Wednesday, November 30, 2022

Bamboo, Bamboo Look-Alikes, and a 'Miracle' Grass at the Harry P. Leu Botanical Garden

Bambusa vulgaris 'Vittata' (Striped Timber Bamboo)

Bamboos form the subfamily Bambusoideae, and there is no doubt that they are some of the most beautiful grasses around. Their colorful culms, delicate leaves, and the majestic heights reached by some bamboo species, make them a favorite of many plant collectors and  growers, and their economic importance as structural materials is second to none in the Poaceae. In addition, bamboos hold a special place in the cultures of many East Asian countries.

Bambusa malingensis (?) dwarfs passersby

I visited the Harry P. Leu Botanical Garden in Orlando, FL and spent some time marveling over these plants, but also discovered a few other new grasses that I had never encountered before.

As always, the bamboos were probably one of the highlights for many of the people visiting the garden.  People were especially enthralled by the larger specimens, which towered over them and rose to reach the heights of the surrounding trees. Unfortunately, even though there were signs that urged people not to do so, I saw instances of culms with the initials of visitors carved into them. 

Bambusa vulgaris

There is a common misconception that the bamboos are the most "primitive" of the grasses (probably due to the fact some are woody), but recent studies show that the Bambusoideae diverged after the rice subfamily (Oryzoideae), and much later than the three earliest grass subfamilies (Anomochlooideae, Pharoideae, and Puelioideae). More on grass phylogeny in some future post, I promise.

Although many of the specimens I found were varieties of Bambusa vulgaris (Timber Bamboo), there were quite a few other species that caught my eye. 

A medium sized bamboo (Dendrocalamus minor 'Amoenus') that had a bluish tint to its culms entranced me.

Dendrocalamus minor 'Amoenus'

I was also interested in a smallish bamboo with the funny name of Pseudosasa japonica 'Tsutsumiana' that was hidden among its towering brethren. Its form and attractive foliage made me think it would make a nice houseplant, if only it stopped growing at a manageable height! But the highlight of my trip turned out to be some of the non-Bamboo grasses.

Pseudosasa japonica 'Tsutsumiana'

A few of the species that were also in the bamboo section of the park looked remarkably like small bamboo, but were in fact not in the subfamily Bambusoideae at all! 

Thysanolaena latifolia

Thysanolaena latifolia (called Tiger Grass in some places, and Broom Grass in others) had elegant broad leaves, and I thought at first it was another bamboo. The specimen I found in the shade sported dried flowerheads that looked like brooms, and in their native habitat they are in fact used for sweeping.

Thysanolaena latifolia seedheads

Another grass that really caught my attention was a small cutie that only reached to my calf called Pogonatherum paniceum. It looked like a bamboo as well, and it had gorgeous striped leaves and an attractive roundish habit. It is used as an ornamental in some places, and I have a feeling I might get one for my garden someday.

Pogonatherum paniceum

One other specimen that held my attention showed up near the end of my visit. The day was coming to a close, and I was hurrying towards the exit when I came upon an entire section that was dedicated to ornamental, and other, grasses.

In addition to the usual ornamental grass suspects like Miscanthus spp, as well as economically important species like Saccharum officinarum (Sugarcane), the lot had a species that I had been hearing about a lot in my sojourns on facebook, but which I had never seen in person.

Chrysopogon zizanioides (Vetiver grass) habit

Chrysopogon zizanioides, which is also called Vetiver grass, is a species which has its own groups in Facebook, and its many economic benefits has been been touted loudly and repeatedly by its many boosters around the world.

Chrysopogon zizanioides (Vetiver grass) seedheads

C. zizanioides is considered part of a low cost technology solution that has helped to solve various problems. It has a massive root system that grows vertically and deep into the soil, which makes it ideal for erosion control. These same roots also spread and slow down runoff so it passes harmlessly across farmland, and the ability of the grass to tolerate very high levels of heavy metals makes it ideal for soil remediation. It is also used for pest control in that it is attractive to many insect pests (e.g. stem borer moths), which lay their eggs on the plants instead of nearby crops. The larvae who feast on C. zizanioides die due to chemicals in the grass that interfere with their digestive system.

It really is  a so-called 'Miracle' Grass to the many people around the world who have used it! 

