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Richard L. Duble, Turfgrass Specialist
Texas Cooperative Extension
Text and images copyright © Richard Duble.
Mowing is the primary cultural practice in turf management. Without regular
mowing even a fine turf quickly becomes just another weed patch. Good mowing
practices enhance a sports turf more than any other cultural practice. Density,
texture, color, root development, wear tolerance and other aspects of turf
quality are all enhanced by proper mowing.
Mowing is primarily a function of the growth rate of grasses. Since grasses
continually interact with their environment, the growth rate changes in
response to environmental changes. Thus, the turf manager must recognize
the need to change mowing practices accordingly. For example, during prolonged
periods of drought stress, it might be advantageous to raise the mowing
height and reduce the frequency of mowing. Similarly, following the application
of fertilizer, it may be necessary to increase the frequency of mowing to
avoid excess accumulation of leaf clippings. The skill of the turf manager
at making these adjustments determines the quality of turf maintained under
Although growth rate largely determines the mowing schedule for a particular
site, other factors need to be considered when planning mowing practices.
The type and size of mower, frequency of mowing, mowing height, mowing patterns,
the management of grass clippings and the maintenance of mowing equipment
all need to be considered when planning mowing practices.
The type and size of a mower is important to the quality of cut produced
and the frequency of cut likely to be achieved. A common reason for shortened
life span and high maintenance costs of mowing equipment is the use of a
mower in an area and in a situation for which it was not designed. The problem
is compounded when a poorly trained or incompetent operator is assigned
to run a unit unsuitable for the job. When choosing equipment:
Variations in terrain on which the mower is used, the type of lubrication
it receives, the correctness of repair, the treatment by the operator, storage,
and accuracy of records, all have an influence on cost per mower per year
and useful life span of the mower. However, to get the lowest possible operating
costs under your conditions, buy quality equipment, buy the right mower
for the job, operate and maintain it properly and keep adequate records.
- Consider the terrain to be cut. Is it developed or undeveloped? Is
it wooded, rough graded, stony, swampy, hilly, of a formal area? If rough
or otherwise, decide if a reel or rotary type mower is to be purchased.
- Consider the size of the area or areas and buy the largest mower that
is practical. The job gets done faster-with less man hours-when larger capacity
equipment is employed. If the mower is to be used for trimming purposes
and demands on the mower are not too heavy, a small, low horsepower, light
duty unit may be used, but higher maintenance costs on this type of equipment
- Look for simplicity of design. A complicated mower may be difficult
to adjust and a trained expert may have to be used for repair.
- Check for construction, durability and maneuverability. The mower
should be substantially built, well-braced and have good bearings. The sideframes,
handles or drawbars should be heavy enough to do the job. The bed bars,
reels and blades, should be rigidly constructed. And it should be highly
maneuverable and easy to steer.
Other points to consider when selecting and operating equipment efficiently
and at lower total costs include:
The two basic types of mowers are the reel and the rotary mower. The reel
mower consists of a shaft equipped with blades rotating between two wheels
with a stationary bedknife. The grass blades are cut, or sheared, as they
are caught between the reel (blade) and the bedknife. A properly adjusted
reel mower cuts the grass just as cleanly as a sharp pair of scissors.
- Labor. Over the past several years, the greatest increase in
cost for turfgrass maintenance has come from labor. In fact, labor comprises
the largest part for the total budget, and the costs of labor are growing
as fast or faster than those for equipment. Because of this, turf managers
must continue to look more closely at total costs and allocate more of their
funds for the purchase of higher capacity, labor-saving equipment.
- Reel Mowers. Generally, the reel mowers are more efficient
than rotary or flail mowers. The scissors action of the reel mower not only
cuts better but requires less power, consequently consuming less fuel. At
the same mowing speed, reel mowers will use up to 50 percent less fuel per
acre of cut grass than rotary mowers. The number of blades per reel also
affects the quality of cut, and impacts fuel-consumption. For example, a
five-bladed reel will use 8 to 12 percent less power and fuel than a six-bladed
reel. However, determining the quality of cut for a given area which in
this case is primarily a function of the height of cut, is the responsibility
of the turfgrass manager. It is up to him to decide whether the economy
achieved by raising the height of cut and using fewer blades will produce
the quality of turf required.
