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Old World Climbing Fern
A federally listed invasive fern that climbs 100 feet into the canopy, blankets whole tree islands, and carries ground fire into the treetops. It is illegal to move or possess in Florida. This entry is for identifying and controlling it.
Not a food and not poisonous, but a genuine fire hazard: its mats form an unbroken fuel ladder from the ground into the treetops, and burning fronds lift on the wind to start spot fires ahead of the flame front. It spreads by clouds of near-invisible spores, so avoid cutting fertile fronds in dry, windy weather and clean tools, boots, and clothing afterward. Confirm the species before treating any climbing fern - the native Hartford fern is rare and protected.
Overview
The one thing to knowOld World climbing fern (Lygodium microphyllum) is the most damaging invasive plant in south Florida’s wetlands, and one of the strangest: a fern that climbs like a vine.
Old World climbing fern (Lygodium microphyllum) is the most damaging invasive plant in south Florida’s wetlands, and one of the strangest: a fern that climbs like a vine. A single frond never stops growing at the tip, so the wiry stalk twines up trunks and shrubs 90 to 100 feet, branching as it goes, until the whole canopy is roofed in a lacy blanket. Underneath, the mat smothers everything - and its weight collapses and topples mature trees. On Everglades tree islands and in cypress domes it has converted diverse habitat into a single fern.
Two things make it worse than an ordinary weed. It builds a continuous fire ladder: a ground fire that would have burned harmlessly through the understory climbs the fern into the crowns instead, and burning fern fragments lift on the wind and start spot fires well ahead of the flame front. And it spreads by dust-fine spores that travel for miles, so it appears in places nothing carried it. It is a federal noxious weed and on the Florida Noxious Weed List - illegal to introduce, possess, move, or release. You are here to identify it and get rid of it. Never plant it, and never move plant material out of an infested site.
Quick facts
For identification. Not a growing guide.
- Life cycle
- Perennial, lives about 20 years
- Where it grows
- Full sun · Part sun · Part shade · Shade, tolerates wet soil soil
- Height
- 30 ft5 to 100
- Spread
- 20 ft3 to 100
- Cold
- Killed by frostdamaged below 28°F
- Heat
- Struggles above 105°F
- Self-sows
- Yes. Never let it set seed.
Through the year
How to recognize it in each season.
Climbing fronds & smothering mats (identify & control)
year-round, every year- Recognize it: a fern that climbs, with small oblong leafletsWhat looks like a wiry twining vine is one fern frond that never stops elongating - the rachis twines up trunks 90 to 100 ft, hung with SMALL (1-2.5 in) oblong, blunt, smooth-edged leaflets, jointed so they snap off leaving stubs on the wire. Fertile leaflets carry a fringe of tiny finger-like lobes. Small unlobed leaflets in Florida is this fern; large, deeply cut, lacy triangular leaflets is Japanese climbing fern; hand-shaped palmate leaflets is the NATIVE Hartford fern - leave that alone.
- Cut a skirt, then treat the ground matThe standard Florida method: cut every climbing frond in a band around the trunk at about waist height (the 'hula skirt' cut). That severs the canopy mat, which browns and drops over the following weeks and immediately breaks the fire ladder - but it does not kill the plant, which regrows from a tough surface rhizome. Follow up by treating the ground-level mat and the regrowth with a foliar herbicide whose label lists your site, and expect to come back for several years.
- Do not disturb fertile fronds on a dry, windy dayThe fringed, spore-bearing leaflets release millions of dust-fine spores that ride the wind for miles. Cut and treat when the air is still and the foliage is damp where you can, bag any material you carry out, and wash tools, gloves, boots, and vehicle tires before you go anywhere else. Sanitation is a real part of control here, not a formality.
Key signs- Wiry fern fronds twining up trunks and shrubs into the canopy
- Dense mats blanketing shrubs, cypress domes, and tree islands
- Fringed fertile leaflets - the spore source
- Small oblong leaflets that snap off at a joint, leaving stubs on the wire
Dry season & cold snaps (cured fuel, not control)
Dec to Apr, every year- Brown mats are more dangerous, not lessA hard cold snap or the Florida dry season browns the outer fronds, and the mat cures into a light, dry, extremely flammable blanket draped from the ground into the treetops. The rhizome underneath is unharmed and pushes new fronds as soon as the weather turns. Brown fern is not dead fern, and it burns far more readily than green.
