Invasive Non-Native Plants in Florida, Introduction

NON-NATIVE INVASIVE PLANTS
An Introduction

BACKGROUND INFORMATION

Pictured here: A water hyacinth infestation in Fisheating Creek, Florida. The plants are jammed up against a bridge in the far distance — a flood waiting to happen.
Unfortunately, almost every place on earth is being invaded by plants from other places. Our "coontail" plants are invading South Africa. Southeast Asia's hydrilla is invading the U.S. Our native and desirable tape grass is an unwanted invader of Australia's rivers. Old world torpedo grass is growing wildly across Florida, and we're finding it very difficult to manage.

Read on to find out more about some of the problems caused by invasive plants in Florida and what you can do to help.

There are thousands of species of plants in the United States, with more than 4,000 known to be in Florida. Most plants in Florida's wild areas are native terrestrial plants; they live on dry land. But Florida is also home to hundreds of native plants that live in damp to wet soils, and even underwater. Together, they total about 3000 native plant species. The Native Freshwater Plants photo-murals depict just a few of Florida's native freshwater wetland and aquatic plants.

If we “do the math,” we can see there are about 1,000 non-native plants found in Florida. While most are benign (not a problem), there are about 130 plant species that are proving to be quite invasive in our state natural areas and other lands; they’re spreading on their own and causing environmental and economic harm. About 30 plant species are causing serious damage and it’s costing millions of dollars to try and control or manage these plants.

You can help by learning more about Florida’s native, non-native and invasive plants and by helping us locate and control these silent invaders.

NATIVE Plants

Native plants have evolved within their own ecological niches, and are not invasive within their own native ranges. Native plants provide food and shelter to our animals of all sorts, stability to our shorelines and fields, and visual pleasure of the highest order. Because a native plant species usually does not take over its home range, there is biodiversity -- a number of species growing in balance and living together in harmony. Florida is famous for its biodiversity. Biodiversity exists when species are constrained in their growth by natural factors, so they can't overrun their neighboring species. Such natural growth restraints include:

competition with other native species,
diseases,
feeding by insects and other animals,
climate, and so on.

By definition, native plants are not invasive. However, sometimes, when a habitat or site becomes "disturbed," (i.e., from construction, digging, or when water level fluctuations have been altered by man-made drainage or pumping systems, or when excessive amounts of fertilizer enter the water body), then certain native plants have been known to cause problems. Our native cattails (Typha species) are famous for quickly filling in wet areas that have been disturbed or altered. They are often the dominant plant in man-made ponds and ditches. In the Everglades, for example, cattails are crowding out the desirable saw-grass (Cladium jamaicense), which produces food and shelter for native Everglades’ animals. It is believed that man-made alterations in water level fluctuations as well as nutrient input have given an advantage to cattail over saw-grass in certain areas. For the most part though, native plants are in balance with their environment.

NON-NATIVE Plants

Of the more than 4,000 plant species in Florida, perhaps 1,000 species or more (25%) are non-native; they’re also referred to as "exotic." We define non-native plants as "those that have become part of the Florida flora following the occupation by European man." In other words: plants that have made their way here since 1513 are considered non-native. (Source: Richard P. Wunderlin, © 2006 Institute for Systematic Botany)

The term non-native usually refers to plants from other countries, regions or continents; kariba weed (Salvinia molesta ) probably comes from Brazil, and Brazilian pepper (Schinus terebinthifolius) comes from South America, etc. However, the term can also apply to plants from another region (i.e., within the same country). An example: smooth cordgrass (Spartina alterniflora), a native desirable plant on the U.S. Atlantic coast is invasive on the Pacific coast, covering oyster beds and other vital habitat.

Not all non-native plants are problematic . A wide variety of agricultural plants, such as tomatoes, citrus trees and other "economic crops" in Florida are obviously "good" and essential to human health and our economy. These plants are well managed by the farmers who plant them and sell their valuable products. Rarely do our non-native food crops spread as weeds. (As far as we know, there aren’t any forests being threatened by tomato plants.)

Some ornamental non-native plants (roses,etc.) also are benign. Genetics, climate, soil, disease, insects prevent some cultivated plants from being able to spread on their own; they simply will not survive unless humans take care of them. As a result, they generally don’t cause any significant problems in the wild. Therefore, we have little to worry about when it comes to certain non-native plants that will not spread “on their own.”

INVASIVE Plants: What’s the problem?

Under the right conditions, some non-native plants can become invasive. An invasive plant is a non-native plant species that has escaped cultivation, is spreading on its own and causing environmental or economic harm.

