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Two vegetative forms are recognized. The common type is
yellow-green in color, while the less common type is a blue-green color
sometimes referred to as the silver form (Essig et al. 2000). This type occurs
in a continuous stretch in a narrow belt along Florida’s east coast from St.
John’s to Dade Counties, and occasionally inland in Polk and
Highlands Counties (Essig et al. 2000).
S. repens is easily recognized by its multiple
leaves, or fronds, that protrude from horizontal stems the occur at or slightly
below ground level. Fronds are evergreen and palmate (fan-shaped), measuring
approximately 1 m (3 feet) in width. Petioles bear sharp spines from which this
species earned its common name. Flowers are white and borne on stalked panicles
growing from leaf axils. Fruit is a yellowish green in the unripe state,
gradually turning blue-black as it ripens. Fruits are fleshy and ellipsoid in
shape.
II. HABITAT AND DISTRIBUTION
Regional Occurrence:
Serenoa repens, saw palmetto, is endemic to
coastal plains from South Carolina to southeastern Louisiana including the
Florida peninsula.
IRL Distribution:
Saw palmetto occurs in every county of Florida.
It is common throughout the Indian River Lagoon area in both scrub and upland
communities.
III. LIFE HISTORY
AND POPULATION BIOLOGY
Age, Size, Lifespan:
Maximum growth of established trees occurs during the summer rainy season, when up to 80% of annual production is accomplished from April through October (Olson
and Barnes 1974). Estimates of stem growth range from 0.04 inches per year in
Georgia to approximately 0.1 inch per year in Florida (Tanner et al. 1996). By
using these estimates, Tanner et al. (1996) reported that some plants could be
as old as 500 – 700 years.
Three to seven leaves are produced each year, and these may remain on the
tree for as long as 2 years. Palmate leaves may measure 1 m (3 feet) in width
(Tanner et al. 1996).
Serenoa repens attains a height of 0.6 – 2.1 m (2 – 7 feet) as a shrub, 6
– 7.5 m (20 – 25 feet) as a small tree. Its height is dependent upon the
habitat it is grown in, with shrubs more common in scrublands, and trees more
common in maritime hammocks and uplands.
Abundance:
Saw palmetto is one of the more common shrubs in the scrub areas bordering
the Indian River Lagoon. It is also highly abundant as an upland tree.
Locomotion:
Sessile.
Reproduction:
Saw palmetto grows vegetatively from horizontal stems and rhizomes. Sexual
reproduction occurs via seeds. Flowers of Serenoa repens are pollinated by
insects, and bloom from April through July (Hilmon 1969; Olson and Barnes 1974).
Fruits ripen from September through October and are dispersed by animals (Olson
and Barnes 1974).
Seedlings grow slowly, with plants becoming fully established after 3-6
years. Saturated soils that occur throughout the summer rainy season retard
early growth. Flooding is a major preventative of establishment (Hilmon 1969).
Embryology:
Germination may take as long as 6 months, as the fruit endocarp and seed coat
must first deteriorate due to its impermeability to oxygen (Hilmon 1969). In
laboratory studies, Hilmon (1969) found germination rates of approximately 55%;
but field planting of seeds produced much lower rates of only 19.5%. It has been
suggested that seed germination is enhanced by being passed through animal
digestive tracts (Tanner et al 1996).
IV. PHYSICAL
TOLERANCES
Temperature:
Average annual temperature within the range of S. repens is from –4 to
36 ° C (25 – 97 ° F)
(Wade and Langdon 1990).
Salinity:
While this species is common on scrublands and in maritime forests, it may be
somewhat sensitive to salt spray (Bennett and Hicklin 1998).
Physical Tolerances:
S. repens is especially resistant to fire even though its foliage is
highly flammable. It is a frequent invader to sites defoliated by previous fires
(Abrahamson 1984b), and is classified as a survivor species due to its ability to
resprout from rootcrowns and rhizomes following a fire. Leaf production
following fire is initiated by using carbohydrates stored in rhizomes to increase
stem density and production. Its fire response is so strong, that even if burned
during the winter dormant season, S. repens will produce leaves and fruit
out of season. S. repens recovers from fire very quickly, with cover
returning to pre-burn levels within a year (Hilmon 1969; Abrahamson 1984a).
