Small Leaf Climbing Fern
(Lygodium means flexible. Microphyllum means small leaf)
This morning John and I pursued minor projects in Kiplinger Wildlife Preserve, in awe of the imperialistic Small Leaf Climbing Fern, a gift that keeps on giving from the Old World, first recorded in Florida during Elvis, escaped during the Beatles.
Its massive growth is matched by massive attention to its peskiness on the Internet. No need to be the millionth post on that. For those unfamiliar with the problem, probably not Florida residents, this fern can smother a tree in the wink of an eye, climb high into the canopy, spread fires, and even reportedly snare a deer.
Rather than rant on about invasiveness, it might be more interesting to explore the biology of this super-weed. Two invasive Lygodiums compete to own Florida: Lygodium microphyllum is common around Palm Beach County. Lygodium japonicum is more prevalent northward. Farther north still across the Florida state line comes the native Lygodium palmatum. The invasive species grow like lightning, L japonicum as much as three inches a day.
These clambering vines are not really vines. The entire aboveground climber is a leaf, a frond, although division into leaflets along a stringy center gives the false appearance of a leafy stem. But no. The true stem is at or below ground level, launching the immortal ever-lengthening leaves skyward to go forth and multiply. The individual leaves climb 30 feet or more.
And here is how: The tip of most any fern leaf (frond) is a curl called a crozier. Normally the crozier uncurls, and that’s that. But this is no normal fern. In Lygodium the crozier never uncurls. It just keeps on lengthening the leaf. The leaf portion behind the crozier stays bare like a thin twig and forms a hook. The hook rotates on its own, and also blows in the wind. All this twistin’, and hookin’; and blowin’ is an effort to hook onto something to climb. When that happens, let the rise ensue until the leaf snakes to the top of the host, then the hooky business resumes seeking a taller host. Upsie daisy! Below the hooky region the older regions broaden out into the characteristic leaflets, hundreds of them like lights bulbs strung on a wire around a used car lot.
If a leaf extends high up into the tree and then breaks off, oh my, what a disaster. But no, wait, there is a safety mechanism. Along the leaf are fuzzy rust-colored buds ready to grow forth and save the day.
That the leaves rise directly from the “roots” allows direct immediate nutrient interchange between leaf and “root.” Such efficient root-leaf commerce has turned out, it seems, to allow for especially enriched roots to cope with bad soil, not to mention fuel that magical leaf growth.
Botanists have shown…at least under some circumstances…the plants to grow equally well in bright sun and deep shade. They do not care. Wet places are favorite habitats, pine woods will do, and even sometimes dry scrub. It’s all good! Flooding seems to boost spore production, and that is a deliberate segue:
Ferns reproduce by dust-sized spores blowing in the wind. One individual Climbing Fern can produce astronomical numbers of spores. There has been concern that workers exterminating the fern get their clothes contaminated with spores, spreading the pest unwittingly, helping it rather than wiping it out.
Watch the hook helped by wind seek a new host to climb: CLICK
When the baby Climbing Fern grows from the spore it matures as female with a trick. She releases hormones to make the nearby babies mature male as automatic mates.
If that fails, the female develops its own sperm-producing organs and fertilizers itself.
There’s no stopping Climbing Fern.