Three-Awn Grasses Are Negative Campaigners

Aristida sp.


Today John shot a new panoramic photo (gigapan) in Jonathan Dickinson State Park to continue documenting recovery after a prescribed burn.  That was before we left the IPad in the woods in the thundershower.  (No worries—it had a happy ending, and compelled a second trip to a lovely park.)


Monoculture.  See notes on photos below.

Prescribed burning keeps much Florida acreage in a fire-dependent  “early” successional stage.  A recurring thought overlooking such fire savannas is the prevalence of grasses, as opposed to understory plants from other families.  Several reasons, not of much interest today, help explain this, including fire-resistant rhizomes and the ability of grasses to rise from basal growth points after the tops succumb to  flames, to deer, or to John Deere.  Many grasses, including three-awns,  have what’s called C4 photosynthis, a special advantage in hot climates.

Let’s zoom  like a gigapan on one component of grassish domination… monocultures of just one grass genus, Aristida.     Aristidas are a big bunch, over 300 species around the warm world.   Why so successful?

To start with a fun if not important answer, their name gives a clue about one advantage, they are three-awn grasses.  An awn is a bristle, and each spikelet (seed-head) has three of them.   What’s so great about that?

So many great things!   Herbivores probably don’t much cotton to needle salad.     Moreover, associated with the “seeds” (achenes) the awns catch on fur, wind, and water to disperse.  Also they may help lodge against other vegetation or take hold on the soil.   That awns serve diverse functions is hinted by their diversity in abundance, lengths, orientations,  postures, shapes,  barbs, stiffness, and probably responses to moisture.


Awns are three, easy ID

In some species all the awns are coequals, while in others the central awn dwarfs the other two.   Many additional grasses have awns, if not in triplets, and looking beyond Aristida, awns contribute to photosynthesis and help position the seed for optimal water uptake.   To drift  into left field, I wonder if they absorb water or nutrients.

Speaking of nutrients,   how does a monospecific understory of grass secure the nitrogen it needs?    In contrast with grasses,  legumes and many  other plants have nitrogen-fixing nodules.  And frequently free-living soil microbes contribute, as does decaying organic matter.


Doing the twist

Now we could do the obvious and fret over how meadows of grass get the nitrogen they need to survive as the fittest.   But turn the beat around… and take a page from the presedential politics playbook.   There are two ways to get ahead,  rise up on your merits (boring), or tear down the opponents.

So, in honor of 2016, how do Aristidas manage to become President of the Park?   They are negative campaigners.  The explanation requires some shameless speculation and extrapolation of limited research.   Just read on:

Aristidas are early-succession plants, pioneers.  Any ecology book tells us that pioneer species soon give way to different replacement species, these soon booted out by bigger better species, and so forth.    Another name for pioneer species is weeds, and some very talented weeds are legumes with their nitrogen-fixing nodules. Legumes are all over Jonathan Dickinson Park, but not among the Aristidas.  Why don’t legumes and their power-nodules move in there?

Aristidas filibuster.  They expand and overstay their fair turn in the succession parade.   Some of their advantages are obvious, such as those awns, and tough rhizomes, but there’s a more interesting trick up their sleeves.   Three-awns repulse their would-be replacements by destroying the nitrogen-fixing bacteria critical to the interlopers.   Aristidas loathe legumes, turning the pretty pink nodules to black.


How’d you like a mouthful of that?

Of course if you deprive the foe of nitrogen you do need to get your own.   Three-awns  can probably acquire it rapidly after a fire, but so much more intriguing is the increasing research on nitrogen-fixation by grasses with the assistance of bacteria different from the ones the grasses suppress.    Purple three-awn  has associated with its root sheath nitrogen-fixing bacilli belonging to, or similar to, Bacillus (Paenibacillus) polymixa, perhaps cryptically contributing to the grasses persistence in the face of competitors.

Time to wind down,  but let this then be a lesson to all political hopefuls.  You too can grow up to be President.  Be stubborn.  Be bristly.  Be toxic.  And most importantly,  have grass-roots support.