Here are some of the species that I discovered and mapped by GPS in the Harry P. Leu Botanical Gardens:

Bamboo:

Bambusa dissimulator
Bambusa eutuldoides 'Viridivittata'
Bambusa malingensis
Bambusa multiplex
Bambusa multiplex 'Golden Goddess'
Bambusa oldhamii
Bambusa textilis var gracilis
Bambusa vulgaris
Bambusa vulgaris 'Vittata' 
Dendrocalamus asper
Dendrocalamus minor 'Amoenus'
Otatea fimbriata
Pseudosasa japonica 'Tsutsumiana'

In addition to the bamboos, I was happy to find some Other Grasses:

Arundo formosana
Chrysopogon zizanioides
Miscanthus spp
Pogonatherum paniceum
Thysanolaena latifolia
Saccharum officinarum
Trypsacum spp

...and a few more that I had no time to survey due to the park closing.

For visitors to the park later, I created a google map of the specimens that I found. You can find it here:



Monday, November 21, 2022

Letting Your Lawn Grasses Flower

Stenotaphrum secundatum (St. Augustine Grass) flowerhead with orange anthers and purple stigmas

Notwithstanding the growing complaints about lawns, a lawn of turf grass has some aesthetic  qualities. Lawns are clean looking to some people, and they project a sense of ordered structure that a mélange of different plants squeezed together might not.

Paspalum notatum (Bahiagrass) with purple anthers and stigmas

But aside from a few weedy species like Poa annua that thwart the mower's blades by flowering close to the ground, the various turf grass species are kept from showing their full reproductive selves by the regular mowing that homeowners do. This incessant desire to keep the lawn grasses short prevents the grasses from pushing up flowerheads and scattering pollen and seeds to the winds, while making it difficult for homeowners to identify the grass from just their vegetative structures.

Zoysia matrella with tiny spikelike flowerheads

Most turf grasses have relatively tiny inflorescences, a consequence of the fact grasses are wind-pollinated and have no need to expend energy on unneeded colorful petals and sepals. In addition, turf grasses are usually species which have evolved to be grazed, so they eschew tall stalks and flowerheads and keep close to the ground. 

But it is still fascinating to see the usually colorful stigmas and anthers via some magnification, and by setting aside parts of the lawn as temporary no-mower areas, owners can finally see the turf grasses flower, as well as type them more accurately to species.

Eremochloa ophiuroides (centipede grass) with silvery stigmas and purple anthers

So take some time to see what the flowers of your own lawn looks like. Make at least some part of your lawn no-mow until the tiny flowerheads and seedheads rise up to scatter your lawn's grass seeds to the wind.


Friday, November 11, 2022

Stepping into Prairie Grasses: An Introduction & Primer

Schizachyrium scoparium (little bluestem) inflorescence

The Missouri Prairie Foundation was kind enough to invite me to write an article introducing people to the prairie grasses. I am not an expert, but I spent some time making diagrams of grass structure and macrophotographs of  some of the major tallgrass prairie species.

You can read it here (a PDF file, starting on page 14). Enjoy!

MISSOURI PRAIRIE JOURNAL VOL 43:3-4


Saturday, November 5, 2022

The Armored Spikelets of Sandburs and Sandspurs (and how one became a part of me)

Burs/Spikelets of Cenchrus echinatus

One of my favorite group of grasses are the so-called sandburs or sandspurs.

These are species in the genus Cenchrus, and they sport spikelets ensconced in armored, thorned burs. There are usually several spikelets nestled within the shell.

A single inflorescence of C. echinatus 

I find the resulting structures (which are sometimes vividly colored) attractive in a dark and deadly way; botanical weaponry that is achingly beautiful in its form and function.

But the main function of the burs is actually more mundane, as they are principally used to disperse the seeds of the plant via animal hosts. The thorns frequently catch onto the skin or clothing of some passing host, and the entire bur is then carried far away from its original location. There have also been studies that show the bur floats and aids in dispersal via water.

Less mature burs/spikelets of C.echinatus

I encountered sandburs in NJ, and also in the Philippines. In both cases, the species was not in abundance in the area, but the small stature of the grass (and its annual nature) might cause one to underestimate their prevalence.

I finally came upon a sandbur species here in Florida while walking between homes that were under construction. The plants were in a sunny location in what would be the front lawn in the completed home.

I typed it as Cenchrus echinatus (which is called Southern Sandbur in some places here), based on the globular, pubescent bur, which has upper (inner) spines fused at the lower part and a ring of bristlelike lower (outer spines) near the base.


