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Bluestem Grasses – Andropogons

29 Oct

Bluestem Grass

Andropogon, several species

Poaceae

Hurricane Sandy and Hurricane Work Obligations thwarted the usual Friday trip this week.  A little alter in time, this morning dawned cold and brightly sunny, and I visited the Sweetbay Natural Area near the Palm Beach North County Airport.  One of John’s and my favorite wet sites with a civilized paved sidewalk.  The cold was compensated by the striking beauty of the horizontal sunbeams lighting up the silvery beards on the various Bluestem (Andropogon and Schizachyrium) grasses.  Those fireworks alone justify an early start.

Splitbeard Bluestem with its split beard (don’t recall who took the pic)

It is not my purpose now to be schoolin’ ya about how to distinguish the Andropogon species.  John and I tried that, and the results are a click away at  floridagrasses.org.

Some readers might agree that locally the Bluestem Grasses can be tough to differentiate.  Whenever you see reference to a “species complex,” watch out for a puzzling network of funny business.   Most of our nearby species belong to the “Andropogon virginicus complex,”  which seems to be diploid, comparatively free of apparent hybridization, and yet often with subtle visible differences between species.

One of the prettiest and most distinctive species is the Splitbeard Bluestem, Andropogon ternarius, which is a tetraploid (has 4 sets of chromosomes) and has a particularly delicate appearance:  tall and slender with big long silvery-white bunny ears (spikelet clusters) displayed on wirelike wands.  It looks like a work of art, and  I always enjoy encountering this exquisite bit of creation.  Gardeners agree.  I recently saw this species for sale at approximately $40 per cell tray.  A seedy variant developed in Florida chiefly for habitat restoration is called “Ft. Cooper.”

The plant world is full of fluffy-puffy feathery wind-dispersal units, but Andropogons are  the ZZTops of the flora.  In fact the name Andropogon means dude with a beard.

You could scarcely design a species more appropriate to wind-dispersal.  The bunny ears bust apart at the slightest whisper, separating into parachute-bearing “seeds” (spikelet clusters) to blow hither and thither.  The microscope view shows what they bust apart into.   The feathery parachute hairs in the photo are of obvious function.  The two long threads (awns) visible in the picture are less obviously useful.  The awns probably catch the wind or bump against adjacent plants and help the bunny ears bust apart.   Also interesting are the two small vertical “daggers” you see flanking the main spikelet.  Those are sterile (seedless) spikelets.    Who knows—maybe they’ve lost their function but the genes that make them have not quit altogether, sort of like the human canine teeth.

Andropogon ternarius spikelet cluster. Center-left is large fertilie spikelet with long awn. Smaller sterile spikelet “dagger” is vertical just center-right. Another awn is visible tilted to the right.

The natural distribution of Andropogon ternarius is roughly the southeastern 1/3 of the US from Florida to New Jersey, Indiana, and Texas.   At least that was where it was is was yesterday.   Sandy may redistribute some bunny ears today.

Split-bearded dudes

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6 Comments

Posted by on October 29, 2012 in Bluestem Grass

 

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6 responses to “Bluestem Grasses – Andropogons

  1. annsbirdventures

    October 29, 2012 at 2:26 pm

    Split bearded! You are so funny!
    Ann

     
    • George Rogers

      October 29, 2012 at 5:45 pm

      Hi Ann, Is it my innate patriotism, or am I really seeing bald eagles up and down the Intracoastal. not ospreys I don’t think, but I’m half-blind.

       
  2. Mary Hart

    October 30, 2012 at 5:00 am

    Wonderful comparisons! My favourite wind dispersed plant is the hazel nut, Corylus avellana – so cheerful in early spring, and the nuts are wonderful.

     
    • George Rogers

      October 30, 2012 at 9:02 am

      Hazelnuts are one of the many reasons I miss living up north….easy to say in October though.

       
  3. mudfish

    October 30, 2012 at 6:31 am

    I was fishing in my kayak the other morning, right across the street from the Park entrance, and saw two eagles. Maybe you can put off the new glasses for another year!

     
  4. George Rogers

    October 30, 2012 at 9:03 am

    Right! So glad for the confirmation. Maybe it has to do with the electin or something.

     

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