Title: Vertical mowing of warm-season grasses
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 Material Information
Title: Vertical mowing of warm-season grasses
Series Title: Vertical mowing of warm-season grasses
Physical Description: Book
Creator: Meyers, Harry George,
Publisher: Florida Agricultural Extension Service, Institute of Food and Agricultural Sciences, University of Florida
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Full Text
CIRCULAR 314


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VERTICAL MOWING OF

WARM-SEASON GRASSES
HARRY MEYERS


FLORIDA AGRICULTURAiETENSIO S
INS* T*ITU O FO A ARi FT ARI LTUL SE
UNIVER SITY OF FLOIGANESILLE


JUNE 1967





VERTICAL MOWING OF WARM-SEASON GRASSES
Harry Meyers
Assistant Ornamental Horticulturist


Vertical mowing of warm-season
grasses is necessary due to thatch
build-up. Thatch is a natural lay-
ering of dead and dying stems,
stolons, leaves and rhizomes which
is peat-like in nature and accumu-
lates between the visible green grass
and the soil (Figure 1). It restricts
downward movement of air, water
and fertilizers and creates an ideal
breeding place for i n s e c t and
disease organisms. Thatched grass
is spongy, wilts rapidly in dry
weather and has a tendency to die
out in patches or large areas over
a period of time. Heavily thatched,
spongy lawns are easily scalped
during mowing and may turn
brown before they recover.
Thatch can be removed by verti-
cal mowing but experience with the
method and a knowledge of the
grass being renovated is necessary
to prevent additional damage to
the turf. Vertical mowing is a
method of cutting grass vertically
which requires use of a specialized
mowing machine. A typical verti-
cal mower utilizes evenly spaced


GREEN GRASS ... .:.:.'".
BLADES
THATCH AREA--- I lL W 4
SOIL-


knife blades mounted vertically on
a steel shaft which revolves at high
speed (Figure 2).
Vertical mower blade spacing
suggestions for various grasses are
given in Table 1. These spacings
are based on internode lengths of
the various grasses and on presence
or absence of rhizomes. Spacings
may be varied from those given in
Table 1, but such deviations are
not recommended without
thorough familiarity with the
grass and with vertical mowing.
Thatch removal increases as
depth of cut increases until soil
penetration occurs. Depth of cut,
regardless of grass or suggested
blade spacing, should be set to the
soil line for maximum effective-
ness. However, soil aeration and
lessened soil compaction may be
obtained if sufficient power is avail-
able to include soil penetration. If
power is limited, depth of cut
should be as deep as possible with-
out overloading the engine.
Grasses are normally vertically
mowed twice for best results dur-




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FIGURE 1. Bermuda grass: 1-Green grass blades; 2-Thatch area; 3--soil.
Acknowledgement to Dr. G. C. Rorn, Associate Turf Technologist, for reviewing
this manuscript.







































FIGURE 2. Lightweight vertical mower showing evenly spaced cutting blades.


ing renovation, the second time at
right angles to the first. The
operator has the responsibility of
knowing when to stop vertical
mowing if the grass has to be ver-
tically mowed more than twice due
to excessive thatch, a lightweight
vertical mower or for other rea-
sons.
Bahia, z o y sia and bermuda
grasses are rhizomatous and may
be vertically mowed in several di-


reactions without fear of killing the
turf (Figure 3). Rhizomes are
modified stems which grow hori-
zontally at or below ground level
and help promote new top growth
after vertical mowing. Bahia,
zoysia and bermuda grasses verti-
cally mowed in several directions
require approximately 30 days for
full recovery during the growing
season (Figure 3).
Centipede and St. Augustine-










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FIGURE 3. Bermuda grass: Grass on left has not been vertically mowed. Grass on
right has been vertically mowed, scalped, and trash removed.


grass do not possess underground
rhizomes but spread by means of
above-ground stolons or runners.
Centipede and St. Augustinegrass
stolons grow in layers over the soil,
producing sod which eventually
forms a heavy thatch. During ver-
tical mowing all but the last layer
of live runners may be removed
(Figure 4). Removal of all live
runners will kill centipede and St.
Augustinegrass since there are no
underground rhizomes to help pro-


mote reestablishment. The basic
problem in vertically mowing these
two grasses is to remove as much
thatch as possible during the
process of eliminating all but the
last layer of live runners. The de-
gree of renovation just described is
the most severe that can safely be
used on centipede and St. Augus-
tinegrass without killing them and
may require 30-90 days for full re-
covery. These grasses should be
vertically mowed more than once,


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FIGURE 4. St. Augustine grass: Grass on left has not been vertically mowed.
Grass on right has been vertically mowed, scalped, and trash removed.
Note remaining green, live runners.


permitting full recovery between
renovations if thatch accumulation
exceeds approximately 2 inches.
WHEN TO VERTICAL MOW.-
The best time to vertical mow
grasses south of Orlando, Florida,
is from May through July when
they are growing most rapidly and
thus will recover most quickly.
North of Orlando, grass may be
vertically mowed during the same
period, but to avoid additional
browning which usually follows


vertical mowing, grass in this area
may be vertically mowed in
February or March prior to the
start of active growth.
Vertical mowing thins turf and
may expose bare soil or disturb the
surface soil. Weed seeds brought
to the soil surface as a result of
this procedure, p lus air-borne
seeds, may be exposed to light and
moisture favorable for their ger-
mination. Early spring vertical
mowing of dormant grasses is pre-


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ferable to winter mowing since in
spring winter weed invasion is re-
duced and preemergent herbicides
can be applied for control of sum-
mer weeds.
Prior to vertical mowing any
grass, have soil tested for nema-
todes. If treatment is necessary
apply a nematicide 60 days before
vertical mowing.