- Diesel Engines. Diesel fuel costs less and the diesel engine
has proved itself to be from 20 to 25 percent more efficient than the gasoline
engine. This means fewer gallons and less dollars to perform a given task.
The increase in efficiency with resultant lower total cost may be sufficient
reason to consider diesel power when selecting and purchasing new equipment.
- Equipment Maintenance. Clean and properly adjusted equipment
is more economical to operate because less power is required to operate
such equipment. Proper adjustment of belts, bearings, chains and shafts
can reduce the friction within the mower, allowing for more power for work
output. Frequent lubrication of vital parts also reduces friction.
- Storage. Proper storage of equipment plays an important role
in saving money and reducing total costs. When a job is finished and the
unit properly cleaned, the operator should then store it in a clean and
dry area. Without adequate storage facilities, total costs for equipment
are likely to be excessive.
A rotary mower consists of a horizontally rotating steel blade which cuts
the grass by impact at a high rate of speed. The rotary mower cuts the grass
much like a sickle. So long as the blade is sharp, the quality of cut can
be quite good. But a dull blade shreds the leaf blade and leaves the leaf
tip frayed. Although rotary mowers are relatively inexpensive and more versatile
than the reel mowers, they do not cut as cleanly or as close as the reel
On closely mowed turf such as that on sports fields, golf greens, fairways,and
some lawns, the reel mower provides the best cut. However, the quality of
cut is influenced by the mowing height, the number of blades on the reel,
the rotational speed of the reel and the forward speed of the mower. The
typical reel mower has 5 to 7 blades and is suitable for mowing at heights
of 0.5 to 1.5 inches. At lower mowing heights, the turf would develop a
wavy or rippled appearance unless the reel was powered to revolve at a high
rate of speed. At mowing heights below 0.5 inch, 9 or more blades per reel
or a hydraulically-powered reel are required to produce a smooth cut. The
typical golf green mower has 11 to 13 blades on a relatively small diameter
The "clip" of a reel mower is most readily defined as the "distance"
the mower moves forward between the time that each reel blade engages the
bedknife. Most conventional homeowner type reel mowers have a clip of about
one inch. For optimum smoothness of cut with respect to ripple or corrugations,
a reel-type mower should have a clip approximately equal to the height of
cut. Ground-driven reel mowers have a constant clip and can only provide
a smooth cut above a specific height and will show obvious ripples below
that height. Power or hydraulic driven reels provide a variable "clip"
and extend the application of a given reel mower.
Vertical differences between the peaks and valleys of a reel cut are always
present because the "valley" is the height of the bedknife cutting
edge and the "peak" is the height to which the grass springs back
after being cut. The horizontal distance between peaks, or between valleys,
is the clip. When the vertical distance between the peak and valley is minimal
the resulting cut will "appear" to be smooth. Again, this condition
exists when the clip is no greater than the height of cut.
The specific clip of a reel mower is dependent upon the number of blades
and the rotational speed of the reel and is independent of reel diameter.
The tip speed, however, does increase in direct proportion to an increase
in the reel diameter when rotation speed is constant.
If we consider a reel with a certain number of blades, the "clip"
can only vary with the rotational speed of the reel in relation to ground
speed. With the same number of blades, the faster reel will produce the
shorter clip length.
The relationship of "clip" to "height of cut" affects
not only the finished appearance of the turf, but the ability of the mower
to cut at heights of two or three times the clip distance. A mower with
a 1-inch clip will not cut as well at a 2-inch height as a mower with a
There are three basic requirements for acceptable reel mower performance
: (1) the bedknife must be exactly parallel with the reel; (2) the reel
must make only light contact with the bedknife and (3) the cutting edges
of the reel and bedknife must be sharp and straight. A sharp, properly adjusted
mower will cleanly cut a piece of paper. Backlapping is the standard procedure
used to restore sharp edges on the reel and bedknife.
