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Cryptic Invaders, Elephant Salad, and the Africanization of American Grasses

05 Nov

Pennisetum purpureum (Elephant Grass, Napier Grass)

Phragmites australis (Phragmites, Reedgrass)

Saccharum giganteum (Plume Grass)

Tall and showy in the breezy autumn sun are those super-sized grasses rising from the marshes, shores and roadside ditches.  Three striking grasses of local wet habitats may rise together in the hot Florida weather, but they don’t have much else in common.  Time for a nod to Elephant Grass, Phragmites, and Plume Grass.

This trio is easy to sort out visually (and see notes at end of article for more details).   The flower clusters of Elephant Grass look like bristly tan hotdogs.  That’s a gimme.  The Phragmites inflorescence in Florida is a bushy panicle with droopy feathery side-branches.  The Plume Grass inflorescence resembles that of Phragmites but is nearly leafless below the inflorescence; the inflorescence branches are stiffer; and the spikelets have awns (needlelike wires at the tips), which are missing in Phragmites.

Each of the three has its own peculiarities:

1. Phragmites is a scary example of subversive bioinvasion.

2. Plume Grass has a double-habitat secret identity.

3. Napier Grass may propel your great-grandchildren’s monorail.

Phragmites. (I have forgotten who took today’s grass photos.)

Is Phragmites native?  Now that’s a loaded question…with no simple answer.  Contrary to some assertions, some Phragmites is native to North America.  Preserved U.S. remains are thousands of years old.  Looking more broadly, Phragmites occurs around much of the world as a mind-boggling species complex revealed in its intricacy by DNA studies.  Botanist Kristin Saltonstall has documented what’s going on here.  (CLICK for details)  There are 27 genetically distinct Phragmites strains, 11 of them endemic to North America.  The most common U.S. strain, known as “M,” probably invaded the U.S. from Europe via southeastern seaports after around 1910, and has snuck quietly but aggressively throughout much of the original North American Phragmites range and beyond.  This is the main invasive strain pestering Europe.  Another strain, the one in Florida, is known as “I” and occurs additionally in South America and in Asia/Australia.  Its original nativity and ultimate classification are not clear, although Saltonstall clearly suspects it to be an old non-native introduction in the U.S.  So, to draw upon some elegant DNA work, is the Florida Phragmites native?   Probably not.  (There are additional taxonomic notes at the end of the article.)

Phragmites stems are straight and strong, giving them ancient and modern uses, with applications as diverse as hut construction, mats, reed boats,  flutes, bagpipe components, “cigarettes,” and arrows.   I make primitive bows and arrows, and have tried Phragmites shafts, which are lightweight and fragile.  Although I have not looked into the matter seriously, I think pre-European Phragmites arrows were generally fitted with reinforcing wooden tips, as shown in Primitive Archer Magazine, from which this photo came:

Ranging from Long Island to Texas and Central America, Plume Grass is elegant in the autumn, looking like a garden species.  Well it actually DOES look like a garden species, especially the related Eurasian horticultural selection Ravenna Grass.  It is likewise related to and similar to Miscanthus known to some as pretty garden grasses and to others as loathsome bioinvaders.  Miscanthus sinensis has shorter flower stalks and longer leaves (the leaf tops reaching the bases of the flower clusters.)

Plume Grass pluming

Where does Plume Grass grow?  To a Floridian, the answer is it swims with the gators. (CLICK for a dandy Gigapan by John.  Find the Plume Grass.)  But what about to a hillbilly like me?  There’s Saccharum giganteum near my parents’ old home in the foothills of the Smoky Mountains, in Smoky Mountain National Park, and down the other side into Tennessee. (To be honest though, it is not fond of high elevations.)

This is getting long so we better hurry along to our third super-sized grass, Napier Grass or Elephant Grass.  This African species, reportedly munched by elephants, likes South Florida.  Driving from Jupiter to Stuart along I-95 yesterday I lost count of the clumps.  Any Floridian who drives a car has seen this jungle-maker.  You could hide an elephant in it.  Brought here as a fodder, Napier Grass threatens to take over the state as one gigantic rhizomatous lawn 15 feet tall.   And what a complex relationship with humans:  if you think it may help feed the world you might be interested in the named and improved pasture selections.  If you think it may take over the world you might like to burn it.  Good idea!  As biofuel of course.  This stuff makes Switch Grass look wimpy.

Napier

Setting aside arguments having to do with ethanol per se, why not put all that green to good use before it smother us?  Then use the corn to make corn flakes.  Even better,  Napier Grass takes up nutrients, including notably phosphorus, from eutrophic waters and from contaminated soils.  One objection to this approach is that, hey, don’t plant an evil invasive weed, but isn’t it too late to worry about that?  We can harvest all the Napier Grass we want from what’s already with us.

After the article was posted, my friend Mary Hart sent this winter wonderland photo of Phragmites near her home in Worcester, U.K.,taken in 28 degrees in January 2012, reminding us that the species has become in places a critical nesting site and food source for water birds.

Phragmites across the Pond (and across the canal), in Worcester, U.K., January 2012, sent by Mary Hart.

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Notes:  Phragmites has the ligule small (1 mm vs. > 2 mm in Saccharum), leaf blades not auriculate (as opposed to Arundo and Hymenachne) and without the light basal coloration characteristic of Arundo. The internodes are pubescent (vs. glabrous in Neyraudia) and the lemmas are glabrous (vs. pubescent in Neyraudia).

This is no place for a pseudo-taxonomic revision.  But for a thumbnail:  According to Bernd Blossi at Cornell, several characteristics distinguish the several endemically native Phragmites strains (collectively subsp. americanus) from the introduced “M” (subsp. australis).  Subspecies americanus has deciduous (vs. persistent) leaf sheaths, ligules > 1mm long (vs. shorter), smooth shiny stems (vs. dull and rough),  reddish or other-colored  (vs. tan) stem bases, low rhizome density,  slow colony expansion (vs. rapid), and round rhizomes < 15 mm in diameter (vs. thicker and flattened).  Type I (subsp. berlandieri) of uncertain nativity and unsettled taxonomy shares shiny stems with subsp. americanus, but has the persistent leaf sheaths and short ligules (< 1 mm) associated with subsp. australis.  Subspecies berlandieri has been lumped into a broader segregate species  P.  karka in some interpretations.

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3 Comments

Posted by on November 5, 2012 in Elephant Grass, Phragmites, Plume Grass

 

Tags: , , , , ,

3 responses to “Cryptic Invaders, Elephant Salad, and the Africanization of American Grasses

  1. Mary Hart

    November 6, 2012 at 4:25 am

    I can look out of my window towards the canal and see a clump of Phragmites communis (?) by the canal bank!

     
    • George Rogers

      November 7, 2012 at 9:14 am

      And the photo is now in hte article. Beautiful.

       
  2. George Rogers

    November 6, 2012 at 7:06 am

    Mary, While looking at images Wrekin Hill I ran across multiple photos of reed beds in your neck of the woods. How many species can I write about in Palm Beach County which you too can see right there? Maybe that and Dandelions…

     

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