V. COMMUNITY
ECOLOGY
Trophic Mode:
Autotrophic.
Competitors:
Serenoa repens seedlings are susceptible to competition from other scrub and
upland plants (Hilmon 1969).
Habitats:
S. repens is a characteristic component of pine flatwoods, prairies,
scrub, and live oak-sea oats communities. It is a prominent indicator of in
poorly drained soils in pine flatwoods (Tanner et al. 1996).
It generally grows best in dry, well-drained soils rather than in swampy
areas (Monk 1965; Abrahamson 1984b). Typical soils are high in quartz and
fine-grained, but this species is also known to grow on poorly drained sites
high in peat (Breininger and Schmalzer 1990).
Saw palmetto grows best in warm-temperate, or humid-subtropical climates.
Average rainfall within its range is approximately 100 – 163 cm (39 – 64
inches) per year, and average temperatures range from -4 to 36°
C (25 – 97 ° F) (Wade and Langdon 1990). This
species grows well in either shade or in sun (Duncan and Duncan 1988), and is a
common member of fire-climax communities (Wade et al. 1980; Taylor, and Herndon
1981).
It is a common understory shrub in coastal strands and in oak-pine
communities. In scrub communities, saw palmetto provides habitat for sand
skinks, the Florida mouse, and the threatened Florida scrub jay (Austin 1976).
Its fruit provides food for black bear and white-tailed deer. In upland
communities such as palmetto prairies, saw palmetto is primary habitat for
burrowing owls, caracaras and sandhill cranes (Callahan et al. 1990).
Associated Species:
Plants associated with saw palmetto commonly include overstory varieties
such as slash pine (Pinus elliottii), pond pine (P. serotina),
longleaf pine (P. palustris), sand pine (P. clausa) and cabbage
palm (Sabal palmetto). Understory associates include live oak (Quercus
virginiana), myrtle oak (Q. myrtlifolia), pawpaw (Asiminia
reticulata), scrub mint (Conradina grandiflora) and gallberry (Ilex
glabra) (Monk 1965; Austin 1976; Wade and Langdon 1990).
Florida wood rats, wild turkey and white-tailed deer are all known to use
palmetto as cover or for nesting (Tanner et al. 1996). In addition to black bear
and white-tailed deer, feral pigs,
raccoons, foxes, deer, and gopher tortoises all utilize saw palmetto fruit
for food. Black bear and feral pigs also eat apical meristems (heart) of the
plant (Bennett and Hicklin 1998).
VI. SPECIAL STATUS
Special Status:
None
Benefit in IRL:
S. repens is an ecologically important species that provides nesting,
protective cover and an important food source to other species of birds and
mammals (Tanner et al. 1996).
At archaeological sites throughout central Florida, saw palmetto, sea grape (Cocoloba
uvifera), and cocoplum (Chrysobalanus icaco) are all ubiquitous
(Bennett and Hicklin 1998). Saw palmetto appears to have been one of the most
important food sources for Florida’s pre-Columbian population, for the later
Miccosukee and Seminole tribes, and for subsequent settlers such as the Spanish
during the sixteenth century. Even as late as the early 1900s, pioneers used saw
palmetto berries to make soft drinks (Bennett and Hicklin 1998).
The medical value of S. repens has been reported since the 1800s (Hale
1898 in Tanner et al. 1996). Bennett and Hicklin (1998) reported over 50
medicinal uses of saw palmetto extracts for illnesses ranging from whooping
cough to alcoholism.
Economic Importance:
S. repens has previously been used to produce pulp for paper products,
but it is considered to be of poorer quality compared with other tropical
species (Olson and Barnes 1974).