FERTILIZATION. Renovation
by vertical mowing is a temporary
setback to actively growing grass,
reducing its ability to synthesize
plant food, due to removal of green
grass blades. Recovery is therefore
more rapid if the grass is growing
vigorously when vertically mowed.
With the exception of dormant
grass, growth can be promoted by
fertilizing with a complete fertili-
zer, such as a 16-4-8, 7 to 10 days
prior to vertical mowing. Apply all
fertilizers at the rate of 1 pound of
actual nitrogen per 1000 square
feet and water-in immediately fol-
lowing application. To determine
the number of pounds of mixed
fertilizer required to apply 1 pound
of actual nitrogen per 1000 square
feet divide 100 by the total per-
centage of nitrogen in the fertilizer
(the first number of the fertilizer
analysis). Example, apply 6.25
pounds of a 16-4-8 fertilizer per
1000 square feet.
Immediately after renovation of
actively growing grasses apply
water soluble inorganic nitrogen,
such as ammonium nitrate, at the
rate of 1 pound of nitrogen per
1000 square feet. Natural organic


fertilizers can be substituted for
this application of fertilizer on ac-
tively growing grasses to minimize
chances of worm infestation. Ap-
ply organic fertilizers at the same
rate as inorganic sources. St.
Augustinegrass fertilized with ni-
trogen from an organic source is
less susceptible to chinch bug at-
tack, and centipedegrass is less
susceptible to iron deficiency. A
third application of natural or in-
organic nitrogen at the same rates
as previously applied may be neces-
sary 2 weeks after severe vertical
mowing.
CLEANUP.-Sufficient thatch may
be removed from the average size
subdivision yard (7,000 square
feet) to overflow the beds of two
1/2-ton pickup t r u c k s. Thatch
brought to the surface as a result
of vertical mowing may be raked
up with rigid or spring lawn rakes,
but best results are obtained if
push-type or vacuum pickup
sweepers are used.
SCALPING.-Vertically mo wed
grass should be scalped with a reel
or rotary mower after debris has
been removed by raking or sweep-
ing. Consult Table 1 for appropri-
ate scalping heights. Grass
catchers should be used regardless
of type mower used, and all clip-
pings should be removed. Mowing
heights for all grasses should
gradually be increased during the
growing season to maintain con-
sistent good appearance (Table 1).
TOPDRESSING.-Topdressing to
level the yard or fill small depres-







sions may be desirable following
cleanup and scalping. Topdress
with soil similar to that on which
the grass is growing, since top-
dressing with soil that is dis-
similiar to the native soil produces
layering. Layering can result in
shallow root systems due to poor
water and air movement through
layers of different textured soils.
Topsoil should be sterilized before
application to prevent weed seed
germination and screened to re-
move foreign material such as
small twigs and rocks.


Never bury grass with topsoil
when leveling or filling depressions
since this will kill it. A rule of
thumb is never to apply topdress-
ing in excess of one-half the
scalped mowing height following
vertical mowing. Example: Up to
0.5 inch of topdressing may be ap-
plied to St. Augustinegrass since
its scalped mowing height is 1.0
inch (Table 1). Table 2 contains
volumes of topsoil required for
varying thicknesses of topdressing.
Thoroughly water-in all topdress-
ing material.


TABLE 1. RECOMMENDED BLADE SPACING AND MOWING HEIGHTS (in inches)
TO USE DURING AND FOLLOWING VERTICAL MOWING.
Scalped mowing Final mowing
Vertical mower height after height at end
Grass type blade spacing vertical mowing of growing season
Bahiagrass 1.0 1.0 3.0
Bermudagrass 1.0 0.5 0.75-1.0
Centipedegrass 1.0-1.5 0.75 1.0-2.0
St. Augustinegrass 2.0-3.0 1.0 2.0-2.5
Zoysiagrass 1.0 0.5 0.75-1.0



TABLE 2. VOLUMES OF TOPSOIL REQUIRED FOR TOPDRESSING
1,000 SQUARE FEET OF TURF AREA.
Inches of Cubic Cubic
topdressing feet yards
1/8 10 0.4
1/4 21 0.8
5/16 26 1.0
3/8 31 1.1
1/2 42 1.6
5/8 52 1.9
3/4 63 2.3
1.0 84 3.1



































































June 1967
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida,
and United States Department of Agriculture, Cooperating
M. O. Watkins, Director




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