Invasive non-native plants can outgrow, replace, and otherwise destroy our native plants. That's because non-native plants usually do not have their natural enemies -- the diseases, insects and other environmental stresses -- that keep them in check in their native ranges. The destruction and replacement of our native plants has several significant consequences:

Our natural biodiversity is destroyed;
Our native plants can be eliminated;
Our wildlife have evolved to use native plants are not able to make use of non-native plants. As a result, they

leave the area or die off;

invasive plants can completely fill the water column or cover the surface so that fish are driven from the area;
swimming, boating, hiking and other uses can be affected or even dangerous in areas with invasive plants.

For photographic depictions of some of the least desirable (invasive) plants now found in Florida and elsewhere see the Invasive Non-Native Plants murals (http://plants.ifas.ufl.edu/mural2.html) or our website, which features over 500 plant species ( http://plants.ifas.ufl.edu/plants&animals.html ).

HOW DO NON-NATIVE PLANTS GET HERE?

Non-native plants find there way here through a variety of ways; any of us could have accidentally introduced them:

as seed and plant contaminants in imported nursery plants and soils;
as misidentified/unknown plants sold to/by aquarium keepers, water gardeners, landscapers and friends;
as whole plants and growing fragments in ballast water in foreign ships coming to our ports;
on those fruits and flowers you brought home in your vacation luggage;
and as hitchhikers on boat trailers, props, dive gear, or in bait wells.

In the past, some species were purposefully introduced to "improve" our natural areas. For example, melaleuca trees (Melaleuca quinquenervia) were introduced to Florida from Australia by spreading their seeds from airplanes over the Everglades. At the time, land managers wanted the trees to suck up the “excess” water and make the Everglades more “suitable” for human use while providing a source of wood. The plan resulted in millions of invasive melaleuca trees covering half a million acres which are now known to be destructive to Florida's endangered Everglades environment and animals. Melaleuca trees now are being removed at a huge expense.

HOW DO PLANTS SPREAD?

Plants reproduce and spread by several means. All flowering plants produce seeds – some even grow flowers and are pollinated under water, like the naiads. Depending on the plant, its location and other circumstances, plants may spread when:

their seeds are dispersed by wind, water, or birds and other animals;
vegetative “propagules" fall off and form new plants;
the plant is somehow fragmented (such as by a boat propeller) and the plant parts re-grow into new plants;
yard waste is taken elsewhere;
the root system expands and gives rise to new plants.

MANAGING INVASIVE PLANTS

Undeniably, there are other non-native plants already introduced to Florida that someday will be invasive weeds. We don't want to continue to allow destructive species into the state. The question is, "How far on the side of safety should state regulatory agencies go in NOT permitting the importation, growing or selling of non-native plants?"

One of the most difficult things an eco-management agency can do is predict, before hand, which non-native plants might become terribly invasive on their own, and which non-native plants would be benign. That's why there sometimes are controversies between government agencies and plant growers or importers. A grower may say there is not enough evidence to show that a plant would be invasive while the governing agencies might feel there is a legitimate reason to prohibit a plant from entry into the state.

To that end, t he University of Florida/Institute of Food and Agricultural Sciences (IFAS) has developed a working group of scientists that provide consistent recommendations concerning the use of non-native plants in Florida. The Assessment and the Working Group were created in response to the growing awareness of the threat posed (especially to threatened and endangered species) by non-native invasive species. For more information: http://edis.ifas.ufl.edu/AG100 and http://plants.ifas.ufl.edu/assessment/ .

The Florida Exotic Pest Plant Council (FLEPPC) is a volunteer organization of plant management professionals who also assesses the threat of Florida's non-native plants and then categorizes them according to their invasiveness. It defines Category I plants as "invasive exotics that are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives." As of 2006, there are at least 125 non-native invasive plants that meet that criterion in Florida.

As is now well known, some nursery-sold and pet-store-sold plants are invasive or are believed by scientists to have the high potential to become invasive: plants such as certain bamboo and grass species, certain tree and vine species, certain aquatic species, and others.

One invasive plant, the Chinese tallow tree (Sapium sebiferum), a very pretty shade tree, is an example of an invasive tree that was sold widely before it was discovered to be taking over some of Florida's wetlands. For example, thousands of Chinese tallow trees have spread on their own is Paynes Prairie State Park near Gainesville; the trees are so plentiful that lots of money and labor is now required to destroy them.

