The Common Staghorn Fern, Platycerium bifurcatum, Naturalizes in Southern Florida

4 Pages·2003·2.1 MB·English

by  Robert W Pemberton

American
Fern Journal 93(4):203-206
(2003)
Shorter Notes
Common
The
Staghorn Platycerium
Fern,
bifurcation, Naturalizes
— in
Southern
Florida. Platycerium
bifurcation (Cav.) C. Chr. a popular
is
ornamental
staghorn fern that is widely cultivated in the tropics and
and under New
subtropics
protection in cooler climates. Native
to Australia,
Guinea and
Indonesia (Jones, D. L. 1987. Encyclopedia of Ferns. Timber Press,
Portland, Oregon.), thrives out-of-doors southern where
in Florida,
it large
suspended by hung
cultivated plants chains from
residential trees or houses
are a frequent sight. These ferns are exceptionally abundant in some areas. For
instance, at least 19 large cultivated P. bifurcatum plants grow in 7 of the 11
yards on one street in Ft. Lauderdale, Broward County, southeastern Florida.
young
Early in 2001, sporophytes of a staghorn were observed growing on
[Quercus
virginiana Mill
January one
2002, of
the*
identified as P. bifurcatum
bif
trees across the street, within 50 meters of the colonized About one
half
tree.
mile away, two
P. bifurcatum plants "volunteered" on a live oak growing next
many
to a yard with large spore-producing bifurcatum These
P. plants.
colonizations appear be phenomenon
to a local related to the close proximity
of
fertile plants.
Later in January 2002, found P. bifurcatum growing in a native live oak
I
forest at Tree Tops County Park in southwestern Broward County. During
hour
a three survey
of the park, a total of 19 plants were located on 11 large live
oaks. Three plants had and two were clumps
fertile leaves, of these large of
more
plants than one meter across with numerous and and
basal foliage fronds,
remaining
16 sporophytes were of various sizes but all had at least one foliage
more
Most
m
larger branches 4.5 to 9 off the ground. These 11 host trees were scattered
within
a forest stand about 600 meters in length. Tree Tops Park
is
km
approximately 11 west of the Ft. Lauderdale residential oaks with the
colonizing bifurcatum
P. plants.
In January 2002, also surveyed the mixed hardwood forest the Broward
I at
County Flamingo Environmentally Sensitive Lands about eight km. west
Site,
A
of Tree Tops Park. single medium-sized plant of bifurcatum with multiple
P.
basal and foliage fronds was found during the two-hour search of the No
site.
fertile leaves were apparent on this plant, which was growing in a live oak
about meters above the ground.
five
An
unpublished list of the plants at Tree Tops Park and the adjacent Pine
Island Ridge Preserve, compiled by P. Howell in 1995, included bifurcatum
P.
Howell The was young
(P. pers. com.). plant a single sporophyte found
VOLUME NUMBER
AMERICAN FERN JOURNAL:
204 93 4 (2003)
growing on an oak the forest in 1994 Howell, pers. com.), which suggests
(P.
that the fern was naturalizing in the park by that date.
may
The age of the colonizing staghorn plants be judged by their size. Under
optimal conditions, can take bifurcatum up a year grow from a spore
P. to to
it
young and 3-4
to a sporophyte to initiate foliage fronds, another years to
produce fronds Hoshizaki, com.) Multiple basal fronds can be
fertile (BJ. pers.
produced after about two years. This suggests that 3 of the 19 plants at Tree
Tops Park are about a year old, 5 are 2 years or older, 8 are between 2 and 5
years old, and three are probably more than 5 years old. Because the growing
conditions in Broward County are probably suboptimal due to cool and dry
winter weather, the plants are probably older than they appear.
Both Tree Tops Park and the Flamingo Preserve have residential areas within
km
one of the park which could be spore sources. The source of spores the
for
Ft. Lauderdale residential oak colonization likely nearby cultivated plants
is
known
that occur within 100 meters of the not whether Platycerium
tree. It is
gametophytes The
are able to self fertilize (B. Hoshizaki, pers.com.). ability to
J.
would make
self fertilize naturalization easier because only one spore would
be needed and seems
to establish a plant population. Self fertilization
desirable in epiphytic ferns growing on tall trees in dense forests. Ferns that
more
are long distance dispersers are likely to self fertilize (Peck, C. Peck
}.,
and D. Farrar. 1990. Amer. Bot 80:126-126.). The two climbing ferns invasive
J.
in Florida, Lygodium japonicum (Thunb. ex Murray) Sw. and microphyllum
L.
can M. W. Pemberton and
(Cav.) R. Br., self fertilize (Lott, C. Volin, R.
S.,
J.
Amer.
D. F. Austin. 2003. Bot. 90:1144-1152.).
J.
In Australia, P. bifurcatum occurs in tropical and subtropical Queensland,
New
and
extends into temperate South Wales (Jones, D. L. 1987. Encyclopedia
Timber The
of Ferns. Press, Portland, Oregon.). fern has survived -9°C on
m
New
Mount
Boss in South Wales and occurs 240-450 near Sydney
at
it
th
(Graf, A. B. 1992. Tropica, Color Cylopedia of Exotic Plants, 4 Edition. Roehrs
New
Sydney
Co., East Rutherford, located about 34 degrees
Jersey.). is ca.
A
south latitude, whereas Broward County, Florida lies at ca. 26 degrees north.
commercial nursery of P. bifurcatum in West Palm Beach County, just north of
Broward many
County, has survived freezing temperatures during 40
years
its
