Australian pines are a cause of contention in River Bridge, a planned community  of 1,100 homes in the City of Greenacres in Palm Beach County. Some residents  want these trees removed; others defend them.  

 The River Bridge Property Owners Association in 2011 took a hands-off approach,  noting that a county requirement to remove existing Australian pines (also  called Casuarina trees) applies only within 500 feet of a designated natural  area.  

 The fuss over River Bridge’s Australian pines arose for several reasons. Their defenders like their stately  appearance and the dense shade they provide, but opponents note that they  spread aggressively; they have thick, shallow, broad roots that overrun lawns;  and they emit a chemical that discourages the growth of other plant species  nearby. Also, their brittle wood breaks easily. Entire trees are prone to  topple in high winds.  

 Australian pines also invade beaches, where their sprawling root system  discourages sea turtles and American crocodiles from nesting.  

 Crawling, Flying and Creeping

 Australian pines are not the only invasive species giving Floridians a major  headache. Giant snakes, snails and rats are threatening to upset the ecosystem  of the Sunshine State.  

 One species making its unintended home in Southern Florida is the Burmese  python. The snake, apparently introduced after exotic pet owners dumped them  into Everglades National Park, was first spotted there in 1979. Known to grow  up to 26 feet in length, these predators routinely snack on alligators, rodents  and other large animals and even have been found to have ingested a full-sized  deer.  

 Last year Everglades National Park spokeswoman Linda Friar said the snakes  (which may number upwards of 180,000) were so thoroughly adapted to the  Everglades that there is no hope of eradicating them. The best hope is to  prevent the pythons from spreading.  

 Since pythons are secretive in nature and remain inactive much of the time,  scientists have brought in bomb sniffing dogs to curb the snake population in  the Everglades. In one case the dogs helped researchers trap a pregnant snake  with 19 eggs. The Florida Fish & Wildlife Conservation Commission (FWC) issues permits to allow the capture of  the exotic reptiles from the Everglades. You can call the FWC’s Exotic Species Hotline at 888-IVE-GOT1 (888-483-4681) to report a Burmese  python.  

 In 2011, Florida’s Department of Agriculture and Consumer Services issued a warning about another  species bothering homeowners: the Giant African Land Snail. According to the  report, the slow-moving sloth can consume 500 different types of plants, can  cause structural damage to plaster and stucco and carries a parasite that can  lead to meningitis in humans. Originally from East Africa, the snail can grow  up to eight inches in length and more than four inches diameter. The snail’s life expectancy can stretch up to nine years and they are abundantly prolific.  Over 78,000 snails have been collected on 350 properties in 18 core areas of  Miami-Dade County. The Giant African Land Snail has not been found outside of  Miami-Dade County, according to the DACS.  

 Another invader is the native African Gambian pouched rat, larger than the size  of the average house cat. The rats have been rapidly reproducing in the Florida  Keys despite a ten-year effort to wipe them out. In 2009, the Florida Fish & Wildlife Conservation Commission thought the region was in the clear, but the  furry rodents—some weighing as much as an astounding nine pounds—came back with a vengeance.  

 The Gambian pouched rats can have a negative impact on local animal species and  crops and are expected to disrupt South Florida’s fragile ecosystem. They’ve also been linked to a 2003 outbreak of Monkeypox, a version of human  smallpox, in the Midwest.  

 According to the U.S. Department of Agriculture, the rats can reproduce quickly  and do so only five months after being born. They bear up to six babies at a  time and only have to wait nine months before bearing another litter. Officials  plan to use cantaloupe and peanut butter to lure the rats into traps in an  effort to clear the Keys of the invader.  

 Melaleuca and Brazilian Pepper

 In the plant arena, “Melaleuca is the ‘poster child’ of Florida’s invasive plants,” notes Jeffrey Eickwort, a biologist and supervisor in the Florida Forest  Service, an agency of the Florida Department of Agriculture and Consumer  Services. Introduced from Australia in the mid-1880s to dry out wetlands and  for ornamental use, it has spread across hundreds of thousands of acres where  nothing else now grows. Removing these Melaleuca monocultures will continue  indefinitely and has already cost millions of dollars.  

 Moreover, “Melaleuca flowers put out a volatile resin that causes all kinds of respiratory  problems in susceptible people. If your eyes swell up and you have to take  Claritin when these trees bloom, that’s the reason,” explains Roger Hammer, retired senior interpretive naturalist for the  Miami-Dade County Parks Department.  

 Brazilian pepper in its native habitat grows as a small beachfront shrub in a  varied plant community just above the high-tide mark. In Florida, where it was  introduced before 1891, it can grow to a height of 30 feet and choke out  everything else around it. Often called Florida holly due to its bright red  berries, Brazilian pepper is a member of the cashew family. It can cause  caustic burns on the skin of people allergic to the sap of other cashew cousins  such as mango and poison ivy.  

 “Brazilian pepper is a banned plant in Miami-Dade County but it still sprouts up  because birds spread the seeds, and because some people still like it,” says Dr. John McLaughlin, home gardening specialist in the Miami-Dade County  Cooperative Extension Service. “Legally, it can’t be sold and it can’t be planted, but if one volunteers on your property, then it grows. All we can  do is urge you to remove it.”  

 Vines, Grasses, and More

 Not all invasive plants are trees. Florida has nuisance vines and grasses, too,  and a number of aquatic plants.  

 The Old World climbing fern is a vine that can quickly smother all other  vegetation. “It was introduced by the nursery trade, according to records going back to 1958,” Eickwort says. “It reproduces with tiny spores rather than seeds, making it very easy to spread.”  

