All About Wetlands >> Vegetation
>> Exotic Vegetation
What is an exotic plant?
An exotic plant is a plant that has been introduced to an area outside
its native range. Often, when people come to visit or settle in Florida,
they purposefully bring seeds of their favorite plants with them
from other places. Other times, exotic species are transported accidentally,
where seeds or pieces of a vegetatively reproducing plant are unknowingly
attached to cars, boats, or even hiking boot shoes. Many of these exotic
species thrive Florida's subtropical climate, with warm weather, infrequent
freezes, and plentiful rain. Over time, if the introduced species cultivate
and grow wild in Florida, they are considered to be naturalized species.
Are all exotic plants a problem?
Not all exotic species cause a problem. In fact, most naturalized species
live in Florida without causing significant damage. However, some exotic
species do not have natural competition in Florida. As a result, they
grow rapidly, taking over natural vegetation and disrupting the habitat
and food sources for native wildlife. Florida spends millions of dollars
combating invasive vegetation each year.
Florida's invasive exotic wetland plants
The following wetland pest plants are included on the Florida
Exotic Pest Plant Council's (FEPPC) 2003 List of Invasive Species.
Click on the common name for more information and pictures of each species
from the University of Florida's Center
for Aquatic and Invasive Plants.
(Note: information on each species was summarized from
the Langeland/Burks book, Identification & Biology of Non-Native
Plants in Florida's Natural Areas)
Since the early 1900s, these evergreen trees have been planted extensively
across south Florida coastal dunes as windbreak and shade trees.
Australian pines are salt tolerant and can grow in the front-line
dunes, displacing native plants with rapid growth, dense shade,
and dense litter accumulation. They produce a chemical that inhibits
growth of nearby native plants. They reproduce prolifically, with
as many as 300,000 seeds per pound, and spread rapidly, with seeds
dispersed by birds, water and wind.
Similar to Casuarina equisetifolia, this tree was planted across
southern Florida coasts as a windbreak, roadside tree and hedge.
It suckers aggressively from spreading roots, creating dense jungle
of branches that excludes other vegetation. It tends to completely
take over areas where it becomes establish. This false pine colonizes
nutrient-poor soils easily by nitrogen fixing microbial associations.
This perennial herb was introduced to Florida in 1910 by the U.S.
Department of Agriculture as a crop substitute for potatoes. Today,
the crop is widely naturalized along streams, marshy shores, canals
and ditches, and has been found in 235 public water bodies.
Believed to have been brought to Jamaica in the 1850s from East
Asia for use as a medicine, food, fish poison and soap substitute,
this evergreen shrub became naturalized in the Florida Keys and
Everglades by the 1930s. It takes over native vegetation by entangling
stems several feet deep, growing over and shading out even trees.
It grows in many disturbed and undisturbed sites, including Florida's
coastal hammocks and the Keys, where it threatens a number of rare,
listed native plant species. Stems of the shrub can grow up to 32
feet in a single year. The plant forms adventitious roots where
branches touch the ground, and it vigorously resprouts from cut
or injured stems. Seeds are buoyant and salt-tolerant, making long-distance
This floating aquatic herb occupied 126,000 acres of Florida land
by 1950. It grows at explosive rates exceeding any other tested
vascular plant and can double its population in as little as 8 to
16 days. It creates dense mats on the water's surface, degrading
water quality and dramatically altering native plant and animal
communities. It reproduces both vegetative, from stem tips underneath
water surface, and sexually.
In 1994, this submersed, usually rooted, aquatic perennial herb
invaded more than 40 percent of Florida's water bodies. It creates
dense stands that alter fish populations, cause shifts in zooplankton
communities and affects water chemistry. The herb can produce up
to 6,000 tubers and 3,000 turions per m2, aiding its rapid dispersal
This perennial aquatic herb is replacing hydrilla as the most series
weed in south Florida canals. It grows rapidly, with the ability
to expand its population 100-fold in one year. Easily developing
new stands from rooted nodes of even small fragments, its spread
is difficult to control. It forms dense monoculture stands with
stem tips submersed up to 10 feet deep and can photosynthesize in
lower light than most native submersed species. Grows most vigorously
in flowing water.
Indian marsh grass
This dominant perennial grass species is replacing maidencane marshes
in the Myakka River basin, at Ringling MacArthur tract in Sarasota
County, Mountain Lake in Hernando County, and Fisheating Creek,
near Lake Okeechobee. It easily adapts to fluctuating water levels,
and can persist after long periods of drought or up to 40 weeks
of flooding. It produces seeds prolifically.