In my eagerness to take photographs of the cluster I accidentally brushed against one of the seedheads and a bur stuck to my right middle finger. I absently brushed it off, and was annoyed to discover the spine had broken off and was still lodged in my skin. 

When I got home and my wife and I tried to remove it, we found out that the spine had penetrated deeper than we thought, and it was impossible to dig it out without creating a deeper wound. When I visited a doctor later, she could not make it out (and I did not feel it when she applied pressure on the area), so she decided to leave it in and said that the small piece would be pushed out by my body as it repaired the wound.

And so now, not only am I made mostly from grass because of the food that I eat, but I probably have weaponry from a grass forever lodged under my skin. I truly am becoming an Orang Poaceae!

Monday, October 31, 2022

Mass Flowering of Native C4 Grasses in a Florida Savanna

Andropogon ternarius (syn. Andropogon cabanisii)

Update: Thanks to an unknown commentator and the infernal never ending work of taxonomists, the following corrections are added - the Andropogon ternarius depicted is synonymously termed Andropogon cabanisii, while the Andropogon glomeratus here is Andropogon tenuispatheus, which is synonymous with Andropogon glomeratus var. pumilus. 

Update 2: Added comments and pics of Saccharum giganteum.

The passing of the seasons can be seen in the regular changes in the grasses that make up a landscape. Even here in subtropical Florida, the coming of Fall heralds the flowering of many of the C4 grasses that dominate the longleaf pine savannas that are a marvelous (but threatened) fixture of the natural environment. 

Andropogon glomeratus (syn. Andropogon tenuispatheus)

I visit the Nature Conservancy's Disney Preserve in Kissimmee fairly regularly, and during my visit this late October, the surroundings were suddenly aglow with the sudden flowering of several C4 grasses. 

If you remember from earlier posts, C4 grasses have a specialized carbon-concentrating photosynthetic mechanism that allows them to be more efficient in hot and arid conditions, and they tend to grow fastest and flower during the latter parts of the season. 

Andropogon ternarius (syn. Andropogon cabanisii)

Whereas before, the preserve was a somewhat monotonous landscape of Serenoa repens (saw palmetto) and various smaller grasses like Aristida beyrichiana, with longleaf pines interspersed at almost regular intervals, now the area was dominated by the visually arresting inflorescence of different Andropogon spp. and a few other C4 grasses.,

Sorghastrum secundum

I admittedly am still learning how to identify the many Andropogon spp, but there were a few species that stood out enough that even I was able to identify them. Among the most beautiful was Andropogon ternarius (locally called Splitbeard Bluestem in this area, syn Andropogon cabanisii). Each inflorescence contained a pair of silvery racemes that formed a distinct V, with the awned spikelets giving it a beautiful feathery appearance.

Sorghastrum secundum

Some other Andropogon spp that were in flower included A. glomeratus (Bushy Bluestem, syn Andropogon tenuispatheus), A. virginicus (Broomsedge), and others that I cannot yet identify to species. 

Sorghastrum secundum flowerheads rise up from the understory

An interesting new grass that I found was Sorghastrum secundum, which is related of course to the more well known Sorghastrum nutans (locally called Indiangrass). Unlike S. nutans, the spikelets in S. secundum are all located to one side of the raceme, and this gave rise to one of the local names for it, Lopsided Indiangrass.

Sorghastrum secundum with mostly detached spikelets

But perhaps the most beautiful species that graced the preserve during my visits was Muhlenbergia sericea. This grass is also known as Muhlenbergia capillaris var filipes, and known locally as Gulf Muhly and Sweetgrass.

Muhlenbergia sericea (capillaris)

The purplish inflorescence waved easily in the breeze, and looked almost ethereal when seen in front of the sun's bright rays. M. sericea and its relatives are used often as ornamental grasses here in the peninsula, although I noticed that there is a hit and miss quality when it comes to the lavishness of its flowering in cultivation.

Muhlenbergia sericea (capillaris) line the hiking trail

People were not the only ones appreciative of this species. I also saw a juvenile alligator hiding in the shade of one of the M. sericea specimens (see image below).

An alligator under Muhlenbergia sericea

Perhaps most remarkable of all were vast fields of Saccharum giganteum (locally called Sugarcane Plumegrass), which lay behind rows of Andropogon glomeratus that lined the road leading in and out of the preserve.

Andropogon grasses were in abundance at the preserve (forefront). The tall grasses behind it in the far distance were Saccharum giganteum.