From time to time, either in the field or after reel service, it may become
necessary to reconfirm the reel to bedknife contact. Newspaper can be used
to help measure the degree of contact along the length of the bedknife.
By placing the paper tangent to the reel cylinder between the blade and
bedknife, the paper can be used as shim to bring each of the reel blades
in equal contact with the bedknife. The paper should be pinched, but not
cut. Next, place the paper perpendicular to the reel cylinder and refine
the adjustment to just cut the paper. Check at least 3 points along the
length for each blade.
At taller mowing heights, 1.5 inches and more, the rotary mower is generally
used. At these taller heights, the quality of cut may not be as important
and the rotary mower cuts tall grass, weeds and seedstalks more effectively
than the reel mower.
The rotary mower cuts grass by impact of the blade against the grass at
a very high velocity. The first one half inch of the blade's leading edge
cuts the grass. The additional cutting edge length enhances the mowing performance
and quality of cut.
Theoretically, the concept of clip also applies to rotary mowers. Rotary
mowers are generally designed so that the blade tip cuts the grass at least
once every two inches.
In addition to the cutting performance of the rotary blade, good dispersion
of grass clippings is also important. Good dispersion is determined by the
blade speed, blade design, housing depth, baffling and other factors that
affect airflows and velocities.
From the point of view of the blade, there are three irregularities which
can decrease quality of cut. These regularities are a warped, twisted, or
dull blade. A warped blade is bent in such a way that the blade tips are
worn on one or both sides. The situation must be corrected. The twisted
blade leaves the cutting edge above the flat surface it is being checked
on. With the body of the blade parallel to the flat surface, the blade edges
should lay flat on the surface. A twisted blade consumes additional horsepower,
and causes shredding of the grass blade tips.
To properly sharpen a rotary blade, material should be removed from the
top surface of the blade only, trying to maintain the original bevel. If
the lower edge of the blade is ground or filed, the cutting edge will be
above the heel of the blade, resulting in beating, shredding and browning
of the grass.
In addition to blade irregularities, damaged housing or improperly mounted
engines or decks, bent crankshafts or spindles will result in uneven heights
Another impact-type cutting unit is the flail mower. The cutting unit on
a flail mower consists of a number of small blades attached to a horizontal
shaft. As the shaft rotates, the blades are extended by centrifugal force.
Each blade becomes an independent, freely revolving, cutting unit. Thus,
if the blade strikes a hard object, such as a rock or piece of metal, the
blade recoils without damaging the mower or creating a dangerous projectile.
The quality of cut still depends on the sharpeness of the blade.
Frequency of Mowing
The single most important aspect of turf management is the frequency of
mowing a turf. If there is a "secret" to turf management, it is
frequent mowing-the more often, the better. However, mowing is time consuming
and expensive. Therefore, we often compromise between what is best and what
Golf greens exemplify fine turf and are usually mowed daily. But, those
that are mowed twice daily are even finer. However, golf greens make up
only a small percentage of the total acreage of a golf course and efficient
mowing equipment makes frequent mowing practical. Fairways, however, constitute
a large percentage of a golf course and more expensive equipment and greater
time is required to mow fairways. Thus, fairways are not mowed as often
as greens. That doesn't change the fact that fairway turf would be better
with daily mowing.
Likewise, the sports field manager who mows his fields three or more times
per week will have a finer turf than one who mows less often. The same can
be said for the homeowner. The homeowner who mows every 5 days will have
a finer lawn than the one who mows at 7 to 10 day intervals.
Several factors influence the recommended mowing frequency. Of course, growth
rate (and factors that affect growth rate) and mowing height have the greatest
influence on mowing frequency. As a "rule of thumb", mow often
enough so that no more than 30 percent of the leaf is removed at any one
mowing. By following that rule, photosynthesis is only marginally affected
by mowing. However, if 50 percent or more of the leaf is removed by mowing,
several days are required to restore photosynthesis to its previous level.
In contrast, if only 10 percent of the leaf is removed by mowing, the effect
on photosynthesis is insignificant. Therefore, to maintain optimum growth,
frequent mowing is required.
