The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
April 1986 Circular 668
G.W. Tanner, R.S. Kalmbacher and J.W. Pe 'a
Florida Cooperative Extension Service/ Institute of Food and Agricultural Scie
University of Florida, Gainesville / John T. Woeste, Dean for Extension
G.W. Tanner is Assistant Professor-Extension Range Specialist,
Dept. of Wildlife and Range Sciences, School of Forest Resources
and Conservation, Gainesville; R.S. Kalmbacher is Agronomist,
Dept. of Agronomy, ARC-Ona; and J.W. Prevatt is Associate Pro-
fessor-Extension Economist, Dept. of Food and Resource
Economics, Gulf Coast Research and Education Center; respec-
tively, Institute of Food and Agricultural Sciences (IFAS), Univer-
sity of Florida.
Saw-palmetto (Serenoa repens (Bartr.) Small) is a low growing shrub
found commonly on open and forested range throughout the extreme
southeastern portion of the United States. At present, this shrub
dominates much of the south Florida range and also is a dominant
understory component in the north Florida flatwoods. Although
preferred forage species growing under palmetto are protected from
overgrazing, overall forage production is lowered when saw-palmetto
dominates the site. In north Florida, the presence of saw-palmetto and
other shrubs impedes harvesting of existing pine tree stands and
necessitates the use of site preparation methods in order to re-
establish pine plantations.
Land managers have experimented and tested several means of saw-
palmetto control over the past several decades. Fire, mechanical
treatments, and herbicides have been employed alone or in combina-
tions. The intent of this publication is to summarize the results of
those experiments and to suggest better methods of saw-palmetto
management on range in Florida.
M 11 -
Figure 1. Saw-palmetto leaf and petiole.
Saw-palmetto is a member of the Arecaceae family. This shrub is
easily recognized by its mature palmate leaf (frond) and the
characteristic spiny-toothed margins on the leaf petiole (Figure 1).
Fronds are arranged in a terminal cluster on stems that usually are
partially or completely subterranean. Occasionally stems may
become erect or oblique to a height of 20 feet. Flowering occurs dur-
ing April to early May. Drupelike fruit develop during late June and
July and turn blue-black in color when mature in September and Oc-
tober. Summer also is the major time of frond production and growth.
Hilmon (1968) reported that an average of 5.4 fronds/plant/year were
produced in south Florida with frond longevity being between 18 and
Carbohydrate reserves of saw-palmetto are principally starch and
are stored in the stems (Hough 1968). These reserves follow seasonal
cycles which are influenced by phenological processes of winter dor-
mancy, frond growth, and flowering. Starch was highest in winter
(37%) and lowest in summer (27%) in stems of unburned plants in
Georgia. Kalmbacher, et al. (1983) reported a similar trend in total
available carbohydrates for unburned plants in south-central Florida.
When to Control Palmetto
The objective of controlling saw-palmetto is to reduce plant density
and canopy cover to allow desirable grass species to dominate. Recent
research at the Ona ARC studied the plant size when saw-palmetto
limited dry matter production of creeping bluestem (Schizachyrium
stoloniferum Nash, a preferred native forage found commonly on flat-
woods sites (Kalmbacher 1984). To answer this question, incident
sunlight was measured under palmetto canopies of various heights
before a March burn and throughout the following year (Figure 2). A
companion study measured creeping bluestem growth under shade
which blocked 25%, 55%, 73%, and 92% of the incident light and
made comparisons with growth in full sunlight. Forage yield de-
creased rapidly when light was less than 45% (Figure 3). This level of
shading within saw-palmetto plants occurred only after a height of 30
inches was attained. Therefore, it is suggested that saw-palmetto need
not be treated unless the plants are at least 30 inches in height.
A strong recommendation is that a site not receive any saw-palmetto
control treatment unless the rancher (1) knows that a sufficient quan-
tity of preferred, or decreaser, forage species is available to respond to
treatment and, (2) has developed a grazing plan to be implemented on
the site following the treatment. County Agricultural Extension Serv-
ice agents and/or the local U.S.D.A. Soil Conservation Service person-
80 60 cm
I-8 o 75cm
r o0 90cm
C- 0* 105cm
0 I --- p -I-
15 Mar 12Apr 15May 22July 9Sep 290ct 12 Jan 14 Mar
CALENDAR DATE, 1980-81
Figure 2. Percent incident sunlight measured at four heights within saw-palmetto canopy following a March burn. Source: Kalm-
o 1500 I
20 40 60 80 100
Figure 3. Forage yield of creeping bluestem as affected by artificial shading.