I could not identify them at first due to the distance, but after an unknown commentator mentioned the name, I later came back and waded into the field and took pics.

Saccharum giganteum

The culms and sheaths were quite hairy, and so too were the flowerheads. Macroshots revealed that the spikelets had a ring of long white hairs rising from the base, and straight awns that nailed the ID as S. giganteum.

Saccharum giganteum flowerhead. Inside pic shows expansion of the inflorescence against an aroid backdrop.
Saccharum giganteum spikelet showing long callus hairs and awn.

In the end, there were quite a few species that were in flower that I could not identify at the time. This was especially true for the Andropogon spp, which I am still learning about. Nevertheless, I'll be sure to drop by again soon to continue my exploration of this beautiful grassland, and perhaps someday I'll be able to name all the various species I encounter.



Saturday, October 22, 2022

It's Corn! A Kid and His Love for a Big Lump with Knobs


I admit I do not follow current fads, and I am definitely not on TikTok, Instagram, or most of the various social media channels out there. 

So it took me awhile to discover this interesting and funny meme that had taken first TikTok by storm, and then various other media outlets, including some mainstream news channels (where I finally found it).

A kid named Tariq was interviewed about his liking for corn, and his enthusiasm and love for it was captured later in a song that went viral (view video above).

Watch it and the original interview below and you'll be singing praises as well to corn/maize (Zea mays), which is definitely one of the most important grasses in the world.
 
The original interview:


Thursday, October 20, 2022

Halloween Horrors in the Cornfields

Yeah, Zea mays (maize/corn) can be spooky

It's that time of the year again when pagan rituals (aka Halloween) sweep across this land, and in honor of that occasion I just have to list some of the horror movies that have made cornfields one of the least likely places to visit during night time.

I remember mentioning that I get spooked hiking forests at night, but I think being stuck in a field with tall grasses like corn would not be Disney time either.

We'll start with the better one of the lot - the movie adaptation of Stephen King's short story.

Children of the Corn (1984 original + all the sequels)


But here are more goodies that I dug up from youtube (in year descending order). I cannot vouch for their quality (other than Signs, Jeepers Creepers, and Escape the Field, which were ok), but if you're into dark and dangerous cornfields (and scarecrows!), you'll probably dig most of them.

This next one actually looked good, and was released by Lions Gate, a major studio. I dug it up (yes, I know I used the term "dig" twice...because Halloween) as a streamed movie in my cable lineup and watched it after posting this. It was ok, though the ending might be confusing. Reminds me of the 2010 Predators movie mixed with King's In the Tall Grass (more on that later).

Escape the Field (2022)

This next one is also in one of the streaming services, but it looks so horribly campy that I am giving it a pass.

Sharks of the Corn (2021)

The next several movies I have not seen, nor am I probably ever going to watch them (except for 1922 maybe, which is based on a Stephen King story).

Scarecrows (2018)

1922 (2017)

Husk and sequels (2011)

The Fields (2011)

A Brush with Death (2007)

Dark harvest (2004)

I watched this one a while back by M. Night Shyamalan and it was good drama, but probably not as good as his Sixth Sense, which was a classic.

Signs (2002)

Jeepers Creepers and sequels (2001)

Psycho Scarecrow (1997)- Full Movie


Finally, we'll end with another adaptation of a Stephen King work. No cornfields this time, but a field of another tall grass (Miscanthus spp in real life it turns out) that is just as deadly.

In the Tall Grass (2019)


Happy Halloween!


Monday, October 17, 2022

Beauty and the Beast: The Alligator and the Muhly

 

Gorgeous specimens of Muhlenbergia sericea along the sides of the trail

There is no doubt that species in the genus Muhlenbergia are some of the most beautiful grasses out there, and I mostly encountered them as ornamental grasses in the Northeast USA. But they exist in plentiful varieties as native plants in Florida, a fact that astonished me when I first encountered them in Jacksonville's Atlantic Beach

This group of grasses are also a prominent fixture in the Nature Conservancy's Disney Preserve in Florida, and when I visited the place to hike a couple days back, they were garbed in masses of absolutely gorgeous pinkish blooms.

Juvenile alligator hiding under the beautiful M. sericea

They also seemed to provide an unusual service to the other inhabitants of the park.

Under one large specimen, a juvenile alligator had parked itself under the heavy shade (see image above), perhaps seeking protection from the gawking passersby and other hikers around it. The combination of the airy pink blooms and the primeval looking reptile was striking. 