Note on today’s photos.  These are from a project John and I worked on ca. 2007.   I do not recall who shot which.  We know what the species are but that info is suppressed as a distraction.  The essay concerns ecology, not taxonomy.


Posted by on September 23, 2016 in Uncategorized


Caribbean Apple Cactus

Harrisia fragrans



Howya like them apples?  Today’s photos by John Bradford.


William Harris was a botanist/horticulturist in Jamaica.  Fragrans means fragrant.

This blazing day went to the purpose of searching the western margins of Savannas Preserve State Park and nearby near Jensen Beach, Florida, for the rare and probably-not-native Agave neglecta.   Let’s neglect the agave for today’s story.   Searching for an agave sounds like a mission to Mexico, and the scrubby ridge along the Florida East Coast RR is so high, dry,  bleached,  white,  and glaring it hurts the eyes. (Of course that may have had something to do with a prior trip to the eye doctor today. Never visit scrub when dilated.)   Today’s motorized posse were John, Savannas SP Biologist Doug Rogers, and George Rogers.

The joy of a mission is the journey, and today’s journey had a desert ambiance reinforced at every turn with multiple species of agaves, prickly pear cacti,  and best of all,  Caribbean apple cactus  I’ll bet within a stone’s throw of where Florida botanist John Kunkel Small discovered it in 1917.


Traditionally Harrisia cacti in Florida comprised a trio:  H. fragrans confined to the area we visited today,  H. simpsonii at the southern tip of the state, and H. aboriginum on the Gulf Coast.   Studies have suggested interpreting H. simpsonii and H. fragrans to be a single species.

The name H. aboriginum hints at a fun fact—Harrisia cacti in Florida have association with pre-European middens, and the tasty fruits must have been a pleasure to the earliest humans in town.   Did humans long ago perhaps bring Apple Cacti from the Caribbean, as they might have brought papayas, agaves, and who knows what?



In an evolutionary sense, Harrisia flowers were probably originally bat-pollinated, but hang on, even though they look bat-ish divergence from such possible beginnings seems to have occurred.  Botanist J. R. Sandoval and E. M. Ackerman recently studied  Harrisia portoricensis in Puerto Rico, and their observations are puzzlers:  Animal visits were infrequent, and the flowers are not matched to the needs nor ways of bats.   Those botanists, noting that most Harrisia species live on Caribbean islands, suspected that hurricane-disruption of bat populations forced the cacti to diversify their pollination help.

That is one fancy wind-pollinated flower! Maybe.   Illustration from Britton and Rose, Illustrated Cacti,  public domain via Creative Commons.

Disappointingly though, they found the flowers to be not great matches to hawk moths either, although hawk moths do pitch in. The most important floral visitor was  wind, causing self-pollination by knocking the pollen-making stamens and pollen-receptive stigmas together in the same flowers.  They called it a “wind-aided self-pollination system.”   Island dwellers learn to make-do.

Pollination study of the  Apple Cacti here in Florida might be fun and illustrative.  We don’t have much or any (?) bat-pollination. Biologist Jon Moore found beetles in the blossoms.      We have plenty of wind.

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Posted by on September 17, 2016 in Uncategorized


Baldwin’s Spikesedge, King Tut’s Nibbles, Tasty Horchata, and the Poisoned Path

Eleocharis baldwinii

(Eleocharis translates loosely as “graceful marsh-dweller.”  William Baldwin was an early American botanist active in Florida and several additional places.)

Cyperaceae (Sedges)

Despite the substantial size of the Sedge Family, we don’t munch many.  Chufa flour is familiar to those who enjoy the Mexican beverage horchata, which to me evokes childhood memories of (nonchocolate) Ovaltine.  Chufa  is more familiar to Floridians as the pesky weed known locally as yellow nutsedge,  Cyperus esculentus. “Esculentus,” meaning edible, is a clue to the past.   Chufa’s culinary history stretches back  4000 years in Africa, especially Egypt.  I can go behind my house and yank up a tasty snack King Tut enjoyed so long ago (but I won’t).  Let’s just say, “when life gives you nutgrass, make horchata.”


