National Park Mystery Plant 1: Will This “Lime-Green Cancer” Derail Everglades Restoration?
This is the inaugural posting in our new National Park Mystery Plant series. We hope to eventually make the mystery plant quiz a regular feature of Traveler.
This virulently invasive plant, sometimes called the “lime-green cancer,” is arguably the most dangerous plant in Florida. It already infests Everglades National Park, and if it isn’t controlled it might obliterate decades of ecosystem restoration efforts. Do you know what this nightmare plant is?
It’s native to wet or moist subtropical habitats in Africa, Southeast Asia, and Australia, but it’s been in southern Florida for many decades and has been infesting areas of the Everglades since at least 1965. By 2003, the infestation reached at least 150,000 acres in total extent. Some areas of Everglades National Park are already infected.
The NPS is very concerned about the implications for the park. And no wonder! People who know what this exotic plant is and what it can do to the ecosystems it invades can’t help but feel a sense of dread.
You have to give the darn thing credit for being amazingly adaptable. Blown by the wind, its spores can infect new areas up to 40 miles away. It’s not real choosy, either. It can grow in sawgrass prairies, marshes, piney woods, hardwood hammocks, cypress sloughs, tree islands, mangrove swamps, roadside ditches, and a variety of other habitats.
Once established, it grows rapidly and lives for a long time. Unfortunately, this rapidly spreading menace not only extends horizontally, but also climbs into the uppermost branches of trees, sometimes reaching as high as 90 feet. Spreading laterally in the canopy, it covers the underlying branches and leaves with a dense mat that can be up to three feet thick in places.
The effect on native vegetation can be positively devastating. Plant diversity plummets in seriously infected areas as the understory vegetation is overwhelmed and whole stands of trees are smothered. Even rare plants are not spared by this relentless aggressor.
One of the more dangerous impacts of this nasty plant is the heightened risk of fire damage to trees. Ground fires that might otherwise yield generally beneficially results can end up being extremely destructive crown fires because the invader provides a “ladder” for the fire to reach into the canopy. Once there, the blanketing mat provides fuel as well as burning masses that may be spread by the wind to start new fires.
Even bald cypress trees growing in standing water can be placed at risk in this way. Whereas ground fires stop at the edge of cypress sloughs, being unable to advance because of the soggy ground or open water, crown fires can sweep through cypress trees infected with the lime-green menace and severely damage or kill them.
Controlling this dangerous invader is anything but easy. Once the plants are established, you can’t get the upper hand by simply severing the fronds wrapping around tree trunks and extending into the canopy. The plant will simply regrow if you do that, and you will get the same result if you try hand-pulling or burning. You can kill the plant with herbicides (assuming that’s feasible), but you still have to get rid of the dead material -- a time-consuming and expensive task – while taking great care not to release vast quantities of spores that can spread the infection. Leaving the dead material in place is not a good option, since the mat inhibits the growth of understory vegetation, starves trees of sunlight, supplies fuel for fires, and provides a means for fire to reach into the canopy.
Unless something is done soon (a self-sustaining biological control?) this nightmarish invader could cancel out efforts to restore the Everglades ecosystem to some reasonable semblance of health. Scientists are especially worried that the invader may have a ruinous effect on the native plants and animals inhabiting the vulnerable hardwood hammocks and tree islands.
Nearby Big Cypress National Preserve is infected as well.
Can you name this dangerous plant pest?
Answer: It’s the Old World climbing fern (Lygodium microphyllum), which is sometimes called (in addition to simply Lygodium) the snake fern, the small-leaved climbing fern, or the climbing maidenhair. See the Bugwood Network website for detailed information about the OWCF. An integrated management plan for the OWCF devised by the Florida Exotic Pest Plant Council Lygodium Task Force (2nd edition, 2006) can be viewed at this site.