In addition to minimizing the effect of mowing on photosynthesis, frequent
mowing also helps to maintain a high percentage of the leaf surface-a requirement
for healthy root development. Following severe defoliation (as a result
of infrequent mowing) energy reserves (food) stored in the grass plant are
needed to restore leaf surface. Consequently, root growth may cease for
several days since leaves always take priority over roots for energy reserves
following defoliation or dormancy. Thus, mowing frequency, which determines
the extent of defoliation, has a significant impact on residual leaf surface
and root growth.
Growth rate and mowing height must both be considered when deciding on a
mowing interval. If we follow the "rule of thumb" and remove only
30 percent of the leaf surface, the lower the mowing height, the shorter
the interval between mowing. For example, consider a growth rate of 0.1
inches per day and a mowing height of 1 inch. In 10 days the grass will
be 2 inches tall. Then, the mower would remove 50 percent of the leaf when
cut back to 1 inch. The turf would need mowing at 5 day intervals to stay
within the "30 percent rule of thumb". The same grass mowed at
.5 inch would need mowing at 2 or 3 day intervals to stay within 30 percent.
Without exception, the shorter a grass is mowed, the more frequently it
must be mowed.
Besides mowing frequency, the turf manager's use of fertilizer has more
affect on growth rate than any other cultural practice. High rates of nitrogen
fertilizer promote vegetative growth beyond that needed for maintenance.
Thus, mowing frequency must be increased as the application of nitrogen
increases. During summer months, nitrogen fertilization should be kept at
a maintenance level.
Environmental factors also influence mowing frequency through their effect
on growth rate. Temperature is the environmental factor that has the greatest
impact on growth rate. When temperatures favor growth, mowing frequency
needs to be increased. Conversely, when temperature retards growth, mowing
frequency can be reduced.
In warm season grasses, growth (leaf extension) begins at about 65°F.
As temperatures increase above 65°F, the rate of leaf extension increases,
assuming other requirements (light, moisture, nitrogen, etc.) are met. Consequently,
mowing frequency needs to increase as the season progresses from early spring
to mid-summer. To compensate for the increased growth rate and maintain
the same mowing frequency, mowing heights are raised as the season progresses.
The photoperiod (daylength) also influences mowing frequencies. During summer
months (long days) leaf growth is upright; while during spring and fall
(short days) leaf growth is more decumbent. Consequently, mowing frequencies
can be reduced during spring and fall months.
Grass variety and turf use have the greatest influence on mowing height.
Other factors such as mowing frequency, shade, mowing equipment and the
season of the year need to be considered, but grass variety and turf use
are the limiting factors. Tall fescue, for example, performs best at mowing
heights between 2 and 3 inches. Tifdwarf bermudagrass and creeping bentgrass
perform best at mowing heights below .5 inch. In general, the bermudagrasses
perform best at mowing heights of 1 inch or less, while other warm season
turfgrasses perform best at mowing heights of 1 to 2 inches. For the cool
season grasses, bentgrass performs best at mowing heights of .5 inch or
less, while bluegrass and ryegrass performs best at a 1 to 2 inch mowing
The parameters that determine mowing heights for grasses are often fixed
by the use of the turf. Golf greens, for example, must be mowed below .25
inch to provide the smooth, consistent and fast surfaces that golfers expect.
Sports turf for baseball, football, and soccer needs to be mowed near the
1-inch height to reduce interference with the ball and provide fast playing
surfaces. Grass bowling greens and tennis courts must also be mowed very
short. In contrast, roughs on golf courses are typically mowed at a 2 inch
height to penalize the golfer for hitting into the rough.
Grass areas that are mowed infrequently, but where appearance is important,
must be mowed between 3 and 4 inches in height to prevent scalping. Roadsides,
lawns around commercial and industrial sites, and some park areas often
meet these requirements.