Source: Kalmbacher (1984).
nel can assist in identifying native forages and developing grazing
plans. Table 1 shows forage responses to several studies in which saw-
palmetto received mechanical control treatments. All four studies in-
dicated increases in decreaser forage biomass. However, the amount
of increase was quite variable, ranging from a 12.5 percent to a 25-fold
increase. Total forage biomass generally followed the same trend. The
cost of saw-palmetto control treatment must be paid for from in-
creased beef production on that site. Increased beef production can be
realized if the forage resource is improved, both in quantity and qual-
ity, and if the herd is managed properly according to the available
Florida ranchers traditionally have used fire on a three- to four-year-
cycle to remove dead forage and litter. Range burning usually occurs
in late winter when grasses are somewhat dormant, and when cool,
dry winds are more predictable. This allows for a greater degree of
Table 1. Herbaceous forage response following mechanical saw-palmetto control from selected studies in south Florida
2 through 5
Tanner et al.
1 through 3
1 through 3
1 Double chopping treatments except for Tanner et al. which was single chopped.
2 Decreaser forages are those species primarily chosen by cattle according to U.S.D.A. Soil Conservation Service guidelines. Biomass values are on a
dry weight basis.
3Only creeping bluestem separated as decreaser forage species.
fire control. The immediate responses are a reduction of shrub canopy
and an accelerated initiation of spring green-up of forages. Fire during
any season, however, is ineffective in killing saw-palmetto, which
will regain 80% of their crown coverage during the first year after a
fire (Hilmon 1968) (also see Figure 2).
Burning of saw-palmetto significantly affects the carbohydrate con-
tent in the plant (Figure 4). Summer lows in total available car-
bohydrate concentrations of burned plants are much less than in un-
burned plants, and the time required to replenish carbohydrate levels
is much delayed. Since burned saw-palmettos have a weaker energy
status than unburned plants, burning may predispose plants to greater
mortality if a subsequent chemical or mechanical treatment is ap-
Several herbicide formulations have been tested to determine their
efficacy of saw-palmetto control as indicated in Table 2. Herbicide
studies have typically compared various chemicals and rates, types of
carriers, month of application, and use of fire or mechanical
pretreatments as variables affecting the reduction of living saw-
palmetto plants. The herbicide 2,4,5-trichlorophenoxy acetic acid
(2,4,5-T) has received the most experimental use for which com-
parative data are available. Results of these studies indicated that
2,4,5-T applied at the rate of 2 to 4 lb/A (acid equivalent, a.e.) can give
saw-palmetto control ranging from 44 to 76%. Herbicide studies in the
1960s indicated that an oil-based carrier would not augment saw-
palmetto control over the 100% water carrier. Therefore, this rather
costly item need not be used.
Burning saw-palmetto prior to herbicide application was
hypothesized to weaken the plant by lowering carbohydrate reserves
and thus increasing the plant's susceptibility to herbicide action.
Although burning before treatment did increase plant kill in the
reported studies, the differences were not significant, as shown in
Table 2. Season of herbicide application appears to be the most impor-
tant factor affecting saw-palmetto control using 2,4,5-T. Both Burton
and Hughes (1961) and Kalmbacher et al. (1983) found saw-palmetto
control to be best when the herbicides were applied in summer.
At present no herbicides are approved by the Environmental Protec-
tion Agency (EPA) for use on pasture or range that are effective for
saw-palmetto control. Therefore chemical means of saw-palmetto
control cannot be recommended.
The two most common means of mechanical treatment used to con-
trol saw-palmetto are roller chopping (Figure 5) and web plowing
S I I I I I I I I I I I I I I I I I I i I I I
MAM J JASON D J F MA M J JASO N D J FM
1977 1978 1979
Figure 4. Total available carbohydrate in burned and unburned saw-palmetto rhizomes. Source: Kalmbacher et. al. (1983).
\ 4 A)1 '<- Burned
Table 2. Summary of studies using herbicides to reduce saw-palmetto plant density
Rate2 Carrier Month of
Authors Herbicide' lb/ac Water:Oil Application Preburn % Kill
Burton and Hughes
McCaleb et al.
