive.
If annual broadleaved weeds are left uncontrolled, turf will appear thin
and weakened through the summer in areas where weeds have naturally died.
Lawn renovation
Lawns may occasionally thin out and become weedy as the result of poor management,
pests or severe summer stress.
Lawns that do not need regrading or soil tilling may be renovated by simply controlling
weeds, planting seed and fertilizing. Also, determine the cause of lawn decline
so that you can adjust your lawn care program.
Establishment practices mentioned above for time of seeding, weed control,
fertility and watering also apply to renovation.
General steps to renovate turfgrass
- Control existing vegetation that you don't want. If you use a selective
broadleaf herbicide (2,4-D, dicamba, or mecoprop), wait one month before
the next step. Proceed after seven days following total vegetation
control with Roundup herbicide and five days with Finale
- Set your mower as low as possible, scalp off all existing vegetation, and
rake clean
- Prepare surface with power rake, verticutter or core aerifier. Skip steps
4, 6 and 7 if you use slit seeding equipment, which places seed directly
into the soil
- Rake loosened thatch and existing debris
- Add fertilizer
- Make a final pass to create open channels for seed collection
- Apply seed in two directions
- Lightly rake seed into soil surface
- Water frequently until established
Renovating tips
Assess situation
First, assess your lawn situation for desirability and appropriateness
of the grass, presence of weeds and bare spots. Kill existing vegetation (grasses
and weeds) if any one of the following apply:
- Less than 50 percent of the area is in the desired turfgrass
- Only a cool season lawn grass is desired but bermudagrass has invaded. If
bermudagrass is in localized patches or is encroaching from a neighbor along
your property line, kill all vegetation only in those areas
- You want to use a turf-type tall fescue but currently have Kentucky bluegrass,
or K-31 tall fescue
- You have several weeds that require non-selective control such as quackgrass,
tall fescue, bermudagrass and nimblewill.
Lawns that have more than 50 percent desirable
grass, but still appear thin and weak with several
broadleaved weeds, may need only control of
broadleaved weeds with broadleaf herbicides. After
weed competition is reduced, lawns may regain their
original density.
Bare patches less than 4 inches in diameter likely will fill in on their
own with proper fertility and no additional seeding. Larger areas that remain
too thin a month after broadleaf herbicide treatment may be overseeded. Shaded
areas of lawns with thin turf and exposed soil often appear to need additional
seeding. Renovate these areas but do not kill existing turf that has thus far
survived the difficult growing conditions of shade.
Prepare surface for seeding
One of the most important steps in renovation is placing the seed in
contact with soil. This sounds simple, but most lawns have thatch - an intermingled
layer of both dead and living plants - over the soil surface. This brown, decomposing
layer may be up to 1-1/2 inches thick. Lawns with more than 1/2 inch of thatch should
be dethatched.
Seed placed on or in the thatch layer may germinate, but the eventual stand
of grass that develops will be poor. To ensure good seed-to-soil contact,
use power equipment to prepare the surface for seeding. Power rakes, verticutters,
slit seeders and core aerators are effective machines for properly preparing
the surface for seeding.
Dethatching equipment is sometimes available from local rental stores. Local
lawn care and landscape companies also provide dethatching and renovation service.
Two to four passes over the lawn may be necessary depending on the soil hardness
and thatch thickness. Raking of excess debris will be necessary as well.
Power rake
Power rakes are lawn mower-like machines that have spring tines instead
of blades. The
power-driven spring tines rotate in a vertical position
and pull the thatch to the surface.
Spring tines that attach to the lawn mower blade do not adequately prepare
the surface for seeding. A half inch of thatch can be removed with a severe
power raking, but be prepared to handle several bags of loosened thatch. Power
rakes that can be adjusted so that the soil surface is slightly scratched will
ensure good seed-to-soil contact but may not loosen hard soils.
Vertical mower
Vertical mowers are similar to power rakes except that they have fixed
or flail-type blades that cut groves through the thatch and into the soil. Fixed-blade
vertical mowers, sometimes called slicers, are better at cutting into the soil.
Heavy-duty, walk-behind vertical mowers are superior to power rakes for preparing
a seedbed. They cut deeper into the soil, 1/2 to 3/4 inch, redistribute some
soil onto the surface, and provide some soil loosening that helps seedling establishment.
Power rakes and vertical mowers can accumulate a large amount of grass debris
on the surface that should be removed so that the seed can contact the soil.
After sufficient disruption of the surface, lightly rake the dead debris off
the surface, leaving the loosened soil behind. After raking, a final pass with
the equipment will produce closely spaced groves that are excellent channels
for catching broadcast seed.
Slit seeder
Slit seeders are smaller versions of agricultural grain drills, but
with closer spacings between discs. The discs slice open the ground just ahead
of a small tube that drops the seed into the open furrow. A packing wheel follows
the seed tube and closes the sliced ground.
Some slit seeders also have a vertical mowing attachment in front of the
discs that loosens and redistributes soil on the surface. A slit seeder sows
grasses in distinct rows 2 to 6 inches apart depending on the space between
the drill discs. It is important to repeat the seeding process at different
angles. This usually
can be accomplished with two to four passes across the lawn making a checkerboard
pattern.
Core aerifier
Coring machines have a series of hollow tines that cut several cylindrical
holes in the ground 2 to 3 inches deep and 1/2 inch in diameter. Some machines
will not penetrate hard and dry compacted soils.
Coring machines are primarily used to provide a channel through which air,
fertilizer and water can enter the soil. This channel cut through the thatch
and into the soil helps to reduce soil compaction, increase root growth and
redistribute soil on the upper surface of the thatch. The soil should be sufficiently
moist so that the coring machine can penetrate. If a screwdriver can be pushed
by hand 3 inches into the ground, the soil is about right. Soils that are too
wet will clog the hollow tines and prevent core removal.
The soil cores should be left on the surface to create a more favorable environment
for breakdown of the thatch layer by naturally occurring soil microbes. When
the soil cores have dried, they can be chopped and dispersed over the surface
with a mower, verticutter or power rake. If coring is to be the primary means
of preparing a seedbed, the area should be cored to produce at least one hole
every 2 inches. Seed and fertilize while the core holes are open.
Core aerifiers are of many different sizes and shapes. As with all equipment,
check to see that it will fit through the gates on property gates before renting
or contracting a service.
G6700, reviewed March 2003