Scattered over the Everglades in the 1930s to create forests and
dry up the swampland, this grows extremely fast, producing dense
stand s that displace native vegetation and reduce native wildlife
habitat and food. In 1994, it infested an estimated 490,000 acres
in south Florida, especially Loxahatchee Slough, Big Cypress Swamp
and the Everglades. While regional control efforts have reduced
its coverage, it is recognized by the United Nations as a threat
to the Everglades. It produces up to 20 million windborne seeds
per tree per year and can hold the seeds for massive, all at once
releases in stressed conditions. Also, Melaleuca releases oils in
the air, especially in blooming season that may cause respiratory
irritation, asthma attacks, headaches or rashes.
This robust reed-like perennial is colonizes marginal and undisturbed
habitats. It is well established in the rock pineland habitats of
Dade County, where it is viewed as a threat to rare native species.
It is highly flammable and has been linked to fires outside Everglades
Introduced by the U.S. Department of Agriculture before 1897 as
a fiber crop, this perennial twining vine has invaded tree gaps
and disturbed areas across Florida. It creates dense canopies leading
to damage or death of native vegetation, adapting quickly to changes
in light, soil and salt conditions. This vine has is destroyed the
few remaining paths of the endangered Cooley's water willow.
This sturdy perennial grass is considered one of the most serious
grass weeds. In addition to infesting citrus groves and golf courses
across the state, it was found in 70% of Florida's waters by 1992,
displacing 14,000 acres of native marsh. It rapidly reproduces by
rhizome extension and fragmentation and is stimulated by tilling
and fertilization of soil. Each year, Florida spends an estimated
$2 million a year for to manage the weed in flood control systems.
This perennial grass has been reported as a weed in 29 Florida counties
and in 24 other countries around the world. It grows in dense reed
patches, preventing regeneration of native species. It can dominate
fire-adapted savanna communities and is often found in scrub, pine
rockland, hammocks, sinks, lake shores, swamps and prairie habitats.
In the past, this grass has created flood control problems by blocking
runoff's access to canals, reducing water flows and overgrowing
pump stations. Mechanical control is not an effective removal for
this weed, because it can easily resprout from leftover rhizomes.
Forming extensive mats this floating herb disrupts submersed plant
and animal communities, and interferes with water flow and navigation.
This plant may have been brought by humans as early as 1565 and
occurred in 128 state water bodies by 1989. Today, statewide management
programs have reduced the plant's abundance by half. Still the plant
is considered highly invasive, producing up to 1,000 rosettes per
m2 in South Florida. Water lettuce also serves as a host for at
least 2 genera of mosquitoes.
This deciduous tree grows up to 52ft tall, and is used in the U.S.
as an ornamental tree and potential oil crop species. It has expended
its range along the Gulf Coast in low-lying areas, becoming dominant
and spreading along roadside ditches to wet soil areas. It also
tends to take over large areas in well-drained areas near human
habitation in undisturbed areas like closed canopy forests, bottomland
hardwood forests, waterbody shores and even floating islands.
In 1997, this evergreen shrub or small tree is estimated have invaded
700,000 acres in central and south Florida. It forms tangled thickets
of woody stems, shading out and displacing native vegetation in
fallow farmland, pineland, hardwood hammocks, roadsides and mangroves
forests habitats. The tree produces allelopathic chemicals in the
soil which suppress the growth of other plants. It also produces
chemicals in leaves, flowers and fruits that irritate human skin
and respiratory passages.
Forming large, tangled, single-species stands, this sprawling prickly
shurb was prefers undisturbed wetland sites, typically invaded cypress
swamps and river margins. It can clamber over native vegetation,
dominate the understory of cypress heads, and grow over and cover
even large plants. It reproduces successfully, forming adventitious
roots at leaf axils and producing seeds that are viable for at least
12 months, showing 90% germination on fresh seeds.
This evergreen shrubby tree spreads its lower branches to create
impenetrable thickets and large fruit crops. It is commonly found
on coastal areas of south Florida and the Keys, especially in mangrove
communities and low-wave action beaches where its growth is adapted
to the salt spray and high winds. The tree thrives in low silty
land and coral and sand berms, and can shift into a more efficient
photosynthesis process (C4-type) under high saline conditions.
or white-flowered wandering Jew
This creeping branches perennial herb commonly forms dense single-species
ground covers that smoother native species. These herb blankets
can be up to 2 feet deep in overlapping leafy stems. The wandering
Jew is most commonly found in moist to wet hammock areas, well-drained
woodlands and shady residential yards. Though the plant is commonly
cultivated as a house or patio plant it is difficult to control
Considered one of the world's worst weed and reported as an agricultural
pest in 34 countries, this perennial grass forms from widely creeping
stolons. It's high productivity, fast growth and allelopathic abilities
(the grass releaseschemicals into the soil to kill nearby plants)
make it an aggressive plant creating single-species stands. Today,
it invades disturbed low areas like canals, and displaces native
vegetation along river and lake shoreline and in marshes and swamps.
In 1986 it was found in 52% of Florida's water bodies, but today's
coverage has dropped.
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