Andropogon (and Schizachyrium)

Poaceae

Today’s sunny fieldtrip took John and George through the north end of Seabranch State Park near Hobe Sound, Florida, the present epicenter of our green interests.  Today’s word to describe the glory of nature: Bluestem Grasses!

All Bluestem Grass photos today by John Bradford.

These are those large puffy-topped grasses, sometimes over 6 feet tall so pretty in October.  Always reluctant to pick favorites, apply tickle-torture and I may confess preference for those gorgeous wands of puff.  It isn’t just the silvery tops dancing in the breeze, but also the array of foliar colors.  So autumnal, a celebration of sunbeams and flickering memories, such as fond recollections of childhood strip mines.

I grew up in West Virginia immediately across the Ohio River from bigtime earth-rape.  Bluestems restore a tentative wisp of beauty to the toxic post-mining landscape.  (“Restoration,” yea sure.  Let’s go see the phosphate mines here in Florida.)  CLICK to see a Bluestem (“Broomsedge”) consoling an old mine crater in Illinois.

Bluestems make all the difference along roadsides, in old abandoned farm fields, along railroad tracks, and on rocky hilltops across much of North America and worldwide.  By the way, grouse like them.  Here is a Bluestem enhancing John’s path of life.

Several species coexist locally.  If you are nutty enough to try to sort them out, try our grassy web site.   Distinguishing these species can be extra-exasperating because:  1. The common species can be bewilderingly variable.  2. Different nearby regions house different species assortments.  3. Some hybridize.  4. They do not stick to their textbook habitats or to field-guide dimensions.  So for today, they’re just all “Bluestems.”

Andropogons usually have two bunny-ears.

As hinted a moment ago, they tolerate the world’s worst soils:  graded roadsides, rocky hilltops, hellish railroad tracks, and scrub.  These rugged grasses have a few tricks, some of them studied in only one or few species.

Trick #1.  Some Bluestems have symbiotic root fungi (mycorrhizae) procuring phosphorus from shamefully nutrient-poor soils.

Trick #2.  Bluestems suppress potentially competing vegetation.  It is not mere competition.  Recent research shows some to diminish the “normal” nitrogen-fixing (fertilizer-providing) bacterial associates of non-grass species.

Grasses are turning out increasingly to have their own symbiotic arrangements with unconventional nitrogen-fixing bacteria.  Although data are sparse and preliminary, Bluestems sometimes have such unconventional nitrogen-fixers.  So could they sabotage the other guy’s nitrogen relations while enhancing their own, making the Bluestems kings of the starved soils?  Can they form a nitrogen monopoly?

Even weirder, one species preferentially takes up its soil nitrogen as ammonia, as opposed to slurping in nitrate, the other form in which plants take up nitrogen.  The selfish Bluestem is able to diminish soil nitrate to the detriment of potential competitors, while it somehow enhances soil ammonia for its personal private consumption.