Beautiful inflorescence of M. sericea

I typed the species to Muhlenbergia sericea, which in some circles is still grouped as a variety of M. capillaris (M. capillaris var. filipes). At the non-macro level, the inflorescence of many of the Muhlenbergia spp look similar, but a closer look at their extremely miniscule spikelets will normally allow people to differentiate between the species.

Spikelets of M. sericea

Unlike the spikelets of M. capillaris, those of  M. sericea have two very long awns (see image below). Both glumes (the outer bract-like structures enclosing the floret) are awned, with one of the glumes having a very long awn. The second long awn is from the lemma, another bract-like structure that holds the male and female reproductive organs of the floret.

Two spikelets of M. sericea, each with with two very long awns. One spikelet is showing purple anthers and the filament, as well as the fuzzy stigma. 

Seeing an alligator is not that unusual in Florida (although this was the first time I've seen one in a bit), but happening upon a gator and a grass (which is in full glorious bloom) certainly is unusual and picturesque.

Wednesday, October 12, 2022

Winter is Coming: How Grasses Conquered the Long Freeze

Tundra (By Education Specialist)

There are vast areas of the world where cold temperatures create problems for plants.

Such "cold stress" happens when temperatures that are below what are optimal for plants creates physiological problems for the individual plants. Depending on the species, optimal growing conditions usually hovers between 10℃ and 30℃. 

There are two types of cold stress, depending on the temperatures involved.

Chilling refers to cold stress where the temperatures range between 0℃ and 15℃, whereas freezing refers to cold stress where the temperatures are below freezing (0℃). 

In the case of freezing, plants can respond via two different methods. Freezing avoidance is when the plant is able to delay or even prevent freezing altogether in their tissues. In contrast, in freezing tolerance, the plants do not prevent ice crystal formation, but they avoid damage by controlling the size of the crystals and/or where the crystals are formed. Freeze-tolerant plants can survive even freezing of their tissues, and represent the extreme adaptation to conquering the cold over long time periods.

Deschampsia antartica (c) Lomvi2 - Wikipedia

Grasses initially evolved as tropical plants that loved the warmth. But over time, the grasses have managed to adapt to the cold and have become the most widespread vascular plant family, and present in all continents. Indeed, the grass Deschampsia antartica is only one of two vascular plants that are native to Antarctica, and its optimal growing temperature is an amazing 10℃!

Freezing can kill grasses via the formation of ice crystals. At first, ice crystals form in the extracellular spaces between cells, which causes water to be pulled from the cell interior. The loss of intracellular water (and later solutes) results in dehydration and osmotic stress. As ice crystals continue to form into the interior of the cells, the cell membranes start to degrade and programmed cell death occurs.

The evolution of the ability to tolerate freezing in the Poaceae is fascinating, and is confined mostly to species in two different subfamilies of the Poaceae. Grasses in the subfamilies Pooideae (in the Northern Hemisphere) and Danthonioideae (in the Southern Hemisphere) live in cold temperate continental regions, and they have solved the problem in two different ways. 

Hordeum jubatum of the subfamily Pooideae (Northern Hemisphere)

The grasses in subfamily Pooideae in the Northern Hemisphere all use the C3 mode of photosynthesis, and are commonly called the cool season grasses. They include many turf grasses (such as Poa pratensis or Kentucky Bluegrass), as well as food staples such as Triticum aestivum (wheat), Avena sativa (oat), and Hordeum vulgare (barley). 

The ancestors of the Pooideae evolved about 67 million years ago in small niches during the formation of the Eurasian mountain ranges. In this group, ice binding proteins evolved which decreased the rate of the formation of ice, as well as altering the shape of the ice crystals being formed. These anti-freeze proteins prevent the formation of large crystals that can physically damage cells and tissues.

Cortaderia selloana from the subfamily Danthonioideae (Southern Hemisphere)

In contrast, cold-acclimated grasses from the subfamily Danthonioideae in the Southern Hemisphere have evolved a different method for conquering the cold. The members of this group are also C3 grasses, and include the large ornamental grass Cortaderia selloana (Pampas grass). The freeze tolerant members of this subfamily produce ice-nucleation proteins that allow them to control where ice crystals form. Thus, they can prevent damage by limiting crystal formation in the extra-cellular spaces and the leaf surfaces, but not within the cell interiors.