- Treat cured mats near structures as wildfire fuelDry-season mats near homes, fence lines, and pine or cypress stands are a wildfire problem before they are a plant problem. Cut skirts to break the vertical fuel continuity, clear cured material away from structures, and coordinate with your county or the Florida Forest Service before any prescribed burn - fire alone does not control this fern and can push it into the canopy.
Key signs- Tan, cured, highly flammable mats hanging from ground to canopy
- New green fronds pushing from the surviving rhizome
- Fuel continuity from ground level into pine and cypress crowns
Hazards
Canopy Smothering & Tree CollapseSeverity High DisordernowEverglades tree islands and cypress domes are the classic case - the same mats that smother the understory eventually pull the canopy down.
Shrubs and young trees buried under fern, mats spanning from one crown to the next, bent or leaning trunks, and dead standing trees inside a solid fern blanket.
Cut climbing fronds at waist height to release the trees, treat the ground mat with a labelled herbicide, repeat for three to five years, then replant with native ferns, shrubs, and wetland plants.
Never plant or move it; find and treat small patches before the fern reaches the canopy, which is the point at which control gets expensive.
The ecological hazard, and it is unusually severe: the fern roofs whole stands in a lacy blanket that shades out the understory, and its accumulated weight bends, breaks, and topples mature trees. Where it takes an Everglades tree island or a cypress dome, it can flatten the forest structure entirely and leave a single-species fern mat behind.
Fire Ladder & Wind-Borne EmbersSeverity High DisordernowIn Florida this is the reason the 'hula skirt' cut comes first in any control plan: it breaks the fire ladder the same day, even though it does nothing to the rhizome.
Continuous fern fuel from the ground into the treetops, tan cured mats draped over shrubs and trunks, and infestations next to homes, fence lines, and pine or cypress stands.
Cut every climbing frond in a band at waist height so the canopy mat dies and drops, then treat the ground mat with a labelled herbicide over several seasons. Do not attempt to burn it out - fire does not control it and can carry it into the crowns. Coordinate any prescribed burn on infested land with your county or state forestry service.
Never plant or move it; cut skirts around trunks to break the vertical fuel continuity before the mat reaches the canopy; keep cured mats clear of structures.
The fern's mats form unbroken fuel from ground level into the crowns, so a surface fire that would have burned harmlessly through the understory climbs into the canopy instead and becomes a destructive crown fire. Worse, burning fern fragments are light enough to lift on the wind and start spot fires well ahead of the flame front, which makes fires on infested land far harder to predict and contain. Cured dry-season mats are the most dangerous state.
Wind-Borne Spore SpreadSeverity High DisordernowThis fern's spores are the reason a cleared property gets re-infested from miles away.
Its fertile leaflets are the fringed ones, and in south Florida they are produced year-round, so there is no safe season - work in still, damp conditions, bag what you carry out, and wash boots, tools, and tires before leaving the site.
Fertile (spore-bearing) fronds, new infestations far from existing patches, and spread following equipment or pine-straw movement.
Limit spore spread through sanitation and timing, kill the rhizome with repeated herbicide, and follow up for several seasons.
Avoid disturbing fertile fronds in dry, windy weather; clean tools, clothing, and equipment; don't move contaminated material.
Why it spreads so far and resists containment: it produces vast numbers of tiny wind-borne spores that travel long distances to found new infestations, and they cling to clothing, equipment, and machinery (and can contaminate harvested pine straw), while a tough rhizome resprouts after cutting.
Mistaken Identity (the native Hartford fern)Severity Medium DisordernowRange is the quick filter: Old World climbing fern is a central-and-south-Florida plant, and the native Hartford fern grows far to the north of it.
Where the two cannot overlap, geography settles the question - but check the leaflet anyway.
Hand-shaped, palmately five- to seven-lobed leaflets like small maple leaves, on acidic, moist, sandy ground in the Appalachians and Northeast - that is the native, not the invader.
If the leaflets are palmately lobed, stop and leave the plant alone; report the find to your state natural heritage program if you like, and check your state's protected-plant rules before touching it.
Identify by leaflet before any cutting or spraying: small smooth-edged oblong leaflets in Florida is the invader; large lacy triangular leaflets across the Gulf South is Japanese climbing fern; hand-shaped lobed leaflets is the protected native.
Not every climbing fern is an invader. The United States has one native climbing fern, the Hartford fern (Lygodium palmatum), which is uncommon and legally protected in several states, and it is easy to cut or spray by mistake if 'climbing fern' is treated as diagnostic on its own.
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