On lawns, grass species, frequency of mowing, shade and the type of mower
determine the optimum height. The turf manager must realize that the shorter
a turf is mowed the more often it must be mowed to prevent scalping. As
a result, the homeowner may compromise between the height best suited for
the grass and the height best suited for his frequency of mowing. For example,
bermudagrass provides the finest turf at mowing heights below 1 inch which
requires mowing at 5-day intervals or less. If the homeowner can only mow
on a 7-day schedule, the mowing height must be raised to 1.5 inches to prevent
On shaded sites, mowing heights need to be raised 30 to 50 percent to compensate
for the more upright growth of leaves under reduced light. Grasses growing
in shade typically have long, thin, spindly leaves and higher mowing heights
help maintain leaf surface to carry on photosynthesis. If shaded lawns are
continuously mowed short, the grass gradually thins out and weeds invade
The type of mower the homeowner uses may also influence mowing height. Rotary
mowers do not usually cut below a 1-inch height and perform best at heights
between 1.5 and 3.0 inches. On the other hand, the reel-type mowers cuts
best at 1.5 inches or less.
The season of the year may also influence recommended mowing heights. In
early spring, close mowing is recommended to control thatch and to increase
turf density. Also, the more prostrate (decumbent) growth habit of grasses
in the early spring allows for close mowing. Mowing heights may be raised
slightly during summer months to reduce the frequency of mowing and to reduce
watering. Higher mowing heights in the summer also help compensate for the
more upright growth of leaves during long days. Mowing heights may be raised
again in the fall on warm season grasses to reduce the risk of winterkill
from low temperatures. Then, in the spring as the grass breaks dormancy,
the lower mowing heights may be used to remove excess residues and promote
early green up.
Using St. Augustine grass as an example, the homeowner may mow the lawn
at 1.5 inches in early spring to remove excess residues and promote early
recovery of the lawn. By mid-summer the mowing height might be raised to
2.0 to 2.5 inches to reduce mowing frequency. Finally, in areas of the South
where winterkill occurs, the mowing height might be raised to 3 inches in
the fall to provide more cover and insulation for the stolons and crowns
of St. Augustine grass during winter months.
Mowing patterns are often neglected, but they, too, can have a significant
influence on turf quality. Lawns that are mowed in the same pattern each
time because of convenience develop problems during stress periods. If grass
clippings are not collected from such lawns, clippings tend to accumulate
in rows along the path of the mower. During severe drought or cold stress
the thatchy rows are the first to show injury. By changing the mowing pattern
each time the lawn in mowed, the grass clippings are uniformly distributed
and the problem does not develop.
On golf courses and sports turf mowing along the same path and direction
each mowing produces grainy turf and non-uniform playing conditions. Even
on golf course fairways where it is most convenient and much faster to mow
the length of the fairway, it is advantageous to occasionally mow across
the width of the fairway.
Mowing the same direction between alternate yardage stripes on a football
field may be done for the visual effect, but the direction should be reversed
occasionally. Likewise, mowing a baseball field or golf green in a checkerboard
pattern is fine for the effect it produces, but the direction of mowing
should be occasionally reversed.
Management of grass clippings is critical to the quality of turf produced.
On very dense, closely mowed turf areas such as sports fields and golf greens,
grass clippings are routinely removed for aesthetic purposes and to prevent
interference with the ball. On turf areas mowed at .5 inch or higher, clippings
do not need to be removed if they do not interfere with the use of the turf.
If the turf is mowed at appropriate intervals and clippings are uniformly
dispersed, the clippings do not present a problem. In fact, by leaving the
clippings in place, the nutrients they contain are recycled through the
turf and the need for fertilization is significantly reduced. By catching
and discarding grass clippings each time a turf is mowed, about 100 to 150
pounds of nitrogen per acre are removed each year.
On large turf areas where it is not practical to remove clippings it may
be necessary on occasion to mow several times in one day or several days
in a row to uniformly disperse the clippings. This is often necessary following
several days of rain or following an application of fertilizer. Grass clippings
should not be left in such volume that appear unsightly or smother the grass.
If a homeowner does not want grass clippings left on the lawn, they can
be used for compost in a garden or as a mulch around plants. But, other
than for aesthetic purposes, there is no need to routinely remove grass
clippings from lawns.