Ferns that Climb Trees
By Joe Wolf
Polk County Master Gardener
Two closely related ferns that climb are very bad for us.
Vining ferns are fairly rare but there are a number of them.
The two bad vines are another of those plants that have
invaded Florida and now cause great harm to our
environment. As far as I can tell, these are they only two
climbing ferns in Florida. There are other ferns that grow in
trees, for example, the resurrection fern (Pleopeltis
polypodioides) is often seen on the top side of Live Oaks
branches, but they did not climb up the tree to get there.
Old World Climbing Fern
Likewise ferns are found in the boots of some palm trees, but
there are individual plants that have grown in each boot. The two true climbers are the Old
World Climbing Fern (Lygodium microphyllum) and its close relative Japanese Climbing Fern
(Lygodium japonicum).
What is so bad about these lovely plants: aren’t all ferns beautiful? Well yes, they are, but
these particular fens grow very dense and climb very high in trees and shrubs and cover them
until they die. You can have entire forests of nothing but climbing ferns. Furthermore, in the
case of fire, they provide an excellent way for the fire to climb to the
top of the tree and thus spread faster.
Japanese Climbing Fern
There are about 12,000 species of ferns most like to live on the ground,
usually in wet or damp areas, but a few like the ones that cause so
much trouble in Florida, like to climb. Ferns do not have seeds, but
reproduce from tiny bodies called spores. The spores are usually found
in big groups in rows on the bottom side of the fronds. They look like
little dots. Ferns have special fronds that have spores on them; these
are called fertile fronds and are different from
the fronds without spores. Spores being so
tiny easily float on the wind to spread the
plant far and wide.
Japanese climbing fern was brought to this country around 1900
probably as a decorative plant. It is native to eastern Asia from Japan
west to the Himalayas. It escaped cultivation and is now established
Close-up Japanese Climbing Fern
Fertile leaves
in the coastal plain from Georgia to Texas including Florida. In Florida, it is traveling down the
peninsula all-the-way to Miami. It is a perennial (it lives more than one year) that can reach
over 90’ up a tree. The leaves are lacy, finely divided, and opposite each other on the vine.
Sometimes the vines are green, and sometimes orange or black. The fronds turn tan-brown in
the winter but do not fall off the vine. In south Florida, they remain green. The fertile leaves
are usually smaller than the non-fertile leaves and have finger-like projections from the around
the edge. The spores are in double rows on the underside of
the leaf near the edge of the leaf.
The Japanese climbing fern grows well in the sun and the
shade; in disturbed areas like roadways but also in undisturbed
areas. It can grow so dense that it can form a living wall that
kills everything else.
Close-up of Old World Climbing Fern
Fertile leaves
Old World Climbing fern is a native of Africa, Asia, and Australia. It
was first found in Florida in a nursery in Delray Beach in 1958. Since that time, it spread to
about 27,000 acres in 1993 and then to 122,787 acres in 2005. Each little leaflet on each fertile
frond can product over 28,600 spores. No wonder it has spread so fast. It can now be found all
through south Florida from Miami to Hillsborough, Pinellas, and Polk counties and further north
on the east coast. Like the Japanese Climbing fern, it can get to be over 90’ long. As it grows, it
can cover shrubs and trees by twining around branches and trunks. The fern’s stem is dark
brown to black and is wiry. The leafy branches are from 2” to 5” long with several paired
leaflets. The fertile fronds are fringed with tiny lobes of enrolled leaf tissue along the edge of
the leaf. This rolled tissue hides the spores.
Management of both of these pests is similar and equally difficult. Eliminating either will be
multi-year efforts. Vigilance and prompt action are necessary.
Work on this plant only when it is not producing spores (the little dots under the leaves). The
spores are so tiny that they can spread around the neighborhood by clinging to clothes and
shoes, as well as blow around by the wind.
The best method of eradication is to dig up the roots and collect all pieces of the vines. Dispose
of them so they do not spread. On larger patches, herbicides may be necessary. For
homeowners the herbicide of choice has the active ingredient glyphosate. Products with this
active ingredient are: ‘Roundup’, ‘Roundup Pro’, ‘Glypro Plus’, ‘Touchdown Pro’, and ‘Dupont
Glyphosate’. Use a 2% or 3% solution of glyphosate in water. The above products cannot be
used around water; they will kill water animals including fish. Near water, you can use ‘Rodeo’,
‘Aquamaster’, ‘Aquaneat’, ‘Eagre’, ‘Aqua Pro’, ‘Glypro’, and ‘Accord’. You can find some of
these, but maybe not all, in nurseries and big-box stores.
These two ferns are not frequent in the city; however, a friend of mine in Winter Haven pulled
one out of a pot recently. They may not be frequent, but you can find them especially in damp
and swampy areas. Watch for them and remove them if you find them.
To read a long review of the management plan for Florida for Old World Climbing Fern see:
http://www.fleppc.org/Manage_Plans/Lygo_micro_plan.pdf
For more information on the Japanese climbing fern, see:
http://edis.ifas.ufl.edu/pdffiles/FR/FR28000.pdf
For more information on the Old World Climbing fern, see:
http://edis.ifas.ufl.edu/pdffiles/AG/AG12200.pdf