Another invasive non-native plant is hydrilla (Hydrilla verticillata). It was introduced as an aquarium plant and sold in stores. Hydrilla grows very well, now infesting tens of thousands of acres in Florida public waters. It has also spread to nearly 20 states as far away as Massachusetts and California. Hydrilla requires constant management with chemicals and machines; management costs in Florida public waters for this single plant species approach $20 million every year.

Invasive non-native plants must be controlled; ignoring them is not an option . Because it's unlikely that an established non-native plant species can be eradicated from natural areas, we often have to settle for the goal of "maintenance control." This means using all appropriate tools to “control” or keep the plants at the lowest level possible while conserving or enhancing native plants.

There are several control methods used to achieve maintenance control, depending on the plant and its habitat:

Chemical control (http://plants.ifas.ufl.edu/guide/herbcons.html ) is the use of specially formulated herbicides (registered with the U.S. EPA and the Florida Department of Agriculture and Consumer Services) to kill plants.

Biological control (http://plants.ifas.ufl.edu/guide/biocons.html) is the use of imported insects, fish and other organisms which eat or infect or otherwise keep the invasive plants at low levels indefinitely. Before releasing such organisms, the USDA and the Florida Department of Agriculture and Consumer Services must verify that insect biocontrols have proven to be host-specific.

Mechanical control (http://plants.ifas.ufl.edu/guide/mechcons.html) is the use of specially-made machines to "harvest" invasive plants by cutting and collecting them and transporting them to a place to decompose.

Physical control includes using hands, drawdowns (water removal), flooding, burning, dredging and shading to control invasive plants. Integrated control is the use of two or more of the above methods.

STEWARDSHIP: WHAT CAN WE DO?

When buying plants, choose a legitimate nursery, and confirm that the vendor is aware of what species are restricted, both regionally and federally. Be sure to verify the correct plant identification and common names. For aquatic plants, rinse them in a bucket of tap water to remove unwanted sediments and/or bugs.

When disposing of plants that have the potential of spreading into nearby woods or waterbodies, completely dry or freeze the plants to kill them, and then add them to household garbage that will NOT be composted. Incineration is another possible alternative.

Learn how to identify invasive non-native plants, as well as our native plants. It's not so difficult to learn a few plants that are interesting or important to you.

INVASIVE PLANTS IN FLORIDA
Among Florida's invasive plants are trees, shrubs, vines, grasses, and ferns (with 100 ft. leaves!). And there are even some of those aquarium plants and flowering plants we've purchased at the garden store. And through the catalogs. And over the Internet.

INVASIVE NON-NATIVE AQUATIC AND WETLAND PLANTS

wetland nightshade
Solanum tampicense East Indian hygrophila
Hygrophila polysperma giant salvinia
Salvinia molesta hydrilla
Hydrilla verticillata para grass
Urochloa mutica torpedo grass
Panicum repens

water hyacinth
Eichhornia crassipes water lettuce
Pistia stratiotes water spinach
Ipomoea aquatica West Indian marsh grass
Hymenachne amplexicaulis wild taro
Colocasia esculenta

We don't know which is worse - hydrilla or water hyacinth. Arguably, water hyacinth was the original "invasive aquatic plant" of the U.S.; more than 100 years ago the federal government began the battle to control it. Thus evolved the first practical experiences in the art and science of invasive plant management. While water hyacinths used to make rivers and lakes impassable in the U.S., the plant is now under "maintenance control", so newcomers rarely see it as a problem. On the other hand, the submersed plant, hydrilla, is not yet under maintenance control, so it frequently is the subject of conversation among boaters, fishermen, and swimmers in Florida. Millions of dollars are spent every year on its management. Other aquatic/wetland invasive non-native plants include wild taro which can grow in the water and out of it. (Wild taro looks similar to elephant ear, another non-native plant.) Torpedo grass has claimed hundreds of thousands of acres from our native favorite, maidencane. Alligator weed is an invasive plant that can be claimed as a "biological control success", having been placed under maintenance control mostly by three introduced insect species including the alligator weed flea beetle. Various species of hygrophila (including East Indian hygrophila), are favorite aquarium plants and also invade our waters. And then there's paragrass, West Indian marshgrass, water spinach, water lettuce, giant salvinia (under "invasive ferns", above) and aquatic night shade. Information and photos of all these and other invading aquatic and wetland plants may be found here.

INVASIVE NON-NATIVE TREES

Chinese tallow
Sapium sebiferum melaleuca
Melaleuca quinquenervia Brazilian pepper-tree
Schinus terebinthifolius Australian pine
Casuarina equisetifolia Chinaberry
Melia azedarach mimosa tree
Albizia julibrissin

WHEN TREES COLLIDE!
Seven species in one Miami
scenic; none native.