The independent evolution of such mechanisms by the Danthonioideae and Pooideae to tolerate freezing have enabled grasses to dominate large areas where there are extreme seasonal fluctuations in temperature, and contributed to the grassy world we live in today. 

As an interesting aside, at the other end of the temperature spectrum, C4 grasses such as those in the grass subfamilies Chloridoideae and Andropogoneae - which include corn/maize (Zea mays), the bluestems (Andropogon spp), sugarcane (Saccharum officinarum), and cogon grasses (Imperata cylindrica) - have extended the range of environments conquered by the Poaceae to much warmer and drier climes. 

For a quick look at the difference between C3, C4 and CAM photosynthesis in grasses, click here.

Muhlenbergia sericea of the subfamily Chloridoideae, a C4 grass

Finally, to read more about the fascinating topic of cold adaptation in grasses in depth, check out the references below.

Note: In addition to the specialized mechanisms of freezing tolerance above, grasses can deploy other additional mechanisms for coping with the cold that are beyond the scope of this shirt post, such as accumulating fructan in their vacuoles, using supercooling (for shorter cold spells), and increasing anti-oxidant enzymes.

Phalaris arundinacea of the subfamily Pooideae

References:

Timothy J. Gallaher, T. J. Gallaher, Paul M. Peterson, P. M. Peterson, Robert J. Soreng, R. J. Soreng, Fernando O. Zuloaga, F. O. Zuloaga, De-Zhu Li, D. Li, Lynn G. Clark, L. G. Clark, Christopher D. Tyrrell, C. D. Tyrrell, Cassiano A.D. Welker, C. A.D. Welker, Elizabeth A. Kellogg, E. A. Kellogg, & Jordan K. Teisher, J. K. Teisher. (2022). Grasses through space and time: An overview of the biogeographical and macroevolutionary history of Poaceae. Journal of systematics and evolution, 60, 522-569. doi: 10.1111/jse.12857

Schubert M, Humphreys AM, Lindberg CL, Preston JC, Fjellheim S. 2020. To coldly go where no grass has gone before: A multidisciplinary review of cold adaptation in Poaceae. In: Annual Plant Reviews online.Wiley.523–562.

Thursday, October 6, 2022

The Mysterious Mound in Split Rock (Pennsylvania)

The mysterious grassy mound at Split Rock. The rock formation is behind it, hidden by trees.
Hidden behind a veil of tall trees in deep Pennsylvania lies Split Rock, a gargantuan rock with a cleft in its middle.

We stayed at the nearby Split Rock Resort and Lake Harmony last month and took one day to visit this strange rock formation, which was created 300 million ago when glaciers swept across the land and also created Lake Harmony.

Drone view of Split Rock with the cleft near middle
The rock itself was fascinating, and you can access the top by climbing up a wooden platform. But another thing that caught my eye as we walked from the parking lot was an equally strange small hill or mound that lay to the side of the formation. It was almost dead center in a clearing, surrounded by trees.

It was also covered in grass, but not turf grass. Instead, I noticed Panicum virgatum (switchgrass) and another species that I at first thought was Schizachyrium scoparium (Little Bluestem).

P. virgatum spikelets
The P. virgatum had beautiful purplish spikelets, with purple fuzzy stigmas and orange anthers.

P. virgatum spikelet showing purple stigmas and orange anthers
The other notable species I found was something that I at first thought was S. scoparium. It had fluffy flowerheads and a similar habit to that species.

A.virginicus seedheads
But when I used macro on the spikelets, the first thing that was noticeable was the very long and straight awns. S. scoparium has awns, but they are noticeably bent, and I decided that what I was seeing was Andropogon virginicus, which is a robust species that is even common in disturbed areas.

For more on the spiketlets of the beautiful S. scoparium, click here.

A. virginicus spikelet. (A) Sessile fertile floret with long awn. (B) Sterile floret on a stalk. (C)  Disconnected raceme connection to the other spikelets.
I have no idea how this mound was formed, or even whether it is a natural formation or one that was man-made. When I was there and it was getting into dusk, the entire place felt dark and otherworldly, and I could not help but wonder whether some eerie rituals were held atop this grassy knoll. The somber lighting, dark forested location, and weird clearing would be perfect for some Hollywood horror film. 

If you ever visit this area in Pennsylvania, then take some time to get a glimpse of this mysterious mound with its trove of native grasses, and the riven rock behind it. Just don't do it in the dark!