Kalmbacher et al.
2.0,3.0, and 4.0
Table 2. continued
Rate2 Carrier Month of
Authors Herbicide' lb/ac Water:Oil Application Preburn % Kill
Kalmbacher et al. tebuthiuron 0,1.5,3.0,6.0 (a.i.) Yes 0
(1984) 0,1.5,3.9,6.0 (a.i.) No 0
S2,4,5-T = 2,4,5-trichlorophenoxyacetic acid; dalapon = 2,2-dichloropropionic acid; 2,4,5-TP 2-(2,4,5-trichlorophenoxy) propionic acid; 2,4-D -
2,4-dichlorophenoxyacetic acid; erbon = 2-(2,4,5-trichlorophenoxyl) ethyl 2,2-chloropropionate; tebuthiuron = N[5-(1,t-dimethylethyl)-1,3,4-
2 a.i. = active ingredient; a.e. = acid equivalent.
3 N/A no significant differences between carrier treatments and data averaged.
(Figure 6). Roller choppers are manufactured in several diameters and
lengths. For added weight the drums can be filled with water. Two
equi-sized choppers usually are pulled either in tandem (one behind
the other and offset at an angle) or in duplex (side by side). The
tandem configuration is used most commonly for saw-palmetto con-
Choppers should be pulled at 6 to 8 mph, which is fast enough to flip
the soil. When saw-palmetto are greater than 5 feet in height, chop-
pers should be pulled slowly the first time over the ground to prevent
excess wear and tear of equipment. It is recommended that a second
pass over the area be made at right angles to the first pass in all stands
of saw-palmettos in order to get maximum chopping action and flip of
the soil. This second pass should be made as soon after the first pass as
possible in order to reduce added stress on the forage species as they
begin to regrow.
The web plow is a 6-to-8-feet-wide, winged-shaped blade that is
sharpened on the leading edge. During operation the blade is inserted
into the ground to a depth of 4 to 6 inches. The plow severs subterra-
nean stems and roots of saw-palmetto but causes little soil distur-
bance. A web plow can be attached to a road grader or may be a
separate implement that is pulled behind a tractor with rubber tires. It
is important to obtain sufficient overlap of the blade, or strips of un-
treated saw-palmetto will remain. It is suggested that all pine stumps
be removed before web plow treatment to reduce wear and tear on
Saw-palmetto usually is burned the winter prior to mechanical
treatment application to reduce height shrub growth. This facilitates
Figure 5. Tandem roller chopper pulled by a crawler tractor.
Photo courtesy of USDA-Soil Conservation Service
treatment application and weakens the plant as hypothesized for her-
bicide treatment. Given that carbohydrate reserves fluctuate during
the year, season of mechanical treatment also may affect saw-
palmetto responses to mechanical treatment.
Table 3 summarizes several studies that have tested chopping or
web plowing at various seasons or soil moisture conditions. Saw-
palmetto responses to the mechanical treatments ranged from a 1% in-
crease in plant density to a 94% reduction. Lewis' (1972) data in-
dicated chopping killed over twice the amount of saw-palmetto than
webbing at 6 months post-treatment. However, this large disparity in
results was not statistically significant. Conversely, Tanner et al. (un-
published) results indicated that webbing gives somewhat better con-
trol than chopping in both wet and dry seasons, respectively, although
only a single pass of the choppers was tested in this study.
In general, data presented in Table 3 suggest that substantial reduc-
tion in saw-palmetto can be derived from both chopping and web
plowing throughout the year, with exception of the Tanner et al. April
(dry)-chop treatment. Given that stored carbohydrate levels are
lowest in late summer, especially following a prescribed winter burn
(Kalmbacher et al. 1983), the expectation is that saw-palmetto mortal-
ity should be increased if mechanically treated at this time. Saturated
soil conditions in late summer should place added stress on the plants.
Longevity of Treatments
Long-term studies of saw-palmetto control have not been con-
ducted. Most herbicide studies were established on smaller plots and
were not monitored once the researcher finished the original study.
Figure 6. Web plow mounted beneath a road grader.
