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Invasive Fern Capable Of Toppling Florida Tree

Leon County Judge John Cooper on June 30, 2022, in a screen grab from The Florida Channel.
Amy Green
The Florida Channel
LeRoy Rodgers of the South Florida Water Management District is surrounded by Old World Climbing Fern on a tree island in the Everglades.

LeRoy Rodgers pulls a pair of clippers from a bag and hops off an airboat. He’ll need the clippers to cut a path through the Old World Climbing Fern choking this island of trees within the Arthur R. Marshall Loxahatchee National Wildlife Refuge, part of the Everglades.

“A white-tailed deer trying to make your way through this,” he says. “You can see how difficult it would be.”

The florescent green fern renders the tree island virtually impenetrable. It cascades from wax myrtle and dahoon holly trees, its dead vermicelli-like vines weaving a thick brown mat near the ground obstructing every step. Without help the trees will collapse beneath the stranglehold.

Rodgers of the South Florida Water Management District says the islands dotting the sawgrass prairie here are where birds and other wildlife forage and nest. He takes the fern in his hand.

“See the little inundations here? Those little toothlike features? That’s where the spores are produced. Now that you know what you’re looking for if you look out you can see they’re everywhere. So there are spores by the billions all around us right now, and that’s the other part that makes this plant so invasive.”

The Old World Climbing Fern is Florida’s latest and greatest invasive plant species.

The fern is native to Africa, Asia and Australia and first appeared in Florida as an ornamental plant. With no natural predators here it grew unchecked.

“I think it is the worst invasive species that Florida has faced in a very long time.”

Cheryl Millett of The Nature Conservancy considers herself on the front line of the fern’s northward march. She is part of a team of government agencies and private land owners monitoring its spread in central Florida. She steps among the pine trees of an 8-acre conservation area in a residential neighborhood of Oveido. The fern flows from trees like a waterfall.

“We’ve had really wet and mild winters, and so you see it growing right now. It’s not cold enough for it to die back. So it’s actually got more time to grow. It will spore practically year-round.”

Crews control the fern by spraying it with herbicide and hacking at it with machetes, leaving the vines overhead to die. Millett says it’s exhausting work beneath the Florida sun.

“They’ve got their big boots on. They’re coming through, and before they treated all of this, this was all covered up here. And so they have to hack through all of that, cut it with machetes, climb through. You saw the blackberries growing in here, the thorny vines they have to go through. It’s really hard work.”

Back in Loxahatchee, Rodgers motors over to another tree island. On this one the Old World Climbing Fern only is beginning to grow.

“Here you can actually make out individual trees in the canopy, first of all. You can see that there’s at least 40 trees here, probably about five different species of trees. And in some areas you can actually see a little bit of an understory, shrubs and ferns.”

Rodgers says biologists also are experimenting with a moth and mite found where the fern originates and that feed only on the plant.

“These tree islands are something that took centuries and millennia in some cases to form, and so it’s worth the battle to win.”

In the Everglades the fern stands to take down more than tree islands. Its grip on Loxahatchee has prompted the state to threaten to terminate its lease authorizing the U.S. Fish and Wildlife Service to manage the land.

Such an action would mean the end of the refuge and is strenuously opposed by environmental groups in a region where a multi-billion-dollar environmental restoration is underway.