A Companion Resource for CAIP’s Photo Mural Set (UF/IFAS Publication # SP 336)
These ordered TEACHING POINTS were devised to help
school science teachers
and management agency trainers put together classes and lessons
about invasive plants.
They are particularly effective when used with the classroom-size invasive plant photo-murals.
Unfortunately, almost every place on earth is being invaded by plants from other places. Our coontail is invading South Africa. Sri Lanka’s salvinia is invading the U.S. Our native and desirable tapegrass is an unwanted invader of Australia’s rivers. Burma’s reed is growing wildly in south Florida, and we’re finding it very difficult to manage. Many of these non-native plants are invasive. “Invasive” here means “a non-native plant that has escaped cultivation and is spreading into natural wildlands and waters.” As of 2002, there are at least 100 invasive plants in Florida. (The Invasive Non-Native Plants mural depicts some of the least desirable plants now found in Florida and elsewhere.)
There are thousands of species of plants in the United States, with more than 4,000 species known to be in Florida. Most plants in Florida are native. They have evolved into their own ecological niches, and they are not invasive.
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 an area, 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:
Most plants in Florida’s wild areas are native terrestrial plants. Florida is also home to hundreds of native plants that live in damp to wet soils, and even underwater. (the Native Freshwater Plants photomural depicts just a few of Florida’s native freshwater wetland and aquatic plants.)
Of the more than 4,000 species in Florida, perhaps 1,000 species (25%) or more are non-native (exotic) plant species. We define “non-native plants” as, in Wunderlin’s words, “those that have become part of the Florida flora following the occupation by European man,” plants that have made their way to Florida since 1513.
“Non-native” usually refers to plants from other countries. For example, kariba weed (Salvinia molesta) probably comes from Sri Lanka, and Brazilian pepper (Schinus terebinthifolius) comes from South America, and so on. (See list of photo mural plants.) However, “non-native” might also simply refer to another region of a country. For example, the saltwater plant, smooth cordgrass (Spartina alterniflora), which is native and desirable on the U.S. Atlantic coast, is invasive -- covering oyster beds -- when it grows as a non-native on the Pacific coast.
What’s the problem? Invasive non-native plants can outgrow, replace, and otherwises destroy our native plants. That’s because non-native plants usually do not have their natural insect 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:
There is a difference between “non-native” and “invasive.” Non-native plants are “plants from someplace else”; non-natives are always “exotic.” However, some non-natives are also “invasive,” “nuisances,” “pests,” or “noxious,” meaning that they negatively affect our native plants and animals or hinder human use of our waters and lands.
How do non-native plants get here? In all sorts of ways. Any of us could have accidently introduced non-native plants:
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:
In the past, some species were purposefully spread in order 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. The idea was that the trees would soak up the water and make the Everglades better for human use. The plan resulted in millions of invasive melaleuca trees which are now known to be destructive to Florida’s environment and animals. Melaleuca trees now are being removed at huge expense.
Some non-native 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. No forests are threatened by tomato plants.
Some other non-native plants sold to the public also are benign, not easily spreading on their own, causing no significant problems in the wild; plants such as rosesand others which are planted for ornamental purposes in yards, parks and gardens. Usually these benign non-native plants will not grow if left on their own. For many reasons -- genetics, climate, soil, diseases, insects -- some cultivated non-native plants simply will not survive unless humans take care of them. Therefore, we have little to worry about when it comes to certain non-native plants that will not spread on their own.
Among other duties, state regulatory agencies must decide which plants it will allow to be distributed in the state. One of the most difficult things an eco-management agency can do is predict beforehand which non-native plants might become 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 that there is reason not to allow a plant into the state.
Undeniably, there are some 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 agencies go in not permitting the importation, growing or selling of non-native plants?”
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. One place where thousands of Chinese tallow trees have spread on their own is Paynes Prairie near Gainesville, where tallow trees are so plentiful that much money and labor is required to destroy them.
Another invasive non-native plant is hydrilla (Hydrilla verticillata), which was introduced as an aquarium plant and sold in stores. Hydrilla grows very well, now infesting hundreds of thousands of acres in Florida alone. (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 for this single species of plant are about $20 million every year.
By definition, native plants are not invasive. However, sometimes, when a site becomes “disturbed,” such as when construction has taken place, a ditch dug, or when water level fluctuations have been altered by man-made drainage or pumping systems, or when much fertilizer enters the water body, then certain native plants will act invasively. Our native cat-tails (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, cat-tails are crowding out the desirable saw-grass (Cladium jamaicense), which produces much 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 cat-tail over saw-grass in certain areas.
Invasive non-native plants must be controlled. Because it’s very unlikely that an established non-native plant species can be eradicated from wild areas, we must settle for the goal of “maintenance control.” This means we must use all available tools to control the plants at the lowest possible level.
There are several control methods that might be used to achieve maintenance control, depending on the plant and its habitat. Chemical control is the use of specially formulated herbicides (registered with the U.S. EPA) to kill plants. Biological control is the use of imported insects, fish and other organisms which eat or infect or otherwise keep the invasive plants at low levels indefinitely. Mechanical control 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.
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 to spread into nearby woods or waterbodies, completely dry or freeze the plants to kill them, and add them to household garbage that will not be composted. Incineration is a 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.
Plant common names are not very meaningful since they often are different from region to region, and often are changed by personal and marketing whim. For example, Nuphar advena is commonly known as spatterdock, cow lily, pads, flags and bonnets. So try to know plant scientific names.
What is a species and what is a genus? Taxonomy is the scientific classification of organisms. Plant and animal taxonomy is arranged in a hierarchy, from phylum down to species.
Phylum or division
A species is a population of one kind that does not successfully interbreed with populations of other kinds. A genus is a group of closely related species. In scientific names, the first word is the genus name and the second word denotes the species. Thus, in the example Eleocharis baldwinii, Eleocharis is the genus name, and baldwinii is the species name. The term Eleocharis sp. refers to any of the 150 species in the Eleocharis genus.
UF/IFAS CAIP Photo-murals (SP 336)
These Teaching Points were created to accompany a set of large format, laminated native, non-native and invasive plant photo-murals. We provide these free to any individual K-12 teachers in Florida who make a request in writing, on school letterhead. For more information: http://plants.ifas.ufl.edu/education
A USEFUL WEB SITE ~ http://plants.ifas.ufl.edu This web site was created and is maintained by those who brought you the plant photo-murals and this collection of Teaching Points. This web site includes pictures and descriptions of more than 500 species of native and non-native plants. Click on Plant Info & Images... This web site also includes plant drawings, online books, management manuals, freshwater scenics and other relevant materials.
A collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Invasive Plant Management Section of the Florida Fish and Wildlife Conservation Commission.
