Saw Palmetto Needs Its Saw Sharpened

Serenoa repens

(Sereno Watson was an American botanist.   Repens means lying down.)

Arecaceae

Today’s sweaty trek was a lap of the Kiplinger Natural Area in Stuart with Beautyberries in purple splendor and species of Chaffheads putting on the purple as well.    The sun flecks through the pines lit up the Saw Palmetto fronds like stage lights, so what the heck, today it’ll be the dominant species around here, Saw Palmetto.

Sabal etonia, Scrub Palmetto, is similar but toothless.  By John Bradford.

Being everywhere and familiar to all, Saw Palmetto is festooned with Google-ish info and some mis-info.    We’ll knock off the uber-documented facts expediently,  knowing you can explore further on the Internet, and then ponder a couple less-obvious palmetto puzzlers.

Palmetto leaf wax, electron microscope image, by Dr. Bob Wise, Univ. WI

Well Known Stuff:

1. Saw Palmettos come in silver and in green. The silver comes from wax granules making the leaf reflective and sun-tolerant.   Green individuals have less sunscreen.  The species grows in habitats ranging from full sun to shaded, so it makes sense to have populations mixed for this character.   Some sunny types,  some shady characters. Diversify, or at least that’s how I see it.  The wavy covering can become discolored with black  Meliola fungi, or from sooty mold.
2. The so-called berries (drupes) are an industry in Florida amounting to a harvest of over 7 million kg/year.  There’s a long-standing history of application for prostate health.    Formal scientific studies seem to fail to confirm benefits, although the market abounds.

 

Fruits and ant, by John Bradford

Saw Palmetto “prunes” must have been good for Jonathan Dickinson, shipwrecked at Jupiter in 1696 and surviving with a small group of castaways partly on dried Saw Palmetto fruits while traveling under life-threatening conditions (five died) up the coast to St. Augustine.   It must have been good for JD’s prostate, because he went on to become Mayor of Philadelphia.

4. Saw Palmettos cook happily in fire, and recover in a jiffy.
5. You can make cool darts and dart launchers from the leaf stalks, but that is beyond the scope of today.

Scorched, and on the mend, by John Bradford

Weirder Stuff:

3. Saw Palmetto clones can live a long time by rhizomatous spreading and branching, even if individual above-ground shoots perish or burn. Take a guess.   Botanist Mizuki Takahashi and collaborators recently compiled evidence suggesting maybe 10,000 years.  That’s almost back to the Pleistocene Epoch.    I could eat Saw Palmetto fruits from the same clone as Jonathan Dickinson, but I don’t want to.   He and I agree they are revolting. I’d rather eat a pickled prostate.

4. The roots have air channels, hollow pipes conducting air who knows how deep into the underground. Down-bound air channels are common in marsh plant in suffocating waterlogged soil.  Perhaps my ignorance is showing, but Saw-Palmetto is the only example of rooty air ducts I know in a scrub-dweller.   The species, however, is not restricted to scrub.   Maybe the air ducts allow the roots to go extra-deep in the seasonally soggy-to-waterlogged pine woods soils where Saw Palmetto rules.    The roots need study by somebody with a shovel and a strong back
   

   Flowers by JB

5. The leaf stalks (petioles) have saw teeth. Duh, everyone knows that.  That’s why it’s called Saw Palmetto.   But why the teeth?   The obvious answer is to protect the palms from animals who might eat it, or might climb into it to eat unripe fruit or flowers,  or might trample it.    Perhaps, although to my outlook it is hard to imagine any animals being a big threat now or earlier in the plant’s evolution, even those giant Pleistocene herbivores mashing around.   But you never know.   In any case to go a bit beyond, any other potential benefits from the dentition?   Maybe:

Although I’ve never heard it said about Saw Palmetto (perhaps missed it), I have seen speculation that the Saw-Grass saw blades blow in the wind to slice and dice competing plants.   Makes sense for Saw Palmetto.  The leaves last 3-3.5 years, too long to tolerate pesky vines encroaching.     Look out across a stand of Saw Palmetto.  Even when the non-Palmetto plants are all entangled, the Palmetto tends to be relatively free.

Saw Palmeto is most closely related to the Paurotis Palm, which has big petiole teeth.   Those on Saw Palmetto may be more or less vestigial from big-tooth predecessors.

Prickles by JB

The teeth come in varied shapes, the biggest and best hooking back.   The leaf blade is a big sail attached to a long flexible petiole with those recurved teeth.  With its blade twerking in the wind, the sawtooth petiole would almost have to snag and yank any vines it contacts.

Why are these prickles so tatty?

Evidence that that might (repeat, might) be true comes from a magnified peep at the teeth, especially near the tops of the petioles, where the teeth tips sometimes appear abraded and frazzled as though worn out.  A dull saw, perhaps?

The rare Kiplinger prostativore, snapped by JB

 

 

Gaseous Emanations and Tropical Soda Apple

Tropical Soda Apple

Solanum viarum

Solanaceae

In Allapattah Flats Natural Area yesterday John and George were struck by the conspicuous autumn beauty of a detested invasive weed, Tropical Soda Apple.

Find Tropical Soda Apple in this Gigapan taken by John 11/11 at Allapattah Flats.  (Hint: look near the white posts.)  You can pan around and zoom in and out: Click

Beyond wicked thorns, why is this South American Category I invasive weed the bane of all that’s good?    Those little ”tomato” fruits bear  oodles of hyperviable seeds and are experts at animal dispersal, reportedly moved around by cattle,  feral hogs, deer, raccoons, and other animals, and possibly by birds, as well as in feed, sod,  manure, and other agricultural products, The  spot where we photographed the plant was decorated with raccoon (?) scat.