Baldwins Spikesedge, with flowery spikelets on vertical branch tips. By John Bradford.

Another foody sedge is the so-called water-chestnut, which has zero to do with chestnuts and much to do with Chinese cuisine.  It is Eleocharis dulcis (dulcis = sweet), and is a segue into today’s continued exploration with John of the Kiplinger Natural Area in Stuart, Florida.  We ate no Eleocharis, but we tread upon it, Eleocharis baldwinii that is.

This little spikesedge has at least 3 fun features:

Fun feature 1.  Although most of the flower clusters (spikelets) are elevated like spear tips atop vertical stems, some strictly female spikelets sit directly at ground level.  In a wind-pollinated species, those lowdown flowers out of the breeze are tough to explain, and why female?    Here is a completely untested notion:  most of the raised spikelets pass on to an odd fate described below.   So maybe the shorties escape destiny and can catch wind-borne pollen sifting down from above, assuring some “normal” pollination.


Female (seed forming) spikelets remain at ground level.  By JB

Fun feature 2.  This species is amphibious.    It can grow lushly on moist soil or can live submerged, even fairly deep.    In water it becomes  stringy  resembling an imaginary seaweed.  Submersion spreads seeds and drowns  terrestrial competitors.   Emersion snuffs  aquatic competitors. Life is good.

Fun  feature 3.   Our species forms monospecific lawns in disturbed moist places, loving paths and dirt roads, weed-free.


Baldwin’s spikesedge-covered path in Kiplinger today.   Where are the other-species weeds?

How does it spread?  Well, there are seeds (technically achenes) dispersed in water and birds.   And, more interestingly, the species is “viviparous.”   That is, the spikelet-bearing upright stems elongate until they flop over back to the ground by their own weight.  (Gardeners have seen the same in “walking iris” and similar in “spider-plant.”)

When the tip of the spikelet strikes the earth it spawns a new baby plantlet, thus this species “walks” across the mud.    Some of that growth may come from seeds germinating in the spikelet touching the soil, but I suspect the sproutage to be unrelated to the seeds, or a mix.


Baby on a wand.   The wand is a stem that got elongate, bent to the ground, and sprouted that baby.

Walking helps explain how the plant spreads, but any suburbanite with a St. Augustine spread would envy the spikesedge’s freedom from weeds.  How does it do that?   Answer: it makes its own herbicide.


Baby portrait

Earlier botanists noticed how species of spikesedges hold forth in pure colonies, generating a history of research leading to a natural weed-whacker called dihydroactinidiolide.   Spikesedges squelch “the other” sufficiently to generate interest in connection with aquatic weed control.


Posted by on September 9, 2016 in Baldwin's Spikesedge, Uncategorized


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Two Thousand Ways Not to Make a Tire


Solidago species



Scrambling to hop on a plane and zoom up north to son Martin’s glorious wedding to wonderful bride Phoebe, I’m tossing up the blog early this week.   The matrimonial son is a tire engineer…a blog in honor of the occasion. (Phoebe has a cooler job–she’s an engineer who works on explosives.)

While the rest of the nation catches a nostalgic scent of end of summer Labor Day,  in Palm Beach County we’re catching newsy stuff about tropical storms.   But there are  a few subtle whiffs of my northern-bred seasonal instincts. Cicadas say goodbye-summer.  So do the Goldenrods,   making the meadows glow.   And, no they do not cause hay fever.  Naming them, Linnaeus felt just the opposite, the genus Solidago translates loosely as “making whole.”  Not “making sneeze.”

Solidago fistulosa 7 - Copy

Golden glow, by John Bradford

Goldenrods are a complex group with border disputes, about 100 species around the world, mostly in North America. About 20 in Florida.  An abundant and attractive local standout is Pinebarren Goldenrod, Solidago fistulosa.