Table 3. Summary of studies using roller chopping or web plowing to reduce saw-palmetto plant density
Month of Years Reduction
Authors Treatment Application Preburn Post-treatment (%)
Lewis (1970) Chop June Yes 5.0 73
Lewis (1972) Chop May Yes 0.5 92
Web May Yes 0.5 42
Moore (1974) Chop Jan. Yes 2.0 94
May Yes 2.0 70
Aug. Yes 2.0 94
Kalmbacher and Chop June _' 3.0 63
Martin (1984) Dec. -3.0 65
-2 Yes 3.0 58
No 3.0 45
Tanner et al. Chop3 April (dry) Yes 3.0 +1
(unpublished) Aug. (wet) Yes 3.0 67
Web April (dry) Yes 3.0 59
Aug. (wet) Yes 3.0 75
Average over burn and unburned pretreatment.
2 Average over June and December chopping dates.
3 Single chop-all other chop treatments were double chopped.
Mechanical treatments, however, have been used by ranchers for
many years on operational-size pastures as a common range improve-
ment practice. Although no quantitative data are available, ranch
records and personal observations of ranchers indicate that web plow-
ing will give a longer lasting control of saw-palmetto than chopping.
Tall, dense stands of saw-palmetto usually need to be rechopped
within four to five years (Mr. E. R. Felton, ALICO Corporation,
LaBelle, Fl). At the Agricultural Research Center, Ona, Fl., native
range areas that were web plowed in the mid to late 1960s are still
relatively free of saw-palmetto. Retreatment is recommended when
the saw-palmettos regrow to 30 inches in height and occupy approx-
imately 30 percent of the surface area on the ground.
Post-Treatment Grazing Guidelines
A major objective in controlling saw-palmetto is to increase her-
baceous forage production so that beef production on a per-acre basis
can be increased. Since saw-palmetto serves as protection for the
preferred forages, care must be taken not to overgraze the pasture
once the saw-palmetto has been controlled. It is recommended that
any site treated with chemicals or mechanical cultural practices not be
grazed until adequate forage is available. Overgrazing of pastures
receiving saw-palmetto control may result in the total loss of a seed
source for the better grasses. Areas treated in the spring or summer
may be grazed the following winter, but the forages should only be
grazed lightly. By the end of the following growing season, the pasture
can be stocked fully to use properly the available forage. It is recom-
mended that some type of rotational grazing system be used in order
to insure that the better forage species have an opportunity to
replenish above ground growth and carbohydrate reserves.
Range Management Costs
The cost of performing range management practices in Florida vary
considerably based on machinery, materials, methods, sites, sizes of
acreage, and operators. Regardless of the circumstances everyone
should develop an estimate of the per acre cost to perform range
management practices under their conditions. This cost estimate will
provide the basis for evaluating which practices will pay for
themselves on an individual's range setting.
Determining the cost of each range management practice often re-
quires the native range operator to sort out the finer details of what in-
puts were used to perform the range management practice and apply
a charge for each of those inputs. Basically, costs for these items may
be separated into operating costs (variable costs such as fuel, oil, and
labor) and ownership costs (fixed costs such as depreciation, in-
Table 4. Costs of performing range management practices
Cost Machinery/ Costs/Acre2 Duration Cost/Acre3
Management Practices' Level Material ($) (years) ($)
Burn low Tractor & Harrow 0.10 3 0.04
high Tractor & Harrow 0.20 3 0.08
Chop low Tractor & Tandem
Chopper 8.00 7 1.75
high Tractor & Tandem
Chopper 14.00 7 3.07
Web Plow low Tractor or Grader
Web Plow 12.00 15 1.76
low Tractor or Grader
Web Plow 18.00 15 2.64
1 Each management practice was evaluated using a low and high level of estimated cost per acre. The estimates are representative of the wide varia-
tion in cost per acre of performing range management practices based on various conditions of custom rates and self-performed with new and used
machinery and equipment. The estimated low and high level of cost per acre, however, do not represent the maximum or minimum cost per acre.
Given the appropriate circumstances (size of acreage, site condition, new or used machinery, etc.) lower or higher cost per acre may be realized.
2 Cost per acre includes the operating (fuel, oil, lubricants, labor and materials) and ownership costs (depreciation, insurance, repairs, taxes and
interest) per acre to perform the range management practices.