The weed loves and invades pastures, degrading over a million acres in Florida alone, quite a feat for a South American species unknown in the U.S. prior to the 80s.  There are ongoing efforts to control it with insect biocontrols, hopefully ones not interested in tomatoes, potatoes, eggplants, and many native Solanaceae species.

Cow + TSA = dispersal (and sick cow?)

Tropical Soda Apple differs from other Solanum species in our area by having the young fruits colored like mini-water melons, straight thorns, and petiolate leaves.

Solanaceae are in large part a druggy toxic bunch, despite the edible species, so what about Tropical Soda Apple? Livestock beware! Illness occurs, including brain damage visible upon autopsy.    Cattle do not read veterinary journals; they eat the fruits and scatter the seeds with abandon.  One of the toxins, solasodine, serves commercially as a precursor for steroidal drugs.  It is amazing how little attention there is to human poisoning from such a tempting berry.  The berries are said to be disgusting, which probably has saved children.

The thorns are just plain evil, yet animals do harvest the fruit.  And this ties in with the beauty we beheld yesterday.  The plants were devoid of leaves, no longer very thorny, and festooned with beautiful cherry-tomato-sized golden berries glowing in the late afternoon sun.  They could serve as fanciful holiday trees at the mall, and are eye-catching at a hundred yards.  This otherwise forbidding species apparently lowers its leafy-prickly guard and gooses up its tooty-fruit advertising at seed-dispersal time.  The berries probably become less toxic upon ripening.

The thorny leaves are gone and the golden orbs are ripe for the plucking (but don't) (Photo by JB)

Let’s go a little deeper on that.  Ripening fruits, of which there are many, produce the hormone ethylene.  Ethylene is involved in leafdrop, which is dramatic in the present case.  Bear with us a moment on an academic yet relevant quote from the 1943 Botanical Gazette concerning Soda Apple’s cousin, the tomato.  The title says it all:  “Defoliation of the Tomato Plant as a Response to Gaseous Emanations from the Fruit.”  Plant physiologist John Skok, from the University of Illinois (which Michigan beat yesterday in an ugly contest), tackled a horto-headache with tomato plants: they drop their leaves late in the growth cycle.

The berry opened (photo by JB)

Like Hercule Poirot, he first dismissed some red herrings, diseases and nutritional problems.  Then he revealed the true culprit, in his words,  “defoliation is in part a response to emanations of ethylene or a combination of ethylene and other unsaturated hydrocarbon gases from ripe fruits…”

OK then, ethylene functioning as a hormone induces leafdrop in a species closely related to Tropical Soda Apple.  (In modern agriculture artificially applied ethylene defoliates crops for mechanical harvesting.)  The phenomenon serves a positive purpose in Tropical Soda Apple by removing the thorny leaves while flashing the showy fruits.  Here we have an apparent case of a pre-existing hormonal mechanism enhanced through eons of evolution  to become a specific adaptation for seed-dispersal in TSA.  Not bad for a debased weed!

 

Allapattah Flats and White Pine Barren Aster

 Yesterday John and George went wildflower-hunting in the Allapattah Flats Management Area in Martin County west of Palm City, and found bugs.  Not just mosquitoes, but also good interesting types.

Web in the morning sun (by JB)

Although not arthropod experts, we can match pictures with the best of them, and our creature identifications come from highly scientific picture-book flipping.  Do not bet excessively on them.  We learned that the Female Golden Silk Orb Weaver Spider makes mighty strong silk (which we experienced), is larger than her puny male, and has only a minor bite (which we did not experience) despite her arachnophobia appearance.

Female Golden Silk Orb Weaver (by JB)

 We learned further that the Salt Marsh Moth Caterpillar may occupy Dogfennel (Eupatorium capillifolium) in abundance.  It reportedly extracts toxic alkaloids from Eupatorium, one of its favorite host genera. (Eupatorium toxins killed Abraham Lincoln’s mother, although she probably did not eat caterpillars, and that topic is for another day.)  The caterpillar wiggles nervously when approached, then drops abruptly from its branch in clear annoyance. How does the caterpillar scatter across a large meadow of Eupatorium?  The species can wind-sail on a silky “parachute” when small, and when older they disperse overland.

Salt Marsh Moth Caterpillar on Eupatorium before dropping (by JB)

The adult Salt Marsh Moth is white with dark spots, having some yellow coloration in the male.  It is not particularly a salt marsh dweller.

Let’s get to a plant.  One of the more striking species at Allapattah this week was White Pinebarren Aster (Oclemena reticulata, aka Aster reticulatus), a species distributed mostly to the north of our haunts, and not found much south of Lake Okeechobee.  A quick look at the flowering dates on herbarium specimens shows most flowering is in the Spring or early Summer, then blossoms seem to wane in Summer, with a second blooming period in the Autumn.

Oclemena, yellow phase (by JB)

Here is a perfect example of a species whose flowers change color, placing it in the company of Mahoe Hibiscus, Rangoon Creeper, other “Aster” species,  and scores of  additional examples in many families.    Flower-color-changers seem typically to go from a light coloration, often yellow, to reddish.

This occurs in Oclemena in the disk flowers, the small flowers packed together at the center of this Composite flower head, that is, the eye changes from yellow to burgundy.   This is not likely to be mere decline with age, but rather a signal to pollinators of a change in floral status.  Many flowers signal reward availability to pollinators with changing color.   That color change accompanies diminished pollen or nectar availability is well demonstrated.  Moreover, presumably innate preference for “reward now” coloration occurs in bees, butterflies, and additional insects.  Even more remarkable, researchers have trained butterflies to alter their behavior based on color in relation to rewards.  Pavlov’s Swallowtails.  Yellow is a pervasive bee-advertising color while reddish tones are not.

The "we're closed" phase (by JB)