of operation (D. Rowett, pers. com.). The nearby weather station
at
Loxahatchee recorded low temperature between -3 and -4°C
for eight years
between 1961 and 1990
(Southeast Regional Climate Center, 2002. sercc®
may
cirrus. dnr.state.sc.us). Older staghorn plants be able
to tolerate freezes
because rhizomes by
their are insulated the masses of base fronds and
new
sometimes have
the ability to produce base and foliage fronds the old
if
ones are killed. Florida's dry season can kill young plants, but larger plants are
resistant to drought (Dave Rowett, pers. com.). These factors suggest that
plants, should persist in southern Florida and based on low-temperate
bifurcatum should
tolerance, P. be able to extend distribution northward.
it
become
bifurcatum plants very dense on
If P. trees, they could displace
native epiphytes. In the oak forests presently colonized, most
of the branches,
including those with P. bifurcatum are covered with
resurrection fern
SHORTER NOTES
205
Humb. &
[Pleopeltis polypodioides Bonpl. ex Willd.), and five species of
&
bromeliads
[Tillandsia balbisiana Schult. Schult.f., fasiculata Sw.,
T. T.
T
recurvata setaceae Sw., usneoides
(L.) L., T. (L.) L., T. utriculata L.) are
Two
common.
and
of these bromeliads, T. fasciulata T. utriculata, are
endangered by
classified as the State of Florida because of the attack of an
which
exotic weevil specifically feeds on bromeliads (Coile, N.C. 2000. Notes
on endangered and
Florida's threatened plants. Florida Division of Plant
Bureau Entomology, Nematology and
Industry, of Plant Pathology-Botany
Section Contribution No. 38, 3rd edition, 122.). P. bifurcatum becomes
p. If
abundant in other preserves, which are rich in rare endangered epiphytic
orchids and bromeliads, could become more serious threat. presence in
it Its
Tree Tops and Flamingo represents another exotic species in natural areas
already plagued with abundant introduced species. a more obviously non-
is
It
component
native of the forests, than are the exotic figs [Ficus spp.) and
shoebutton ardisia [Ardisia elliptica Thunb.), which have native counterparts.
Given an
the incipient naturalization, despite apparent long history of
and modest abundance, seems
cultivation, unlikely bifurcatum
its that P.
it
approach Examples
will the severity of other invasive ferns in Florida. of
such include Lygodium microphyllum W. and
(Pemberton,
(Cav.) R. Br. R.
A. Ferriter. 1998. Amer. Fern 88:165-175.), japonicum (Thunb.) Sw.,
L.
J.
Nephroplepis
cordifolia (L.) C. Presl., N. multiflora (Roxb.) F.M. Jarrett exC.V.
Morton, and
Tectaria incisa Cav.. All of these are Category invasive exotics
1
(Austin et aL, http://www.fleppc.org/99list.htm).
Platycerium bifurcatum has probably had a long history of cultivation in
The
southern 1887 Palm
Florida. sales catalogue of the Royal Nursery, Oneca,
Manatee may
Co., lists P. alcicorne (Willem.) Tardieu. This species have
been
actually P. bifurcatum, a similar species (Hoshizaki, B. and R. C. Moran.
J.
2001. Fern Grower's Manuel. Timber Press, Portland, OR.). Platycerium
bifurcatum tolerates Florida's subtropical climate better than P. alcicorne,
native of eastern Africa and Madagascar (Hoshizaki and Moran, While
2001).
may
The
P. bifurcatum have naturalized previously, did not persist. plant's
it
many warm
horticultural forms (Hoshizaki and Moran, 2001,) and tropical to
temperate distribution (Jones, 1987,) suggests considerable genetic variation.
With and
increased population residential gardening, likely that there are
is
it
many may
more genotypes of P. bifurcatum plants present today and this
account for the current naturalization. Platycerium bifurcatum has naturalized
in Hawaii, where was documented occur on three islands in 1991 (Wilson,
to
it
K. A. 1996. Pacific 50:127-141.).
Sci.
number
With
the naturalization of P. bifurcatum in Florida, the of exotic
now
and Guide
ferns fern allies in the state 34 (Wunderlin, R. P. 1998. to the
is
Wunder-
Vascular Plants Florida. University Press of Florida, Gainesville).
of
which minima
32 species introduced, Salvinia Baker can be
lin as to
lists
added because of the recent recognition of the plant's exotic status (Jacono, C.
C, T. D. Davern and T. D. Center. 2001. Castanea 66:214-226.). These 34
same
represent about one-third of Florida's fern species, the proportion of
naturalized seed plants in the state. Thus there seems to be no difference in the
—
AMERICAN FERN VOLUME NUMBER
206 JOURNAL:
93 4 (2003)
and
ability of ferns seed plants to naturalize in Florida. In Hawaii, however,
where 19%
about half of the flora comprised of naturalized species, only of
is
the ferns are naturalized (Wilson, K. A. 1996. Pacific Sci. 50:127-141; 2002.
Amer. Fern
92:179-183), suggesting that ferns are less likely than seed plants
J.
on
to naturalize those islands. Both the proportion of ferns that are naturalized
and the severity of associated problems are greater in Florida than in Hawaii.
Barbara Joe Hoshizaki, Patricia Howell, Broward County Florida Parks and
Recreation, Dave Rowett Just Stags Nursery, Palm Beach Co. Florida, provided
New
helpful information. Robbin Moran, The York Botanical Garden, and
Barbara Joe Hoshizaki kindly reviewed and improved the manuscript. Robert
W.
Pemberton, Invasive Plant Research Laboratory, USDA-Agricultural Re-
search Service, 3205 College Ave., Lauderdale, FL 33314
Ft.