Everybody likes Goldenrods.   Remember that “goldenrod” page in forms in triplicate?  Gardeners like them to the point of commercial cultivars and articles in “Fine Gardening Magazine.”

Gall Flies enjoy the plants in their own way,  inducing  big spherical galls in the stem.  One  fly is so solidag-o-centric it is named  Eurosta solidaginis.    It is always fun when biological relationships chain to three or more species*:   Chickadees and Downy Woodpeckers see the galls as I see Burger King, and help themselves to the Whopper larvae within.

Solidago fistulosa 5 - Copy



Birds are not the only threats.  Parasitic wasps inject eggs into the gall, which upon hatching devour the creepy maggot and sometimes top off the protein with a vegetable…the gall tissue.  One wasp hormonally forces the fly larva to mature on the wasp’s dining schedule.  Spring chicken!

Now this where it gets truly interesting—as the biologists noted below have determined— these comings, goings, and microaggressions influence the girths of the galls.   First of all, the plant makes a difference, some clones tending to form  larger galls than others.  (Clones can spread by rhizomes into extensive stands.)

But that is just the trailer for the feature attraction.  Size matters in galls.   If in a locality the fly’s only pests are parasitoid wasps, the bigger the gall the more wasp protection the larva experiences.  On the other hand,  if the larva-eating birds are on the scene, the avian predators seem especially drawn to larger galls, being more conspicuous and/or offering larger larvae.   In that case bigger is not necessarily better with the adaptive consequence smaller galls than without angry birds.

Without falling into the silly trap of “plant intelligence,” the complex and dynamic realm of things plants do has blossomed to remarkable in recent years, including the “plant immune system” (Systemic Acquired Resistance).    Goldenrods reportedly  “detect” pheromones from the male gall flies and then emit defensive compounds to repel the female flies.

Solidago (4) edison - Copy

Edison, colleague, and Solidagoedisoniana.”   I took this picture of an interpretive sign at Edison’s Florida house.

Yep, everybody enjoys Goldenrods, and maybe the most fascinating “like” came from Thomas Edison.   Visiting his home in Ft. Myers, visitors learn about Edison’s quest for rubber crops.  After all, his Florida next door neighbor was Henry Ford who had some interest in tires.  Edison tested as many latex-drippy plants as he tested materials for the light bulb,  thousands they say, including a Ficus still on the property, and his primary focus zoomed in on rubber from Goldenrod.   Edison’s experiments  culminated in a breeding program for what was then named Solidago edisoniana (actually S. latissimifolia).

Edison manufactured a few Goldenrod proto-tires and showed them off on a Model-T, but they never panned out commercially, as Brazilian Rubber Trees and synthetic rubber bounced up as better options.  Glad that lightbulb finally glimmered its golden glow.


*Most of today’s gall-related info comes from Dr. Warren Abrahamson at Bucknell University who with collaborators has studied these relationships in depth.

This link concerning freeze tolerance in a Solidago gall fly may interest some.   Cryogenics in the maggot realm.

This link talks about Edison’s rubber program.


Posted by on September 1, 2016 in Uncategorized


Fiddler Crabs, Mangroves, and Leather Ferns Getting Along Famously

Today, John, lichen-student Bill Grow, and I enjoyed  Kiplinger Natural Area in Stuart, Florida.   That is, until a startling thunderclap sent us scurrying like three comical crabs.   Bill’s lichens engendered a symbiotic frame of mind, and a hoppin’ symbiosis  this afternoon involved a trio of salty species.  Delighted we were to encounter the crabs still fiddling a happy tune along the algae-poisoned St. Lucie River.  The crabs were crab-walking, burrowing, and waving their massive claws like a homecoming queen in a convertible, wearing a giant foam finger.

Fiddler crabs

Crab party by John Bradford

And that’s good for the mangroves.   Biologists have repeatedly noticed, in different terms with different points of emphasis, the mutual benefits of Fiddler Crabs and salt-loving plants.  Anyone who visits a mangrove swamp can attest to Fiddler Crabs too numerous to ignore.   Crowds of burrowing scavengers in the root zone of a tree in a marginal habitat must matter, and they do, apparently overall for the better.