 The gold coast jasmine vine gives a tree on which it grows the illusion of a  thick canopy. “The vine is difficult to eradicate,” McLaughlin says. “You can’t get rid of it without damaging the tree. You have to cut the base of the vine  near the ground, put an appropriate herbicide on the cut, and wait until the  vine dies so you can see where it is.”  

 On the lawns of condominium and homeowners association communities, an  assortment of invasive grasses give lawn-maintenance contractors grief, says  Steve Swangin, an executive with Lukes-Sawgrass Landscape in Dania Beach, a  subsidiary of Continental Properties, Inc. In particular, he lists cogon grass,  nut grass, and torpedo grass—all Old World species. “You just live with them in your soil, or you dig them up and replace them,” he says. “If you go to kill them, you might as well redo your sod because nothing is left.  They choke out all the grass.”  

 Burma reed, an Asian grass that grows to a height of eight feet, is invading  South Florida’s endangered pine rocklands and imperiling adjoining condo and HOA communities. “When Burma reed gets entrenched in pineland, it becomes a monoculture—just pine trees and Burma reed,” Hammer says. “This changes the fire regimen dramatically, creating a huge fire load with  flames 30 feet high that can kill the pines.”  

 Hammer says residents of communities next door to a pineland react with  understandable apprehension when officials announce that a prescribed burn has  become necessary. “They go in with all their equipment on a day when the wind is calm and  everything is perfect so you won’t have a wildfire at 2 a.m. that will burn your house down,” he explains.  

 Perhaps the best-known aquatic invader, the water hyacinth, is a South American  native with pretty blue flowers. It was brought to the U.S. for the 1884  World's Industrial and Cotton Centennial Exposition in New Orleans. An  exposition attendee from Florida took several plants home and released them  into the St. Johns River, where they spread rapidly. Two plants can produce  1,200 daughter plants in four months, and a single plant can release up to  5,000 seeds, many of which are eaten and transported to new locations by  waterfowl.  

 Toxic Invasive Plants

 Some invasive plants should be removed from a residential community because they  can kill people and domestic animals.  

 The rosary pea vine, originally from India, has bright red and black seeds that  look like rosary beads and attract children. The seeds contain the poison  abrin. “If you chew one and swallow it, you will die from gastrointestinal hemorrhaging,” warns Hammer.  

 Castor bean seeds contain another poison, ricin, which has been studied as a  biological warfare agent. Eating these seeds also can cause death. The plant  comes from the eastern Mediterranean, Africa, and India.  

 Several invasive species of Lantana shrubs from the Greater Antilles exist in  Florida. “Lantana kills more grazing cattle in the world than any other plant,” Hammer says. “Eating the green unripened fruits will kill people. The ripe fruit is metallic  deep blue and is still toxic. Lantana also can give your dog a severe liver  disorder.”  

 The pothos vine contains fine calcium oxalate crystals that resemble microscopic  shards of glass. “It’s a tremendous skin irritant,” McLaughlin notes. A western Pacific Rim native, the pothos vine grows into  palms and other trees. “People sometimes purposefully plant it, and then it’s hard to get rid of,” he says. “It will sprout from stems. If you don’t pick up all the stems, they will take root and grow.”  

 Control Methods

 Control of invasive plants is a chore best left to the experts. Community  maintenance personnel who don’t know what they are doing may inadvertently spread the noxious plants they are  trying to eradicate, or accidentally poison residents and pets.  

 “We try to remove everything manually,” Swangin says, “although sometimes we use chemicals to remove Brazilian pepper and Melaleuca  roots. When we mow our lawns and trim, the crews hose down and clean their  equipment so they’re not moving material from one place to another.”  

 Hammer says the appropriate procedure for Burma reed involves using a weedeater  with metal blades to cut the plants down to the ground. “Then you bundle the cut stems and haul them off the property in a truck, wait a  month for the plants to resprout, and spray them with the herbicide Roundup,” he says.  

 When exotic plants arrive in Florida without their natural enemies, one way to  control them is to import some of those enemies from their native range. “Classical biological control involves finding an organism that feeds only on  that plant, and (after a long quarantine period to make sure it won’t harm our native species or crops) releasing it here. If it works, this can ‘tame’ an invasive plant, making it less of a problem in our environment,” explains Eickwort.  

 Examples of successful biological control agents include a moth that feeds  specifically on the Old World climbing fern, two successful insects for  Melaleuca, and two weevil species and a moth for water hyacinth.  

 Choosing the Right Plants

 Still another way to control invasive plants is to not plant them in the first  place. Especially in communities 30 or 40 years old, many plants originally  specified by landscape architects now are considered invasive. These include  acacias, Bischofia, carrotwood, Ficus nitida (Indian laurel fig), guava, Hong  Kong orchid tree, Java plum, Lantana, and pongam, Swangin says.  

 Hammer advocates native plantings—especially tropical trees bearing small fruits that birds eat. “If you landscape your property properly, it can be a critical stopover for  migratory birds moving through, and a haven for resident birds,” he explains. Also beneficial are native plants that attract adult butterflies  and their larvae.  

 Hammer advises condo and HOA associations to commit to such a strategy, and then  consult landscapers and nurseries that specialize in native plants. Additional  guidance is available through the Florida Native Plant Society, which has  chapters all over the state. Still another resource, Fairchild Tropical Botanic  Garden in Coral Gables, holds plant sales featuring native species, and bird  and butterfly days where experts help visitors learn to identify species at  Fairchild that also may be present in their own yards and neighborhoods.  

 McLaughlin cautions, however, that being a native shouldn’t be the only criterion for plant selection. “Always go by the adage, ‘The right plant in the right place,’” he emphasizes. “If it needs a lot of water, don’t plant it in full sun on bare limestone. If it likes shade, make sure it will  get some.”    

 George Leposky is a freelance writer and is a frequent contributor to The South  Florida Cooperator.