3Amortized cost per acre describes the annual per acre cost incurred if the total cost per acre of the range management practice was financed over
the effective time period of the practice (years) using a 12% annual interest rate.
surance, repairs, taxes, and interest on capital assets). These costs
must be converted to a per unit basis ($/acre, $/cow, etc.) in order to
determine the cost of the practice. The sum of operating and owner-
ship costs represents the total cost of performing the range manage-
Cost of tandem chopping and web plowing are evaluated using a
low and high level of estimated cost per acre, as shown in Table 4.
These estimates are representative of the wide variation in cost per
acre of performing range management practices based on various con-
ditions of custom rates and self-performed with new and used equip-
ment. The estimated low and high level of cost per acre, however,
does not represent the maximum to minimum cost per acre. Given the
appropriate circumstances (size of acreage, site condition, new or used
machinery, etc.) lower or higher cost per acre may be realized.
Total cost per acre was amortized to describe the annual per acre
cost incurred if the total cost per acre of the range management was
financed over the effective time period of the practice (years) using a
12 percent annual interest rate. The amortized cost per acre will per-
mit the range operator to evaluate costs and benefits of the manage-
ment practice and make a more informed decision.
1. At the present time, herbicide treatment can not be recom-
mended since the Environmental Protection Agency (EPA) has not
licensed any commercial use of the experimental chemicals at the
rates needed to kill adequately saw-palmetto.
2. Both roller chopping and web plowing provide substantial
canopy control. The time of mechanical treatment that appears to be
best is in late summer when the plants have their lowest levels of
stored carbohydrates, and when the soil is often saturated. Web plow-
ing is recommended above roller chopping because saw-palmetto
cover is reduced for much longer.
3. The cost of performing saw-palmetto control has to be recovered
in increased carrying capacity on the land. On-going research is at-
tempting to estimate the amount of increased forage production that
will be required to pay for range management practices. Since increas-
ing forage yield and quality is a major goal of saw-palmetto control,
post-treatment grazing must be managed properly to maintain and
enhance the grazing resource.
4. It is recommended that total treatment of large pastures not be
practiced. Saw-palmetto-dominated range in Florida provides cover
and food for many species of wildlife. Not only is saw-palmetto
browsed by cattle in winter, it is felt that the presence of saw-palmetto
is important in maintaining huntable populations of white-tailed deer
and bob white quail.
Burton, G. W., and R. H. Hughes. 1961. Effects of burning and 2,4,5-T
on gallberry and saw-palmetto. Journal of Forestry 59:479-500.
Hilmon, J. B. 1968. Autecology of saw palmetto (Serenoa repens
(Bartr.) Small). Ph.D. Dissertation, Duke University. 190 p.
Hough, W. A. 1968. Carbohydrate reserves of saw-palmetto: seasonal
variation and effects of burning. Forest Science 14:399-405.
Kalmbacher, R. S., K. J. Boote, and F. G. Martin. 1983. Burning and
2,4,5-T application on mortality and carbohydrate reserves in
saw-palmetto. Journal of Range Management. 36:9-12.
Kalmbacher, R. S. 1984. Light relationships between saw-palmetto
and creeping bluestem. Ona Agricultural Research Station Re-
search Report RC-83-2. Institute of Food and Agricultural Sci-
ences, University of Florida. pp. 20-25.
Kalmbacher, R. S., and F. G. Martin. 1984. Chopping and tebuthiuron
effects on saw-palmetto. Soil and Crop Science Society of Florida,
Lewis, C. E. 1970. Responses to chopping and rock phosphate on
south Florida ranges. Journal of Range Management. 23:276-282.
Lewis, C. E. 1972. Chopping and webbing control saw-palmetto in
south Florida. U.S.D.A. Forest Service Research Note SE-177,
Southeast Forest Experiment Station. Asheville, NC. 6p.
McCaleb, J. E., E. M. Hodges, and C. L. Dantzman. 1961. Effect of
herbicide control of saw-palmetto on associated native forage
plants in peninsular Florida. Journal of Range Management.
Moore, W. H. 1974. Some effects of chopping saw-palmetto-pineland
throughout range in south Florida. Journal of Range Manage-
Tanner, G. W., W. S. Terry, and R. S. Kalmbacher. Mechanical brush
control on south Florida range. Submitted to Journal of Range
Yarlett, L. L., and R. D. Roush. 1970. Creeping bluestem (Andropo-
gon stolonifer (Nash) Hitch). Journal of Range Management.