Of significant importance is a drug called Serenoa, marketed as
Permixon®, which is extracted from partially ripened, dried fruits of saw
palmetto. This drug has been successfully used to treat, prostrate swelling,
bladder infections and urinary tract infections. In prostate disorders,
extracted Serenoa repens compounds inhibit the enzymes responsible for conversion of the
male hormone testosterone to DHT, dihydrotestosterone, a
hormone that binds to receptor sites on prostate
cells, and adversely affects gene transcription and the regulation of biological
responses in these cells (Plosker and Brogden
1996). In urinary tract disorders, treatment of men with S. repens
compounds helped reduce urinary frequency, increase urinary flow, and improve
symptoms of dysuria (painful urination).
VII. REFERENCES
Abrahamson, W.G. 1984a. Post-fire recovery of Florida Lake Wales Ridge
vegetation. American Journal of Botany 71(1):9-21.
Abrahamson, W.G. 1984b. Species response to fire on the Florida Lake Wales
Ridge. American Journal of Botany 71(1):35-43
Austin, D.F. 1976. Florida scrub. Florida Naturalist. 49(4):2-5
Bennett, B.C. and J.R. Hicklin. 1998. Uses of saw palmetto (Serenoa repens,
Arecaceae) in Florida. Economic Botany 52(4):381-393.
Breininger, D.R. and P.A. Schmalzer. 1990. Effects of fire and disturbance on
plants and birds in Florida oak/palmetto scrub community. American Midland
Naturalist. 123(1):64-74.
Callahan, J.L., C. Barnett, J.W. Cates. 1990. Palmetto prairie creation on
phosphate-mined lands in central Florida. Restoration and Management Notes.
8(2):92-95.
Essig, F.B., Y.R. Taylor, and D. TeStrake. 2000. Florida’s wax palm: the
silver
form of Serenoa repens (Arecaceae). Florida Scientist
63(1):13-16.
Gholz, H.L., D.N. Guerin, and W.P. Cropper. 1999. Phenology and productivity
of saw palmetto (Serenoa repens) in a north Florida slash pine
plantation.
Canadian Journal of Forestry Research 29:1248-1253.
Hilmon, J.B. 1969. Autecology of saw palmetto (Serenoa repens (Bartr.)
Small).
Dissertation Abstracts.
Monk, C.D. 1965. Southern mixed hardwood forest of north central Florida.
Ecological Monographs. 35:335-354.
Olson, D.F. Jr., and R.L. Barnes. 1974. Serenoa repens (Bartr.)
Small
saw-palmetto. In: Schopmeyer, C.S., ed. Seeds of woody plants in the
United
States. Agric. Handb. 450. U.S. Department of Agriculture, Forest
Service.
Washington, D.C. 769-770.
Plosker, G.L. and R.N. Brogden. 1996. Serenoa repens (Permixon
®): a review
of its pharmacology and therapeutic efficacy in benign prostatic
hyperplasia.
Drugs and Aging. 9(5):379-395.
Tanner, G.W., J.J. Mullahey and D. Maehr. 1996. Saw palmetto: an ecologically
and economically important native palm. Wildlife Ecology and Conservation
Department, Florida Cooperative Extension Service, Institute of Food and
Agricultural Sciences, University of Florida. Circular WEC-109.
Taylor, D.L., and A. Herndon. 1981. Impact of 22 years of fire on understory
hardwood shrubs in slash pine communities within Everglades National Park.
Report T-640. National Park Service, South Florida Research Center,
Everglades
National Park, Homestead, FL. 30 pp.
Wade, D.D., J. Ewell, and R. Hofstetter. 1980. Fire in south Florida
ecosystems.
Gen. Tech. Rep. SE-17. U.S. Department of Agriculture, Forest
Service,
Southeastern Forest Experiment Station. Asheville, NC. 125 pp.
Wade, D.D., and O.G. Langdon. 1990. Sabal palmetto (Walt.) Lodd. ex.
In:
Burns, R.M., and B.H. Honkala, technical coordinators. Silvics of North
America. Vol. 2 Hardwoods. Agric. Handb. 654. U.S. Department of
Agriculture,
Forest Service. Washington, D.C. pp. 762-767.
Report by: K. Hill, Smithsonian Marine Station
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