Field biologist treks through tropical hardwood hammocks to collect rare fern spores
Somewhere in the southern reaches of Miami-Dade County, the only fern of its kind known to grow wild in the continental U.S. survives under a thicket of Brazilian pepper.
Botanists have long worried that the fern — discovered in 2006 near Florida City in a location they prefer not to disclose — could be just one hurricane, plant poacher or misfired shot of herbicide away from disappearing forever. So two years ago a team led by Fairchild Tropical Botanic Garden launched a rescue mission, ultimately more drudging than gripping, to collect and propagate spores no bigger than the period at the end of this sentence.
Then they waited.
“I had a heck of a time getting spores,” Fairchild botanist Jennifer Possley said this month when she displayed the fruits of the mission: a wispy, Caribbean maiden hair fern, about six inches tall and one of about 20 now growing at the garden.
Despite the success, the maiden hair could be the poster plant for a fern crisis playing out across Miami-Dade.
With 124 natives ferns, Florida has more species than anywhere else in the U.S. outside Hawaii or Puerto Rico, Possley said. Of those, 48, grow in Miami-Dade County. More than half, 26, are imperiled or in danger of going extinct. Fourteen have already disappeared.
If the surviving ferns grew in large, protected preserves like Everglades National Park or the Big Cypress National Preserve, Possley said she would worry less. But seven are found only in a patchwork of small preserves managed by Miami-Dade’s Environmentally Endangered Lands program — the last fragments of hardwood hammocks and pine rockland now surrounded by highways, commercial districts and busy neighborhoods.
“This is where I come in and start to sweat,” Possley said.
Native ferns, before the introduction of invasive ornamentals like sword fern, were once ubiquitous in South Florida, inspiring an avid following among admirers who flocked to fairy-like grottoes, braving thorny vines and spiders, in search of rare species. Tours were led into fern-lined sinkholes.
“Fern enthusiasts like me consider it a small price to pay,” Possley wrote for an article about conservation efforts.
But, like dozens of other rare plants and creatures, wild ferns began fading from the landscape. Heavy development has shrunk habitat. Poaching by collectors nearly wiped out some species.
With their slow incubation, ferns aren’t built for fast rebounds. One plant can produce billions of spores — Possley says they’re “everywhere on earth,” floating through the air — but ferns can be picky about where they grow.
Consider the brown-hair comb fern. First spotted at the Deering Estate in 1962, the rare fern was nearly wiped out about three years ago when the South Florida Water Management District began restoring historic water flow to Biscayne Bay as part of Everglades restoration work. Alerted to the threat because she tracks rare plants for the county, Possley and other Fairchild botanists collected spores just before the population crashed.
Then began the arduous work of growing the ferns. Mike Freedman, Fairchild’s horticulturist, spent months tending to the spores, constructing a special plexiglass chamber to improve their chances of surviving. Six weeks after germination, the ferns remained tiny, revealing heart-shaped leaves only under a microscope. At three months, they measure about an inch-tall, looking a little like parsley. At about a year, the ferns are finally two to three inches tall and large enough to be potted and shipped to a greenhouse where Possley and other botanists have been growing about 300 plants representing a dozen rare species.
Within a year of another endangered fern — the grid-scale maiden fern — dying at the Deering Estate, Fairchild was able to reintroduce a new crop of greenhouse ferns to repopulate the area. The brownhair fern managed to hold on, Possley said.
Beyond poaching and loss of habitat, another threat increasingly puts ferns at risk: rising sea levels linked to climate change that could alter the specific habitat some ferns require. Fairchild is now working to identify county land where rare ferns would have grown historically so they can be replanted. The garden is also sending seeds to the nation’s seed bank, the National Center for Genetic Resources Preservation in Colorado where seeds and animal tissue important to U.S. agriculture are stored.
Possley would love to see the “little fairy gardens” that once drew tourists replanted. But she recognizes the challenges.
“Now most of them are buried underneath Miami,” she said.