Invasive trees! It may seem unlikely that non-native trees could invade and infest large areas. After all, we notice quickly when trees are growing in places where we don't want them, and isn't it easy enough simply to yank the seedlings out of the ground, or chop down the one big tree? But what if we weren't paying attention for years? What if even our favorite store-bought tree turned out to be one of the worst invaders? What if we see the invaders, but they are on highway rights-of-way, and, hey, we have stuff to do - let the highway people notice them and do something. Or what if the trees were spreading in places that we don't usually go, or can't even get to, such as the middle of the Everglades?

In Florida, there are many invading trees, some like Chinese tallow and melaleuca that thrive in the shallow littoral waters of lakes and rivers. Chinese tallow, which we freely spread ourselves - just a few years ago, we gave them as Christmas presents, they're so pretty and shady. Then the birds found the tallow berries and seeds, and now this tree infests thousands of acres of Florida's wildest forests. And also the wild forests of Louisiana, Texas and South Carolina. There's also the melaleuca tree which seed was spread from airplanes, on purpose, so as to dry up the Everglades. Now we know better and want them out of there, and it's costing millions of dollars a year in manpower and helicopter-applied herbicides. There's the Brazilian pepper, the tree which has spread the most through Florida, and which might be called the worst of the tree invaders in our state. Thousands of square miles of forests, wetlands, farmlands, pastures and highway rights-of-way are blighted with dense stands of Brazilian pepper. And the Australian pine, a tree which was also planted on purpose, but whose virtues have been shown to be modest, while it spreads as far north as winter's frost will allow. Chinaberry is a tree in northern Florida, lovingly planted by our great grandparents, but now spreading on its own. There's the mimosa tree, with its puffy pink flowers and large sun-filtering leaves - it's an invader too. Not to mention earleaf acacia, orchid tree, camphor tree, carrotwood, laurel fig, guavas, Java plum, seaside mahoe... Information and photos of all these and other invading trees may be found here.

INVASIVE NON-NATIVE SHRUBS

nandina
Nandina domestica Chinese ligustrum
Ligustrum sinense Surinam cherry
Eugenia uniflora shoebutton ardisia
Ardisia elliptica coral ardisia
Ardisia crenata lantana
Lantana camara

Florida has even more invasive shrubs than it has invasive trees. And many of our invasive shrubs were also plants we purchased and planted. Among them are nandina and Chinese ligustrum, two favorite easy-to-grow items planted by homebuilders and "landscapers". And there's Surinam cherry with the colorful fruit - it's making its way into Florida forests. Two shrubs of the Ardisia genus are rapidly spreading - one in southern Florida, the other in northern Florida. Shoebutton ardisia is a very robustshrub that looks very much like its native cousin. Coral ardisia is another of those store-bought escapees. Lantana is another increasingly common invasive plant, as are half-flower, downy rose myrtle, and day jessamine. Information and photos of all these and other invading shrubs may be found here.

INVASIVE NON-NATIVE VINES


kudzu Pueraria montana	air potato Dioscorea bulbifera	Chinese wisteria Wisteria sinensis	cat's-claw vine Macfadyena unguis-cati	skunk vine Paederia foetida	rosary pea Abrus precatorius

Another Florida floral feature is its vines. Among our native vines are about a dozen smilax vines and a dozen wild grape species, cross vine, coral honeysuckle, Dutchman's pipe, peppervine, Virginia creeper, poison ivy, Florida air potato, yellow jessamine, trumpet creeper, coral beads, moonseed, who knows how many morning glory vines, and the lovely American wisteria (not to be confused with Chinese wisteria).

Add to these the invasive non-native vines: There's the house-covering kudzu, a plant that was purposely planted around the south. Two kinds of non-native air potatoes (to outcompete our native air potato) - also purposely introduced. Another is Chinese wisteria, a much more robust (and invasive) plant than our native American wisteria. Cat's-claw vine is an up-and-comer which already has a fair hold in northern Florida. We can't forget two stinking invasive vines that smell like their names (olfactomatopoeia): skunk vine and sewer vine. Skunk vine is well established in forests and waste places from southern to northern Florida. Rosary pea is another; a well-masticated seed can kill (i.e. is poisonous). Florida's invasive vines also include Japanese honeysuckle, latherleaf, gold coast jasmine, Brazilian jasmine, arrowhead vine, and two very troublesome vine-ferns (see "invasive ferns" below). Information and photos of all these and other invading vines may be found here.

