Blechnum serrulatum (Telmatoblechnum serrulatum)
(Blechnon is Greek for fern. Serrulatum refers to tiny toothlets on the leaf margins. Telmato denotes wet habitats.)
Blechnaceae
There’s nothing more enchanted than bright morning in a cypress swamp during the dry season. The habitat is open, easy to navigate, bugless, and decorated with colorful lichens from rose to battleship gray, asters in bloom, and mossy hues a Leprechaun might recognize.
The biology is enchanting too, seeing cypress knees with spongy growing tips; seedlings seizing the day under the leafless canopy; northern needleleaf with ants; and a dozen plant species huddled on the bald cypress above the highwater line.
So many wonders, yet time and space force a choice. Swamp fern looks like “any old” fern, so what’s swampy about it? The fern shows at least three curious adaptations to life with its roots submerged some months and desert-dry other months. Being equipped for both extremes give the species a competitive edge, in charge where purely aquatic plants would fry and where purely dry-land plants would drown. Sun or shade just fine.
Wet and Dry Adaptation 1. The leaf stalks have veins embedded among air pipes extending from the high dry leaves down into the intermittently submerged regions.
Wet and Dry Adaptation 2. When the fern perches on a bald cypress above the high-water line, the plant is not permanently an epiphyte unable to reach the earth. Look closely…like a little banyan, it drops rhizomes and roots from its elevated base down along the cypress trunk and into the soil at the host tree’s base.
Wet and Dry Adaptation 3. This one requires speculative interpretation. When the fern sits directly on periodically flooded mud it can build itself a pedestal made of a vertical cluster of slender rhizomes bound together into a spongy fascicle by a fibrous meshwork of roots.
The pedestal lifts the fern above the flood when necessary, and looks like it collects debris and microbes in its network of nooks and crannies. When the water is low, the pedestal becomes a reservoir of moisture and nutrients.
Among the blackened dead yet fibrous roots are living roots looking like they harvest water and nutrients from the spongy pedestal through which they creep.
habitatsp@aol.com
December 29, 2018 at 9:39 pm
Hey George,
Very cool piece on the swamp fern.
BTW, I hope that when the day comes that you retire, that you’ll continue these wonderful blogs. 😊
BTW, one of my students who took a recent FL Master Naturalist course was hoping to take your spring class. I hope he got in – nice young man – Dane Boggio.
Wishing you a great 2019!
Chris
George Rogers
December 31, 2018 at 11:10 am
Hi Chris, Nice to hear from you. I’m sure Dane can get in. The class filled and then was expanded a couple times. If he tried while it was full he may think he is blocked, but I added a second day i order to accommodate all takers, so no problem…and he is welcome to contact me for help.
theshrubqueen
December 29, 2018 at 10:20 pm
I was so intrigued by the pictures I had to read the post twice!
Russell Owens
March 22, 2019 at 3:23 pm
I saw a swamp fern in the Loxahatchee National Wildlife Refuge that had the sori spread apart with some distance from the axis. Does this happen often?
George Rogers
March 23, 2019 at 10:08 am
Well, not to my knowledge, but I’ve seen other major mutations in the leaves.