Rhizophora mangle 1

Crab habitat by JB

That tidal mud is suffocating to roots. No problem, the crabs are natural rototillers, and their burrows interconnect into subterranean duct systems.   The soil is salty, yet the reticulated tunnels allow tidal fluxes and rainwater to flush out the salts and toxins.

That soil is nutrient-poor, so thank you crabs for gathering, depositing, spreading, churning, and becoming fertilizer.  Research by biologist Nancy Smith and collaborators documented  enhanced White Mangrove growth in the company of crabs vs. crabless losers.

Avicennia germinans 8

Dead man’s fingers by JB

Researchers Erik Kristensen and Daniel Alongi showed the Gray Mangrove (west coast Avicennia marina) to grow leafier seedlings and more “dead man’s fingers” where fiddlers roam.  There’s a hint the Avicennia contributes to the active crab lifestyle beyond the presumed benefit of roots bracing the crab burrows against moving water.  Materials from the happy roots seems to favor microbial growth beneficial for the crab diet of algae and small organic miscellany.

Acrostichum danaeifolium 3

Leather Fern by JB

The mangrove swamp along the St. Lucie River  hosts huge Leather Ferns.  According to biologist Peter Hogarth, the crabs have a hand (or a claw) in this too, their enriched mine tailings are “planting mounds” for baby ferns otherwise in  existential peril if not elevated above the brine.


Posted by on August 26, 2016 in Uncategorized


Mulberry Weed

Fatoua villosa

(Origin of name Fatoua not certain, a surname?, villous means shaggy)


All around the Mulberry Weed the monkey chased the weasel.    The monkey thought it was all in fun…pop goes the Mulberry Weed!

No Friday fieldtrip today.  Displaced by back-to-school meetings.     Contrary to common perceptions, however, meetings don’t scotch botany joy when your guiding principle with plants is, “love the one you’re with.”   The weeds in the parking lot are as interesting to me as any  species.    In tune with such democratic botany, to the right of the door into the meeting hall, in the old mulch among cigarette butts, resides today’s selection spotted during a break:  Mulberry Weed.

A member of the Mulberry Family, Fatoua villosa invaded the U.S. at about the same time as Herman’s Hermits.  The leaves of this Asian novelty resemble those of our native Red Mulberry.   The two are related, but not that related, so the similarity may reflect some combo of convergent evolution and shared genes, a puzzling situation in classification.

Photos:  True Mulberry on left (by John Bradford), Mulberry Weed and cigarette butt today in Lake Worth, Florida, on right.

Fatoua has skitter-scattered from an apparent debut in Louisiana over much of the U.S., mostly in the South, with cameo appearances northward, to the entertainment of northern botanists.   The northward appearances are no mystery, because the species spreads in horticultural nursery material like Measles spreading through 3rd graders.

Fatuoa LW campus

Flower cluster on left, with mixed male and female flowers

Which brings us to the good stuff:    The plants shoot their “seeds” (to be exact, achenes) like shotgun pellets  3 feet or more.    In a crowded plant nursery a Fatoua infesting a flowerpot can rain seeds on its neighbor pots, and they in turn shower more posies in a chain reaction, and then great big trucks ship them all over to pepper the nation.  Buy a nursery plant and you too may gain a Mulberry Weed.  Or a few.

To make infestation easier, this talented weed matures from seed  to flower back to seed in a few short weeks, even when mere inches tall, maxing out at about three feet.

How do those seed shooters work?   In 2003 botanists Carroll Wood and Norton Miller took a peep at it.    The illustrations below are from their work*.  Each inflorescence has mixed male and female flowers.   The female flowers are bizarre. (So are the males but enough is enough.)

A female flower is shown below, with a long hairy style (pollen-receptive organ) rising from the side.  Why displaced to the side?    You’ll see.