INVASIVE NON-NATIVE FERNS

Old World climbing fern
Lygodium microphyllum Japanese climbing fern
Lygodium japonicum Boston fern, sword fern
Nephrolepis cordifolia Incised halberd fern
Tectaria incisa giant salvinia
Salvinia molesta water fern
Salvinia minima

Ah, the ferns of Florida. As befits a subtropical paradise, we have many attractive native ferns - too many to recount here. And they are also being threatened - by non-native ferns. The two worst fern invaders actually look like vines. The Old World climbing fern is smothering trees in the southern part of the state. (Their fronds can be 100 feet long!) And the Japanese climbing fern is becoming more of a nuisance in the northern part of the state. Another fern invading our forests we've purchased at the stores: Boston fern. (It looks so much like one of our native ferns, who knew?) Another fern, incised halberd fern is directly competing with our native halberd fern in southern Florida. The non-native ferns are also invading our waterways: the floating fern giant salvinia is a newcomer that we're very worried about, and water fern is so common now that most people think it's a native. FYI - the non-native "asparagus fern" is not a fern. Information and photos of all these and other invading ferns may be found here.

INVASIVE NON-NATIVE GRASSES

cogon grass
Imperata cylindrica Burma reed, silk reed
Neyraudia reynaudiana elephant grass
Pennisetum purpureum giant reed
Arundo donax Johnson grass
Sorghum halepense West Indian marsh grass
Hymenachne amplexicaulis

One would think Florida had enough grasses. But not everyone thought so, and introduced about a dozen new grasses anyway, and now those are "on the list", the invasive plant list that is. Our native grasses are quite diverse: the plume grasses, muhly grasses, cockspur grasses, love grasses. But now they're being supplemented with cogon grass, a plant which knows no boundaries. And there's burma reed; once for sale as an ornamental, it can now be obtained free from just about any spare lot in Dade County. Though we have no elephants, we do have elephant grass, which commonly grows 12 feet tall. Giant reed is another ornamental escapee, and is well-disliked in California as well. Johnson grass has been with us for a while and is quite common in north Florida. Among other places, the Myakka River is infested with the non-native invasive West Indian marsh grass. And there's Vasey grass, guinea grass, natal grass, paragrass, fountain grass, smut grass, and quite a number of bamboos - all invasive, non-native grasses in Florida. Information and photos of all these and other invading grasses may be found here.

The Creators

This page was authored by Vic Ramey.
Data is from the APIRS database.
Photography and graphics are by Ann Murray, Sara Reinhart and Vic Ramey.
This page is maintained by Alison Moss.

For DEP, this page was reviewed by Jeff Schardt and Judy Ludlow.

Main Index

This project is a collaboration of
the Center for Aquatic and Invasive Plants, University of Florida,
and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection


wetland nightshade Solanum tampicense	East Indian hygrophila Hygrophila polysperma	giant salvinia Salvinia molesta	hydrilla Hydrilla verticillata	para grass Urochloa mutica	torpedo grass Panicum repens


water hyacinth Eichhornia crassipes	water lettuce Pistia stratiotes	water spinach Ipomoea aquatica	West Indian marsh grass Hymenachne amplexicaulis	wild taro Colocasia esculenta


Chinese tallow Sapium sebiferum	melaleuca Melaleuca quinquenervia	Brazilian pepper-tree Schinus terebinthifolius	Australian pine Casuarina equisetifolia	Chinaberry Melia azedarach	mimosa tree Albizia julibrissin


nandina Nandina domestica	Chinese ligustrum Ligustrum sinense	Surinam cherry Eugenia uniflora	shoebutton ardisia Ardisia elliptica	coral ardisia Ardisia crenata	lantana Lantana camara


Old World climbing fern Lygodium microphyllum	Japanese climbing fern Lygodium japonicum	Boston fern, sword fern Nephrolepis cordifolia	Incised halberd fern Tectaria incisa	giant salvinia Salvinia molesta	water fern Salvinia minima


cogon grass Imperata cylindrica	Burma reed, silk reed Neyraudia reynaudiana	elephant grass Pennisetum purpureum	giant reed Arundo donax	Johnson grass Sorghum halepense	West Indian marsh grass Hymenachne amplexicaulis

NON-NATIVE INVASIVE PLANTS An Introduction

BACKGROUND INFORMATION

NON-NATIVE INVASIVE PLANTS
An Introduction