Faroua 1

Remove the non-reproductive parts, and the female looks like the illustration below.  The warty “bowl” (developing fruit) to the right of the style hides the single seed preparing to launch.  Note the warts on the cover of the bowl. We’ll see those again.

faroua 2

When it is time to fling, the bowl  explodes its lid open with the seed flying forth like a mortar shell.   The flower shown below has popped its top and shot its seed.  The two halves of the lid now stand vertically like the lid on a jack-in-the-box. You can recognize the ripped-open lid halves by the warts.

Fatoua open fruit

The final drawing shows the projectile seed (achene).

Fatoua achene


*Note: the origin of the illustrations matters.      Both of those botanists were my bosses and mentors long ago and far away, and both are now deceased.   They would have been pleased to share their work.   The artist is Patricia Kernan of the NY State Museum, used with her permission.

Posted by on August 19, 2016 in Mulberry Weed, Uncategorized


Trumpet Creeper Cheats a Bit

Campsis radicans (Campsis means curved, perhaps the stamens.  Radicans means rooty.)


John and I today continued exploring of the Kiplinger Natural Area in Stuart, visited by a curious Limpkin.

Campsis limpkin - Copy

It must be August, with the Goldenrod evoking the summer meadows of childhood.   Among the botanical treats in bloom now is the colorful Trumpet Creeper vine, so showy and “exotic” for a native species.  Those orange trumpets look like something out of a TV special on the Amazon.  Trumpet-Creeper is in the same family as many garden selections, such as African-Tuliptree,  Tabebuias, and Garlic-Vines.

Campsis radicans 4 cluster - Copy

TC by JB

We’re near the southern end of its range which covers most of the eastern U.S., as well as westward and north into Canada perhaps due to human activity.   There are only two Campsis species on Earth,  one in Kiplinger, the other limited to eastern Asia and almost identical to ours.   That’s all there is, there ain’t no more.    Such eastern-North America/eastern-Asia sister-species splits are well known in biology, exemplified  most dramatically by another pair:  American Alligators and Chinese Alligators.

Gardeners please note:  the vine is aggressive, high-climbing, toxic, and irritating to the skin.

Campsis radicans 7 cardinal - Copy - Copy

By John Bradford

Trumpet Creeper is uncommon in South Florida outside of cultivation, and the reason may be our shortage of hummingbirds, the main pollinators.   Extra visitors include bees and butterflies, but studies have shown a threshold of about 400 pollen grains to cause fruit formation, and pollen from the same plant does not work.    In short, a job for a big hungry hummingbird, not a little lightweight bee or butterfly.

Although tough to pollinate, Trumpet Creeper is easy to propagate.  At Palm Beach State College, we grow it from segments of roots.  Thus in nature the vine can probably establish wherever root pieces go, a useful trick in, say, a floodplain where the ground can break apart and float away.

Campsis radicans 6 butterfly - Copy

Hey, I can’t reach the nectar!  (JB)

The stems are odd in structure.    Resembling Poison Ivy, they climb a host tree using tiny clinging roots like centipede feet.    Trumpet Creeper is a structural parasite, reaching great heights freed of the need to make strong supportive wood.     Many readers know that normal woody plants have a green cambium just under the bark to expand the girth of the stem by making strong new wood to the inside as well as new bark to the outside.    Trumpet Creeper, by contrast, makes extra sugar-conducting tissue at the inner core of the stem where there would be wood in a self-supporting species.    In other words, stealing outside support allows the selfish vine to concentrate on fueling rapid growth rather than holding itself up.   (Know anybody like that?)

Campsis radicans 1 close - Copy


The flowers make enough nectar to feed a bird.   Everybody likes nectar.   Those blossoms are to nectar thieves what a bank is to bandits.  Banks need tough guards.  Trumpet Creeper has armed guards too.   To pay its sentries the flowers have nectaries on the outside at the base (on the calyx).  They look like blisters, and feed belligerent ants who presumably protect the nectar-laden floral base from any varmint that may nip a hole and swipe the sweets.

Campsis glands glands - Copy

Little ant-feeder blister glands on the outside of the flower base


Posted by on August 12, 2016 in Uncategorized

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